10,879 Matching Annotations
  1. Aug 2020
    1. Note that not all claims of policy give details or specifics about what should be done or how. Sometimes an author is only trying to build momentum and point us in a certain direction.

      Good to know.

    1. that the centrifugal force of the revolving electron just exactly balances the attractive force of the nucleus (in analogy with the centrifugal force of the moon in its orbit exactl

      kriuyoouoouuiouooui

    1. Several web sites are already using the widgetized PubChem Periodic Table and a notable example is LibreTexts (https://libretexts.org/), which is an open education repository. It uses the PubChem Periodic Table within a reference table page (https://chem.libretexts.org/Bookshelves/Ancillary_Materials/Reference/Periodic_Table_of_the_Elements), which is provided as a supplement to free online chemistry course materials.

      Widgetized Periodic Table in LibreTexts

    1. Nutrient Functions Carbohydrates Provide a ready source of energy for the body (sometimes referred to as the preferred source of energy for the body). Provide structural constituents for the formation of cells. Lipids (Fats) Provide stored energy for the body. Function as structural components of cells and also as signaling molecules for proper cellular communication. Provide insulation to vital organs and works to maintain body temperature. Proteins Necessary for tissue formation, cell repair, regulating fluid balance, and hormone and enzyme production. Essential for building strong muscles and a healthy immune system. Water Transports essential nutrients to all body parts, transports waste products for disposal, and aids with body temperature maintenance. Vitamins Regulate body processes and promote normal body-system functions. Minerals Regulate body processes, are necessary for proper cellular function, and comprise body tissue.

      6 nutrients and their functions

    2. To measure the number of kilocalories in a particular food substance, a certain amount of food is burned in a device called a calorimeter. As the food burns, heat is created. The heat dissipates to the surrounding water while a thermometer detects the change in temperature of the water.

      how to measure the number of kilocalories

    3. Minerals Major Functions Macro Sodium Fluid balance, nerve transmission, muscle contraction Chloride Fluid balance, stomach acid production Potassium Fluid balance, nerve transmission, muscle contraction Calcium Bone and teeth health maintenance, nerve transmission, muscle contraction, blood clotting Phosphorus Bone and teeth health maintenance, acid-base balance Magnesium Protein production, nerve transmission, muscle contraction Sulfur Protein production Trace Iron Carries oxygen, assists in energy production Zinc Protein and DNA production, wound healing, growth, immune system function Iodine Thyroid hormone production, growth, metabolism Selenium Antioxidant Copper Coenzyme, iron metabolism Manganese Coenzyme Fluoride Bone and teeth health maintenance, tooth decay prevention Chromium Assists insulin in glucose metabolism Molybdenum Coenzyme

      minerals and their major functions

    1. one study does not substantiate a fact.

      one study does not substantiate a fact

    2. Who sponsors the website? Look at the website extension (.com, .edu, .gov, .org); typically .com websites are considered to be less credible than websites with other extensions. Are you being sold something at this website? Are author names and credentials disclosed? If so, do the authors have the educational background and/or expertise required for the topic? Is an editorial board identified? Are experts reviewing the content of the website for accuracy and currency? Does the site contain links to other credible informational websites? Even better, does it reference peer-reviewed journal articles? If so, do those journal articles actually back up the claims being made on the website? How often is the website updated? Does the website charge a fee?

      Who are the sponsors Are the author names and credentials listed Editorial Board identified? Does the cite contain links to other credible sites How often is the website updated? Is the site free of charge?

    1. Agreement involving many experts across multiple scientific disciplines is necessary for recommending dietary changes to improve health and prevent disease

      Along with studies and trials, there has to be some kind of common consensus among a swathe of professionals for it to enter public domain as common practice or course

    1. There is an element that we need more of in our bodies than is proportionately present in Earth’s crust, and this element is not easily accessible.

      Curious to see phosphorus levels over time from as early as possible. The increase in human population must make phosphorus levels almost minuscule. I'm assuming most animals require phosphorus as well but how much in comparison to humans.

    1. proteins in the plasma membrane assist other substances in crossing the membrane.

      role of protein molecules

    2. Molecules of cholesterol help the plasma membrane keep its shape.

      role of lipid cholesterol

    1. sde

    2. paign trail in 2015 and 2016, U.S. Democratic presidential candidate Bernie Sanders was feeling the burn — sunburn, that is. There’s no doubt that candidate Sanders was exposed to a lot of UV light during all those outdoor rallies in states across the nation. Exposure to UV light is the single greatest risk factor for skin cancer, so it’s perhaps not surprising that Sanders was diagnosed with a small skin cancer on his cheek by December of 2016 (although most of his cumulative UV exposure probably occurred earlier in life). In Sanders’ case, the cheek cancer was a basal cell carcinoma. This is the most common type of skin cancer. Fortunately, basal cell carcinoma is also a slowly growing and highly curable cancer. Sanders had his basal cell carcinoma completely removed in an hour-long outpatient procedure, after which he was able to return i

      test

    1. Atomic theory states that matter is composed of discrete units called atoms, as opposed to the obsolete notion that matter could be divided into any arbitrarily small quantity. It began as a philosophical concept in ancient Greece (Democritus) and India and entered the scientific mainstream in the early 19th century. It was during this time when discoveries in the field of chemistry showed that matter did indeed behave as if it were made up of particles.

      LibreTexts-Query-1214

    1. enthalpy

      total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume.

    2. Adiabatic

      An adiabatic process occurs without transferring heat or mass between a thermodynamic system and its surroundings. Unlike an isothermal process, an adiabatic process transfers energy to the surroundings only as work.

  2. math.libretexts.org math.libretexts.org
    1. What are the factors?

      The numbers that are easily divisible to another number are known as factors of a number. For example, the factors of number 12 are:

      12 = 2x6 or

      12 = 3x4 or

      12 = 2x2x3

      What is factoring?

