Question

As the temperature increases, the pH of the KOH solution
A.Will decrease
B.Will increase
C.Remains constant
D.Depends upon the concentration of KOH solution.

Answer 1

The pH of a solution is the negative logarithm to the base 10 of the hydronium ion concentration of a solution and there are many factors that affect the release of the hydronium ions in the medium. Increase in temperature increases the dissociation value of the acid or base.

Complete stepwise solution:
There are different factors affecting the pH of the medium as it is a measure of the ${{\text{H}}^{\text{ + }}}$ions released in the medium and the release of the ${{\text{H}}^{\text{ + }}}$ions is affected by the temperature of the medium, the presence of other cations and anions, presence of catalysts, and the pressure of the medium.
pH of the medium is temperature dependent because the release of ${{\text{H}}^{\text{ + }}}$ions in a medium is dependent on the temperature of the medium. But for ionic compounds such as ${\text{KOH}}$ the rate of reaction is unaffected by temperature because these compounds dissociate completely in water to form cations and anions and are not reversible in nature.
${\text{KOH}} \to {{\text{K}}^{\text{ + }}}{\text{ + O}}{{\text{H}}^{\text{ - }}}$
So the increase or decrease of temperature will not affect the pH of the solution of KOH.

Hence, option C is the correct option.

Notes:
1.The pH of covalent compounds such as water are affected by temperature because their dissociation is a reversible reaction.
2.Reversible reactions are guided by Le-Chatelier’s principle according to which any change in a dynamic equilibrium is undone by the system.
3.The dissociation of water being an endothermic reaction, whenever the temperature is increased the rate of forward reaction increases while a decrease in temperature increases the rate of backward reaction.