Solution Found!
Like any equilibrium constant,Kw changes with temperature.
Chapter 18, Problem 24P(choose chapter or problem)
Problem 24P
Like any equilibrium constant,Kw changes with temperature. (a) Given that autoionization is endothermic, how does Kw change with rising T? Explain with a reaction that includes heat as reactant or product, (b) In many medical applications, the value of Kw at 37°C (body temperature) may be more appropriate than the value at 25°C, 1.0×10-14. The pH of pure water at 37°C is 6.80. Calculate Kw, pOH, and [OH?] at this temperature.
Questions & Answers
QUESTION:
Problem 24P
Like any equilibrium constant,Kw changes with temperature. (a) Given that autoionization is endothermic, how does Kw change with rising T? Explain with a reaction that includes heat as reactant or product, (b) In many medical applications, the value of Kw at 37°C (body temperature) may be more appropriate than the value at 25°C, 1.0×10-14. The pH of pure water at 37°C is 6.80. Calculate Kw, pOH, and [OH?] at this temperature.
ANSWER:
Solution 24P
Here we have to answer the following questions.
Step 1
(a) Here we have to find out how does Kw change with rising T and have to explain with a reaction that includes heat as reactant or product.
Heat is absorbed in an endothermic process. In this question it has been given that autoionization is an endothermic process. Thus the reaction for absorption of heat by water molecule i.e autoionization of water is given below,
2H2O (l) + heat → H3O+ (aq) + OH- (aq)
Kw = [H3O+ ][OH-]
As the temperature increases, heat added to water molecule and the reaction shifts to the forward direction to form the product.
Thus increase in temperature will increase the value of Kw.