      Factoring is a complete process of finding out the factors of a particular numeral expression. Factoring trinomials means to find the exact numbers that can be multiplied to get a certain output.

      In order to factor an expression, it is mandatory to find the greatest as well as the common factor of the expression. Make sure to look for the highest common factor that can get the job done by dividing all of the numbers of the expression, evenly.

      Tracked attributes to Manual Factorization

      Manual factorization can be troublesome for many individuals, but we can make it really easy and understandable with the help of continuous practices. A factor phrase can be easily simplified with the help of manual leads to a detailed orbit. The factorized phrase can be consisting up to three integers, and it can be simplified using the concept of mn, mk, and k*n. These attempts may be unpredictable at times, which may lead to some unrelatable results. With the use of some tricks, exact factors can be pitched at the end of the process. For example, quadratic equations, when needed to factorize, usually expand. After expansion, factor results may be 1-2 step processes.

      So, more attention can be drawn regarding integral simplification with the help of manual factorization. As far as digital learning is concerned, it will provide exact results without losing attention.

      If you have enough tools (smart tools) and calculators, digital factorization will be more than easy for you. With the help of digital factorization, you will be able to track your best conclusions and manage distribution entirely for even the complex equations.

      For example, if we submit a mathematical phrase x²+5x+4 in the solution bar of a factor calculator, the result will be (x+1)(x+4). The result has been obtained by:

      Adding two numbers to obtain 5

      Multiplying two numbers to obtain 4

      As far as digital copying is concerned, you have to scroll down and go to the next page. Whereas, you can read the manual formulation at first glance. Those users who are unaccustomed to reading on-line or who prefer using laptops and computers tend to be more comfortable reading paper-based manuals. One of the things about paper-based manuals is that they are already printed along with all the procedures, which is why they can’t be updated and revised. On the other hand, digital practices are there that can be updated or revised anytime. This is something where digital practices are more compatible. It depends on your intended goals, whether you need paper-based factorization or digital factorization. The use of those factorization procedures also depends upon the purpose of manual keeping in mind your intended goals.

      The best thing about these calculators is, they can record the description for a particular question. It depends on the user whether he/she requires the final result or the detailed results.

      In order to get exact and accurate values, one should rely on digital calculators. Digital calculators are also easy to use, and there are so many custom online digital and factor calculators available one can use for digital calculations.

      These factoring calculators can discover the factors and factor matches of a positive or a negative number just like this factorial calculator. Before starting to use these factorization calculators, always make sure to know about the essential margins and probed knowledge of typical brain investment.

      In order to get accurate results within nano-second, use factor calculators. Factor calculators are trending these days as far as retaining the digital or smart information is concerned.

  3. Jul 2020
    1. horst is an upthrown block between oppositely dipping normal faults. A graben is a downthrown block between oppositely dipping normal faults. A half-graben is the tilted hanging wall basin of a normal fault.

      K

    1. y Pi as an internet hot spot and loads the computer with a variety of OERs, including LibreTexts. Because the dev

      demonstation

    1. V2=M1V1M2=(0.0452)(0.045)0.0955=21.2mL(20)(20)V2=M1V1M2=(0.0452)(0.045)0.0955=21.2mLV_2= \dfrac{M_1V_1}{M_2} = \dfrac{(0.0452)(0.045)}{0.0955} = 21.2\; mL Therefore it takes 21.2 mL of Ba(OH)2Ba(OH)2Ba(OH)_2 to titrate 45.00 mL HNO3HNO3HNO_3.

      THIS PART IS wRONG, Ba(OH)2 has two OH- groups so needs to be divided by 2

    1. e r

      It isn't clear what the roots are supposed to be. For the experienced reader it is completely obvious, but for the beginner this may occasionally cause problems: "...where r_1 /neq r_2, then r_1, r_2 are the two distinct..."

    1. Cannizzaro reaction

      Important Note: The reaction is mostly seen in the case of aldehydes and ketones having no α hydrogen and are put in strongly basic conditions. It is basically a disproportionation reaction i.e., the same molecule gets reduced and oxidised simultaneously. In case of Cross and Intramolecular Cannizzaro reaction, the bulkier group gets reduced while the other one gets oxidised. The hydrogen of the hydroxyl group comes from the base it's put into.

    1. Our worldview influences our behaviors. Behaviors endure over time and are passed from person to person. Within a dominant or national culture, members can belong to many different groups. Dominant cultures may be made up of many subsets or co-cultures that exist within them. For example, your dominant or national culture may be the United States, but you are also a thirty-year-old woman from the Midwest who loves poodles. Because you are a thirty-year-old woman, you exist in the world very differently than a fifty-year-old man. A co-culture is a group whose values, beliefs or behaviors set it apart from the larger culture of which it is a part of and shares many similarities. (Orbe, 1996) Social psychologists may prefer the term micro-culture as opposed to co-culture.

      Behavior

    1. Rates of reactions that consume or produce gaseous substances, for example, are conveniently determined by measuring changes in volume or pressure. For reactions involving one or more colored substances, rates may be monitored via measurements of light absorption. For reactions involving aqueous electrolytes, rates may be measured via changes in a solution’s conductivity.

      Rates of reactions are determined by measuring the changes using different measurements

    2. efine chemical reaction rate Derive rate expressions from the balanced equation for a given chemical reaction Calculate reaction rates from experimental data

      Study objectives questions 1-3

    1. Madelung's Rule:

      An apparent of Aufbau's principle Can be used to determine long electron configurations. But cannot be used in application on newly founded(man made) elements like Og (Atm. No.118)

    1. Nuclei with magic numbers of both protons and neutrons are said to be “doubly magic” and are even more stable.

      Ha! Props to whichever PhD came up with the term "doubly magic".

