a) Is the process of KNO3 dissolving in water spontaneous at all temperatures st
ID: 966197 • Letter: A
Question
a) Is the process of KNO3 dissolving in water spontaneous at all temperatures studied? Briefly explain.
b) Is the reaction in (a) one that gives off heat or requires heat? Briefly explain.
c)Is your value of delta S consistent with the expected change in disorder for the reaction in Equation 1? Brieflt explain.
d) A few compounds exist whose solubility decreases as the tempurature increases. How would the values for delta G, delta H, and delta S for these reactions be different from those values aobserved for the solubility of KNO3? Briefly explain.
Explanation / Answer
a) For a reaction to be spontaneous the delta G value must be negative. Delta G is given by
dG = dH - TdS
Since dissolution of KNO3 in water disassociates into free ions, the entropy of the process increases and since the process is endothermic delta G remains negative at all temperatures.
So KNO3 dissolving in water is spontaneous at all temperatures.
b) KNO3 when dissolved in water gives K+ and NO3- ions. Since bond is broken in the process energy is required to break the bond for which energy should be absorbed. So dissolving KNO3 in water is endothermic process
c) Well as i have mentioned in the first part of the answer, the entropy of the system increases which makes dS positive for all temperatures. Sometimes however delta S is negative because there is a large loos of entropy in the hydration of the ions.
d) delta G = -RTlnKeq = deltaH - T deltaS
Usually delta S is positive breaking up of the regular crystal lattice so -TdeltaS becomes more negative with increasing T and compound is more soluble in hot water
Sometimes however delta S is negative because there is a large loos of entropy in the hydration of the ions. This effect is most noticable in the +2 charge ions where one is large anion and other is small cation. So these compounds become less soluble in hot water. But for some compounds solubilities increase and decrease with temperature like CdSO4.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.