Now consider the same process in reverse. Suppose that a hot frying pan in a sink of cold water were to become hotter while the water became cooler. As long as the same amount of thermal energy was gained by the frying pan and lost by the water, the first law of thermodynamics would be satisfied

ocesses have a natural tendency to occur in one direction under a given set of conditions. Water will naturally flow downhill, but uphill flow requires outside intervention such as the use of a pump. A spontaneous process is one that occurs naturally under certain conditions. A nonspontaneous process, on the other hand, will not take place unless it is “driven” by the continual input of energy from an external source. A process that is spontaneous in one direction under a particular set of conditions is nonspontaneous in the reverse direction

7.36×10−4 g146.1 g/mol

Ksp=[Ca2+]3[PO3−4]22.07×10−331.92×10−351.14×10−7 M=(3x)3(2x)2=108x5=x5=x(4.5.4)(4.5.5)(4.5.6)(4.5.7)(4.5.4)Ksp=[Ca2+]3[PO43−]2=(3x)3(2x)2(4.5.5)2.07×10−33=108x5(4.5.6)1.92×10−35=x5(4.5.7)1.14×10−7 M=x\begin{align}K_{\textrm{sp}}=[\mathrm{Ca^{2+}}]^3[\mathrm{PO_4^{3-}}]^2&=(3x)^3(2x)^2 \\2.07\times10^{-33}&=108x^5 \\1.92\times10^{-35}&=x^5 \\1.14\times10^{-7}\textrm{ M}&=x\end{align}

: Le Châtelier’s Principle- How a System at Equilibrium Responds to Disturbances