    1. 𝑢′=𝑓(𝑥)𝑦1(𝑥)

      The separation is done in this form, as the differentiated variable u' has been separated from the other kind of variable(s) on the R.H.S.

      This is similar to the definition of a separable diff eq where we write:

      h(y) y' = g(x)

      here too, the variable that involves the differentiation has been separated from the other variable.

    1. If both 𝑓ff and 𝑓𝑦fyf_y are continuous on 𝑅RR

      Theorem 2 (Uniqueness). Suppose that both F(x, y) and \(∂F(x, y)/∂y\) are continuous functions defined on a region R as in Theorem 1.

      Then there exists a number δ2 (possibly smaller than δ1) so that the solution y = f(x) to (), whose existence was guaranteed by Theorem 1, is the unique solution to () for x0 − δ2 < x < x0 + δ2.

    2. 𝑦′=𝑓(𝑥,𝑦),𝑦(𝑥0)=𝑦0

      The general first-order ODE is y0 = F(x, y), y(x0) = y0. __ (1)

      We are interested in the following questions: (i) Under what conditions can we be sure that a solution to (1) exists? (ii) Under what conditions can we be sure that there is a unique solution to (1)? Here are the answers.

      Theorem 1 (Existence). Suppose that F(x, y) is a continuous function defined in some region R = {(x, y) : x0 − δ < x < x0 + δ, y0 − ? < y < y0 + ?} containing the point (x0, y0).

      Then there exists a number δ1 (possibly smaller than δ) so that a solution y = f(x) to (1) is defined for x0 − δ1 < x < x0 + δ1.

  4. Jun 2020
    1. (POB) Methionine Has Only One Codon. Methionine is one of the two amino acids having only one codon. Yet the single codon for methionine can specify both the initiating residue and interior Met residues of polypeptides synthesized by E. coli. Explain exactly how this is possible.

      What is the answer can u help me ?

    1. Obviously, 𝑢uu can’t be constant, since if it were, the left side of Equation 2.1.162.1.16\ref{eq:2.1.17} would be zero. Recognizing this, the early users of this method viewed 𝑢uu as a “parameter” that varies; hence, the name “variation of parameters.”)

      Notice how \(y_{1}\) is only a non-trivial solution of the complementary equation => \( y_{1}' + p(x)y_{1}' = 0\)––––(A)

      We then speculate whether \(y = uy_{1}\) (with u as a constant) is a solution of the non-homogenous eqn. 2.1.16 or not.

      To test this speculation, we put \(y = uy_{1}\) into 2.1.16 Which gives => \(uy_{1}' + u.p(x).y_{1}' = f(x)\)

      But the L.H.S here is merely a multiple of (A) => L.H.S = 0 ≠ f(x)

      Hence, the speculation that \(y = uy_{1}\) with u as a constant is a solution of 2.1.16 is rendered incorrect. u must instead be a function of x.

    1. However, one might think that since the number of valence electrons increase going down the group

      The number of valence electrons does not increase as you go down a group. Did you mean because the valence electrons increase as you go across a period?

      Or did you mean just that because the total number of electrons increases as you move down a group?

    1. Most economies in the real world are mixed economies; they combine elements of private ownership of the means of production and private ownership of the means of production (or socialism and market-based systems).

      The U.S. economy is positioned toward the market-oriented end of the spectrum. Many countries in Europe and Latin America, while primarily market-oriented, have a greater degree of government involvement in economic decisions than does the U.S. economy. China and Russia, while they are closer to having a market-oriented system now than several decades ago, remain closer to the command economy end of the spectrum. There are other nations that have market-based systems that also utilize socialism to promote social welfare such as Sweden and Scandinavian countries.

    2. Market economies have a very decentralized structure. A market is an institution that brings together buyers and sellers of goods or services, who may be either individuals or businesses.

      Market economies are based on private enterprise: the means of production (resources and businesses) are owned and operated by private individuals or groups of private individuals. Businesses supply goods and services based on demand.

    1. cosθ=z(r′2+z2)1/2.

      Unit Vector of direction 'Z'

    2. zz2+R2−−−−−−√z

      This is finding the Unit Vector of Z direction

    3. 2

      This '2' here is the multiple factor that represent both K direction E-fields form left and right segment of the line charge due to symmetry, and it is why you don't need to integrate from -L/2 to L/2

    1. At very large values of r, the electron probability density is very small but not zero.

      As the distance from the nucleus increases, the probability of finding an electron decreases but not zero.

    1. The frequencies of these X-rays are unique to each element, and they increase uniformly in successive elements. Moseley found that the square roots of these frequencies give a straight line when plotted against Z; this enabled him to sort the elements in order of increasing atomic number.

      What's the relationship between the square root of the frequencies of the X-rays to the number of protons? Like how are they related? What's the reason behind their correlation?

    2. by-product of the decay of other radioactive elements.

      How does the decaying of other radioactive elements result to other isotopes? Does the protons disintegrate or separate in order to form another element?

    3. twenty-three of them (including beryllium and fluorine, shown in the table) are monoisotopic

      TRIVIA! 23 are monoisotopic!

      These elements are: Be, F, Na, Al, P, Sc, Mn, Co, As, Y, Nb, Rh, I, Cs, Pr, Tb, Ho, Tm, and Au. In addition, two elements, Bi and Pa, have only one isotope that contributes to the standard atomic weight, but that isotope is radioactive.<br> Source: https://ciaaw.org/monoisotopic-elements.htm

    1. Figure 6.1.46.1.4\PageIndex{4}: Temperature versus heat. The system is constructed so that no vapor evaporates while ice warms to become liquid water, and so that, when vaporization occurs, the vapor remains in the system. The long stretches of constant temperatures at 0oC0oC0^oC and 100oC100oC100^oC reflect the large amounts of heat needed to cause melting and vaporization, respectively.

      Figure 6.1.4 : Temperature versus heat. The system is constructed so that no vapor evaporates while ice warms to become liquid water, and so that, when vaporization occurs, the vapor remains in the system. The long stretches of constant temperatures at 0oC and 100oC reflect the large amounts of heat needed to cause melting and vaporization, respectively.

    2. Heat and work have signs (positive or negative), and the sign of each depends on whether the system we are considering is gaining or losing energy. In this class, if a process makes the system gain energy, qqq and/or www are positive; if the process makes the system lose energy, qqq and/or www are negative. We can put this information into four formal statements: If heat flows into a system, qqq is positive. If heat flows out of a system, qqq is negative If the surroundings do work on the system, www is positive. If the system does work, www is negative.

      Heat and work have signs (positive or negative), and the sign of each depends on whether the system we are considering is gaining or losing energy. In this class, if a process makes the system gain energy, q and/or w are positive; if the process makes the system lose energy, q and/or w are negative. We can put this information into four formal statements:

      • If heat flows into a system, q is positive.
      • If heat flows out of a system, q is negative
      • If the surroundings do work on the system, w is positive.
      • If the system does work, w is negative.
    3. In order to measure energy, we need a unit for it. In the metric system, the standard unit of energy is the joule. The formal definition of a joule is: A joule is the amount of energy expended when an object is moved 1 meter against a resisting force of 1 newton. (You can learn all about the concept of force in a physics class.) As for the joule, here are some statements that may help you visualize this unit.  A joule is… …enough energy to lift a one kilogram object 10.2 centimeters. …enough energy to heat one milliliter of water from 20ºC to 20.24ºC. …enough energy to keep a 60 watt light bulb glowing for 0.0167 seconds. Obviously, a joule is a very small amount of energy, and in fact it is an inconveniently small amount when we describe chemical reactions. Chemists usually report energies for reactions in kilojoules (1 kJ = 1000 J).

      In order to measure energy, we need a unit for it. In the metric system, the standard unit of energy is the joule. The formal definition of a joule is: A joule is the amount of energy expended when an object is moved 1 meter against a resisting force of 1 newton. (You can learn all about the concept of force in a physics class.) As for the joule, here are some statements that may help you visualize this unit. A joule is…

      …enough energy to lift a one kilogram object 10.2 centimeters.

      …enough energy to heat one milliliter of water from 20ºC to 20.24ºC.

      …enough energy to keep a 60 watt light bulb glowing for 0.0167 seconds.

      Obviously, a joule is a very small amount of energy, and in fact it is an inconveniently small amount when we describe chemical reactions. Chemists usually report energies for reactions in kilojoules (1 kJ = 1000 J).

    1. Applications Gas chromatography is a physical separation method in where volatile mixtures are separated. It can be used in many different fields such as pharmaceuticals, cosmetics and even environmental toxins. Since the samples have to be volatile, human breathe, blood, saliva and other secretions containing large amounts of organic volatiles can be easily analyzed using GC. Knowing the amount of which compound is in a given sample gives a huge advantage in studying the effects of human health and of the environment as well. Air samples can be analyzed using GC. Most of the time, air quality control units use GC coupled with FID in order to determine the components of a given air sample. Although other detectors are useful as well, FID is the most appropriate because of its sensitivity and resolution and also because it can detect very small molecules as well. GC/MS is also another useful method which can determine the components of a given mixture using the retention times and the abundance of the samples. This method be applied to many pharmaceutical applications such as identifying the amount of chemicals in drugs. Moreover, cosmetic manufacturers also use this method to effectively measure how much of each chemical is used for their products. Equations “Height equivalent to a theoretical plate” (HETP) use to calculate the flow rate by usingthe total number of theoretical plates (N) and column length (L). Some application, HETP concepts is used in industrial practice to convert number of theoretical plates to packing height. HETP can be calculate with the Van Deemter equation, which is given by HETP=A+Bυ+Cv(1)(1)HETP=A+Bυ+Cv HETP= A + \dfrac{B}{υ} + Cv \tag{1} Where A and B and C are constants and v is the linear velocity (carrier flow rate). A is the "Eddy-Diffusion" term and causes the broadening of the solute band. B is the "Longitudinal diffusion" term whereby the concentration of the analyte, in which diffuses out from the center to the edges.This causes the broadering of the analyte band. C is the "Resistance to Mass Transfer " term and causes the band of the analyte broader. HETP=LN(2)(2)HETP=LN HETP= \dfrac{L}{N} \tag{2} L is the length of the column, where N is the number of theoretical plates, tR is the retention time, and ω is the width of the elution peak at its base. N=16(tRω)2(3)(3)N=16(tRω)2 N= 16 \left (\dfrac{tR}{ω} \right)^2 \tag{3} In which, the more plates give a better resolution and more efficiency. Resolution can be determined by   R=2[(tR)B–(tR)AWA+WB](4)(4)R=2[(tR)B–(tR)AWA+WB]R= 2\left[ \dfrac{(tR)B – (tR)A}{ WA +WB}\right] \tag{4} A relationship between the plates and resolution is giving by, R=(N)1/2/4)(α−1α)(1+K′BK′B)(5)(5)R=(N)1/2/4)(α−1α)(1+K′BK′B) R= (N)1/2 /4) ( \alpha -\dfrac{1}{\alpha}) ( 1+ \dfrac{K’B}{ K’B}) \tag{5} Where the selectivity, a, and k' is the capacity factors take places of the two solutes. The selectivity and capacity factors can be control by improving separation, such as changing mobile/ stationary phase composition, column temperature and use a special chemical effect. References Skoog, D. A.; Holler, F. J.; Crouch, S. R. Principles of Instrumental Analysis. Sixth Edition, Thomson Brooks/Cole, USA, 2007. Krugers, J. Instrumentation in Gas Chromatography. Centrex Publishing Company-Eindhoven, Netherlands, 1968. Hubschmann, H. Handbook of GC/MS: Fundamentals and Applications. Wiley-VCH Verlag, Germany, 2001. Scott, R. P. W. Chromatographic Detectors: Design, Function, and Operation. Marcel Dekker, Inc., USA, 1996. J.N. Driscoll. REview of Photoionization Detection in Gas Chromatography: The first Decade. Journal of CHromatographic Science , Vol 23. November 1985. 488-492. Boer, H. , "Vapour phase Chromatography", ed. Desty, D. H., 169 (Butterworths Sci. Pub., London, 1957). Dimbat, M. , Porter, P. E. , and Stross, F. H. , Anal. Chem., 28, 290 (1956). | Article | ISI | ChemPort | Contributors Kyaw Thet (UC Davis), Nancy Woo (UC Davis) /*<![CDATA[*/ $(function() { if(!window['autoDefinitionList']){ window['autoDefinitionList'] = true; $('dl').find('dt').on('click', function() { $(this).next().toggle('350'); }); } });/*]]>*/ /*<![CDATA[*/ var front = "auto"; if(front=="auto"){ front = "Gas Chromatography"; if(front.includes(":")){ front = front.split(":")[0]; if(front.includes(".")){ front = front.split("."); front = front.map((int)=>int.includes("0")?parseInt(int,10):int).join("."); } front+="."; } else { front = ""; } } front = front.replace(/_/g," "); MathJaxConfig = { TeX: { equationNumbers: { autoNumber: "all", formatNumber: function (n) { if(false){ return front + (Number(n)+false); } else{return front + n; } } }, macros: { PageIndex: ["{"+front+" #1}",1], test: ["{"+front+" #1}",1] }, Macros: { PageIndex: ["{"+front+" #1}",1], test: ["{"+front+" #1}",1] }, SVG: { linebreaks: { automatic: true } } } }; MathJax.Hub.Config(MathJaxConfig); MathJax.Hub.Register.StartupHook("End", ()=>{if(activateBeeLine)activateBeeLine()}); /*]]>*/ /*<![CDATA[*/window.addEventListener('load', function(){$('iframe').iFrameResize({warningTimeout:0, scrolling: 'omit'});})/*]]>*/ Back to top Chromatography High Performance Liquid Chromatography Recommended articles There are no recommended articles. 3.1: Principles of Gas ChromatographyNowadays, gas chromatography is a mature technique, widely used worldwide for the analysis of almost every type of organic compound, even those that a...10.23: ChromatographyChromatography is an efficient way for chemists to separate and analyze mixtures. Read on to find out how this critical process works.2.4: Gas Chromatography (GC)Gas chromatography (GC) is a powerful instrumental technique used to separate and analyze mixtures. A gas chromatograph is a standard piece of equipme...2.4D: Quantitating with GCPeak integrations are useful because it is possible to correlate the area under a peak to the quantity of material present in a sample. Note it is the...2.4A: Overview of GCGas chromato

      application

    1. K. Henry. 8. The first examination of Anne Askew Martyr, before the Bishop.

      In the original folio, headings ran across the top of each page, flagging both the era (in this case, the reign of King Henry VIII) and the topic of the text that followed.

    1. In any electrochemical process, electrons flow from one chemical substance to another, driven by an oxidation–reduction (redox) reaction. A redox reaction occurs when electrons are transferred from a substance that is oxidized to one that is being reduced. The reductant is the substance that loses electrons and is oxidized in the process; the oxidant is the species that gains electrons and is reduced in the process. The associated potential energy is determined by the potential difference between the valence electrons in atoms of different elements.
    1. Theoretical Yields When reactants are not present in stoichiometric quantities, the limiting reactant determines the maximum amount of product that can be formed from the reactants. The amount of product calculated in this way is the theoretical yield, the amount obtained if the reaction occurred perfectly and the purification method were 100% efficient. In reality, less product is always obtained than is theoretically possible because of mechanical losses (such as spilling), separation procedures that are not 100% efficient, competing reactions that form undesired products, and reactions that simply do not run to completion, resulting in a mixture of products and reactants; this last possibility is a common occurrence. Therefore, the actual yield, the measured mass of products obtained from a reaction, is almost always less than the theoretical yield (often much less). The percent yield of a reaction is the ratio of the actual yield to the theoretical yield, multiplied by 100 to give a percentage: percent yield=actual yield (g)theoretical yield(g)×100%(3.7.29)
    1. What happens to matter when it undergoes chemical changes? The Law of conservation of mass says that "Atoms are neither created, nor distroyed, during any chemical reaction." Thus, the same collection of atoms is present after a reaction as before the reaction. The changes that occur during a reaction just involve the rearrangement of atoms.
    2. C7H16(l)+O2(g)→CO2(g)+H2O(g)(3.1.4)(3.1.4)C7H16(l)+O2(g)→CO2(g)+H2O(g) C_7H_{16} (l) + O_2 (g) \rightarrow CO_2 (g) + H_2O (g) \label{3.1.3} The complete combustion of any hydrocarbon with sufficient oxygen always yields carbon dioxide and water. Figure 3.1.23.1.2\PageIndex{2}: An Example of a Combustion Reaction. The wax in a candle is a high-molecular-mass hydrocarbon, which produces gaseous carbon dioxide and water vapor in a combustion reaction (see Equation 3.1.43.1.4\ref{3.1.3}). Equation 3.1.43.1.4\ref{3.1.3} is not balanced: the numbers of each type of atom on the reactant side of the equation (7 carbon atoms, 16 hydrogen atoms, and 2 oxygen atoms) is not the same as the numbers of each type of atom on the product side (1 carbon atom, 2 hydrogen atoms, and 3 oxygen atoms). Consequently, the coefficients of the reactants and products must be adjusted to give the same numbers of atoms of each type on both sides of the equation. Because the identities of the reactants and products are fixed, the equation cannot be balanced by changing the subscripts of the reactants or the products. To do so would change the chemical identity of the species being described, as illustrated in Figure 3.1.33.1.3\PageIndex{3}. Figure 3.1.33.1.3\PageIndex{3}: Balancing Equations. You cannot change subscripts in a chemical formula to balance a chemical equation; you can change only the coefficients. Changing subscripts changes the ratios of atoms in the molecule and the resulting chemical properties. For example, water (H2O) and hydrogen peroxide (H2O2) are chemically distinct substances. H2O2 decomposes to H2O and O2 gas when it comes in contact with the metal platinum, whereas no such reaction occurs between water and platinum. The simplest and most generally useful method for balancing chemical equations is “inspection,” better known as trial and error. The following is an efficient approach to balancing a chemical equation using this method.
    1. Atoms of group 17 gain one electron and form anions with a 1− charge; atoms of group 16 gain two electrons and form ions with a 2− charge, and so on. For example, the neutral bromine atom, with 35 protons and 35 electrons, can gain one electron to provide it with 36 electrons. This results in an anion with 35 protons, 36 electrons, and a 1− charge. It has the same number of electrons as atoms of the next noble gas, krypton, and is symbolized Br−

      Ganham elétrons para preencher os orbitais s e p mais externos

    2. For example, a neutral calcium atom, with 20 protons and 20 electrons, readily loses two electrons. This results in a cation with 20 protons, 18 electrons, and a 2+ charge. It has the same number of electrons as atoms of the preceding noble gas, argon, and is symbolized Ca2

      Loses all valence atoms

    1. Today's society uses fossil fuels as an energy source and the carbon dioxide emission is a concern to many scientists. The following youtube video was created by the EPA to describe the consequences of our economic reliance on fossil fuels

      Why did the EPA remove this educational information? Are they afraid of science?

  5. May 2020
    1. astronomy

      B is the correct answer, Astrology is the study of space and all the physical universe. Astrology falls under one of the Major branches of science. As shown on figure 1.0.1.

    1. monoxide

      Removal of sulfur: Sulfur has to be removed first in a separate process. Magnesium powder is blown through the molten iron and the sulphur reacts with it to form magnesium sulfide. This forms a slag on top of the iron and can be removed. Mg+S→MgS(7) Removal of carbon: The still impure molten iron is mixed with scrap iron (from recycling) and oxygen is blown on to the mixture. The oxygen reacts with the remaining impurities to form various oxides. The carbon forms carbon monoxide. Since this is a gas it removes itself from the iron! This carbon monoxide can be cleaned and used as a fuel gas. Removal of other elements: Elements like phosphorus and silicon react with the oxygen to form acidic oxides. These are removed using quicklime (calcium oxide) which is added to the furnace during the oxygen blow. They react to form compounds such as calcium silicate or calcium phosphate which form a slag on top of the iron.

    1. he atomic weight of chorine is ______________and the atomic number of chlorine-35 is________________. 35, 17 17, 35 35.4527; 17 35.4527; 35 Answer C) the atomic weight is the average of mass of all isotopes of chlorine atoms and found below the symbol on the periodic table. The atomic number is the number of protons in all chlorine atoms and is found on the top of the symbol in the periodic table

      How is the answer C when the periodic table expresses it as Cl 35.453 Chlorine?

    1. An alpha particle is composed of 2 protons and 2 neutrons. It has a charge of 2. The original atoms atomic number decreases by 2 and the mass decreases by 4.

    2. Gamma rays knock out electrons out of atoms and give them a charge.

    3. A beta particle is an electron (former atom in the nucleus) kicked out of the nucleus. It contains a charge of -1.

    4. Alpha particles, beta particles, and gamma rays are the key types of radioactivity.

    1. A battery in the circuit creates a voltage between the plates. Next to the plates is a small disk containing a tiny amount (∼0.0002 g) of the radioactive element americium (Am). The radioactivity of the americium ionizes the air between the plates, causing a tiny current to constantly flow between them.

      The battery in the circuit makes a voltage between the metal plates and near the small disk containing a tiny amount of the radioactive element americium. The radioactivity of the americium ionizes the air between the plates. This causes a tiny current to flow consistantly between them.

    2. Smoke detectors depend on radioactivity.

    1. ms=+1/2

    2. Electrons enter higher-energy subshells only after low-energy subshells have been filled to capacity.

    3. Electron configuration: The # of the principal quantum shell,n; the letter that designates the orbital type; a superscript # that designates the number of the electrons in the particular sub shell.

    4. energy of atomic orbitals increases as the principal quantum number, n, increases.

    5. As described earlier, the periodic table arranges atoms based on increasing atomic number so that elements with the same chemical properties recur periodically. When their electron configurations are added to the table (Figure 3.1.63.1.6\PageIndex{6}), we also see a periodic recurrence of similar electron configurations in the outer shells of these elements.

      Both periodic table and electron configuration have the elements recur periodically so that it is easier to read and understand.

    6. It is important to remember that the periodic table was developed on the basis of the chemical behavior of the elements, well before any idea of their atomic structure was available.

      The periodic table was solely originated on its behavior at first because they have not found out about each element's atomic structure yet.

    7. corresponding family members carbon, nitrogen, oxygen, fluorine, and neon,

      In addition, because of their electrons,these elements are in the same period/row. They also increase electrons as you go down the row.

    8. The electron configurations of silicon (14 electrons), phosphorus (15 electrons), sulfur (16 electrons), chlorine (17 electrons), and argon (18 electrons) are analogous in the electron configurations

      Silicon, phosphorus, sulfur, chlorine, and argon all are similar and comparable in a way because of the electrons in their outer shells.

    9. Since the arrangement of the periodic table is based on the electron configurations,

      Both the periodic table and the electron configurations are related.

    10. The number of the principal quantum shell, n, The letter that designates the orbital type (the subshell, l), and A superscript number that designates the number of electrons in that particular subshell.

      For example, the notation 2p4 (read "two–p–four") indicates four electrons in a p subshell (l = 1) with a principal quantum number (n) of 2

    11. As the principal quantum number, n, increases, the size of the orbital increases and the electrons spend more time farther from the nucleus.

      when not it should increase

    12. The 1s orbital at the bottom of the diagram is the orbital with electrons of lowest energy. The energy increases as we move up to the 2s and then 2p, 3s, and 3p orbitals, showing that the increasing n value has more influence on energy than the increasing l value for small atoms.

      when it's 2s,2p and so more.

    13. lithium with an atomic number of 3.

      It all depends on there atomic number!!!

    1. =

      There is no turbidity. Orange pigmentation at the bottom and top

    2. =

      The sediment at the bottom is slowly growing aggressively making the color turn yellow.

    3. =

      There is no pellicle. The sediment is only at the bottom following turbidity above.

    4. =

      Sediment is at the bottom, above is the turbidity, and the pellicle is laying at the top.

  6. chem.libretexts.org chem.libretexts.org
    1. The first link is to a page on this site and the other one links to wikipedia.  Same goes for the links in the table.

      Possibly not true anymore

    2. an equation

      I should do this now.

    3. My Questions (in here since you said to link to my page anyway):

      These questions have all mostly been answered already.

    1. In Example 10.4.3, the equation is wrong; it should be PiTf = PfTi

      Furthermore, in Example 10.4.6, 0.17L should be changed to 0.157L

      Please check the Annotations for the most up-to-date information.

    2. ρ

      Should be \(M\)

    3. 0.17L

      Should be 0.157L

    4. PiTi=PfTf

      This equation is wrong; it should be TiPf = TfPi

    1. Radioactivity can be expressed in a variety of units, including rems, rads, and curies.

      Radioactive is expressed in units

    2. Many people are aware of nuclear power plants and nuclear bombs, but nuclear chemistry also has applications ranging from smoke detectors to medicine, from the sterilization of food to the analysis of ancient artifacts. In this chapter, we will examine some of the basic concepts of nuclear chemistry and some of the nuclear reactions that are important in our everyday lives.

      The power is combined.

  7. human.libretexts.org human.libretexts.org
    1. weird sisters

      The title "Weird Sisters" indicates a certain connection these characters have with fate, but is also a phrase used to describe those of uncanny or unusual appearance. See our Closer Look "Women, Witchcraft, and Power" for more about witchcraft in this work and society.

    1. When water vapor condenses into rain, that heat is then returned to the oceans.

      Heat returns only to the oceans? Water condenses in the atmosphere.

    1. If α>p-valueα>p-value\alpha > p\text{-value}, reject H0H0H_{0}.

      If p is low, the null must go.

    2. Suppose you make an assumption about a property of the population (this assumption is the null hypothesis). Then you gather sample data randomly. If the sample has properties that would be very unlikely to occur if the assumption is true, then you would conclude that your assumption about the population is probably incorrect.

      Rare Event Rule

    1. Viral Entry into the Host Cell a. Enveloped viruses Enveloped viruses enter the host cell in one of two ways: 1. In some cases, the viral envelope may fuse with the host cell cytoplasmic membrane and the nucleocapsid is released into the cytoplasm (see Figs. 2A, Figure 2B and Figure 2C).

      iral Entry into the Host Cell a. Enveloped viruses

      Enveloped viruses enter the host cell in one of two ways:

      1. In some cases, the viral envelope may fuse with the host cell cytoplasmic membrane and the nucleocapsid is released into the cytoplasm (see Figs. 2A, Figure 2B and Figure 2C).
    1. When the file is read using a for loop in this manner, Python takes care of splitting the data in the file into separate lines using the newline character. Python reads each line through the newline and includes the newline as the last character in the line variable for each iteration of the for loop.

      This is how python reads files in a for loop

    1. elastic

      What is an elastic collision? An elastic collision is a collision in which there is no net loss in kinetic energy in the system as a result of the collision. Both momentum and kinetic energy are conserved quantities in elastic collisions.

      Suppose two similar trolleys are traveling toward each other with equal speed. They collide, bouncing off each other with no loss in speed. This collision is perfectly elastic because no energy has been lost. In reality, examples of perfectly elastic collisions are not part of our everyday experience. Some collisions between atoms in gases are examples of perfectly elastic collisions. However, there are some examples of collisions in mechanics where the energy lost can be negligible. These collisions can be considered elastic, even though they are not perfectly elastic. Collisions of rigid billiard balls or the balls in a Newton's cradle are two such examples.

      What is an inelastic collision? An inelastic collision is a collision in which there is a loss of kinetic energy. While momentum of the system is conserved in an inelastic collision, kinetic energy is not. This is because some kinetic energy had been transferred to something else. Thermal energy, sound energy, and material deformation are likely culprits. Suppose two similar trolleys are traveling towards each other. They collide, but because the trolleys are equipped with magnetic couplers they join together in the collision and become one connected mass. This type of collision is perfectly inelastic because the maximum possible kinetic energy has been lost. This doesn't mean that the final kinetic energy is necessarily zero; momentum must still be conserved. In the real world most collisions are somewhere in between perfectly elastic and perfectly inelastic. A ball dropped from a height hhh above a surface typically bounces back to some height less than hhh, depending on how rigid the ball is. Such collisions are simply called inelastic collisions.

      Are there any examples of perfectly inelastic collisions?

      The ballistic pendulum is a practical device in which an inelastic collision takes place. Until the advent of modern instrumentation, the ballistic pendulum was widely used to measure the speed of projectiles. In this device, a projectile is fired into a suspended heavy wooden block. The wooden block is initially stationary. Following the collision the projectile becomes embedded in the block. Some kinetic energy gets transformed into heat, sound, and used to deform the block. However, momentum must still be conserved. Consequently, the block swings away at some speed. After the collision, the block behaves as a pendulum in which total mechanical energy is conserved.

    1. ideal gas law.
    2. symbol R

      tandard Temperature and Pressure (STP) Standard condition of temperature and pressure is known as STP. Two things you should know about this is listed below. The universal value of STP is 1 atm (pressure) and 0o C. Note that this form specifically stated 0o C degree, not 273 Kelvin, even thought you will have to convert into Kelvin when plugging this value into the Ideal Gas equation or any of the simple gas equations. In STP, 1 mole of gas will take up 22.4 L of the volume of the container.

  8. Apr 2020
    1. electron affinity is the ability of an atom to accept an electron

      This is the ability in which an atom is able to accept an electron from somewhere else.

    2. The first ionization energy is the energy requiredto remove the outermost, or highest, energy electron, the second ionization energy is the energy required to remove any subsequent high-energy electron from a gaseous cation, etc.

      This explains how many elements could have more than 1 ionization energy.

    3. However, the most common scale for quantifying electronegativity is the Pauling scale (Table A2), named after the chemist Linus Pauling

      Though there can be more, the most common scale for quantifying electronegativity is through the Pauling scale. This scale was named after Linus Pauling.

    4. Periodic trends are specific patterns that are present in the periodic table that illustrate different aspects of a certain element, including its size and its electronic properties

      The periodic table contains specific patterns that can occur in the elements which often gives us the electronegativity, ionization energy, electron affinity, and atomic radius.

    5. Rewrite the following list in order of decreasing electron affinity: fluorine (F), phosphorous (P), sulfur (S), boron (B).

      F, S, P, B

    6. Why is the electronegativity value of most noble gases zero?

      Noble gases already have a full valence electron shell so they do not need to lose or gain valance electrons.

    7. Arrange these atoms in order of decreasing effective nuclear charge by the valence electrons: Si, Al, Mg, S

      Si, S, Al, Mg

    8. electron affinity is the ability of an atom to accept an electron

      The ability to to take electrons.

    9. Electron shielding describes the ability of an atom's inner electrons to shield its positively-charged nucleus from its valence electrons.

      Electrons that are in inner levels try to push away other electrons.

    10. Ionization energy is the energy required to remove an electron from a neutral atom in its gaseous phase.

      It's the opposite of electronegativity.The ability to take an electron.

    11. The nature of electronegativity is effectively described thus: the more inclined an atom is to gain electrons, the more likely that atom will pull electrons toward itself.

      Elements will try to gain an octet the most effective way possible.

    12. Electronegativity

      The ablility to attract and confine an electron.

    13. Periodic trends

      Periodic trends define the characteristics of atoms.

    14. Generally, the stronger the bond between the atoms of an element, the more energy required to break that bond.

      This makes sense and it would be vice versa for weak bond between the atoms of an element, the less energy required to break that bond.

    15. The atomic radius is one-half the distance between the nuclei of two atoms (just like a radius is half the diameter of a circle).

      When I read this It brought me back to when I was taught about the radius of a circle and diameter in math class.

    16. Ionization energy is the energy required to remove an electron from a neutral atom in its gaseous phase. Conceptually, ionization energy is the opposite of electronegativity.

      The energy is required to move electrons

    17. The first ionization energy is the energy requiredto remove the outermost, or highest, energy electron, the second ionization energy is the energy required to remove any subsequent high-energy electron from a gaseous cation, etc.

      Good thing to note that some elements could have several ionization energies.

    18. The lower this energy is, the more readily the atom becomes a cation. Therefore, the higher this energy is, the more unlikely it is the atom becomes a cation.

      I realized that cation means to become a more positive charged ion.

    19. The lanthanides and actinides possess more complicated chemistry that does not generally follow any trends.

      No wonder they dont follow any general trends their more complex then Noble gases.

    20. Because elements on the left side of the periodic table have less than a half-full valence shell, the energy required to gain electrons is significantly higher compared with the energy required to lose electrons. As a result, the elements on the left side of the periodic table generally lose electrons when forming bonds.

      On the periodic table from left to right the electronegativity increases.

    21. However, the most common scale for quantifying electronegativity is the Pauling scale (Table A2), named after the chemist Linus Pauling.

      This was interesting to realized Pauling scale was named after Linus Pauling. Also, how electronegativity describes an atoms ability to attract and bin with other electrons.

    22. Periodic trends are specific patterns that are present in the periodic table that illustrate different aspects of a certain element, including its size and its electronic properties.

      The periodic table has different patterns involved such as electronegativity, ionization energy, electron affinity, atomic radius, the types of groups, and more.

    23. Periodic trends are specific patterns that are present in the periodic table that illustrate different aspects of a certain element, including its size and its electronic properties. Major periodic trends include: electronegativity, ionization energy, electron affinity, atomic radius, melting point, and metallic character. Periodic trends, arising from the arrangement of the periodic table, provide chemists with an invaluable tool to quickly predict an element's properties. These trends exist because of the similar atomic structure of the elements within their respective group families or periods, and because of the periodic nature of the elements.

      A periodic table contains patterns that occur in elements, giving us the electronegativity, ionization energy, electron affinity, atomic radius, etc.

    1. Marriage

      Sociologists define marriage as a socially supported union involving two or more individuals in what is regarded as a stable, enduring arrangement typically based at least in part on a sexual bond of some kind.Nov 1, 2019