Pure water is ionised according to the equation: 2H2O(l) −⇀↽−\ce{ } H3O+(aq) + OH−(aq) Kw = 10-14 and ΔH = + 57.2 kJ mol-1 As the temperature of pure water is increased, its pH would be expected to

Question

Pure water is ionised according to the equation: 2H2O(l) −⇀↽−\ce{ <=> }  H3O+(aq) +  OH−(aq) Kw = 10-14 and ΔH = + 57.2 kJ mol-1 As the temperature of pure water is increased, its pH would be expected to

BlackTom AI · Accepted Answer

The question concerns how the pH of pure water changes with increasing temperature, given the autoionization: 2 H2O ⇌ H3O+ + OH− with Kw = [H3O+][OH−]. The key concept is that the autoionization of water is endothermic (ΔH > 0). For endothermic equilibria, increasing temperature shifts the equilibrium to the right, increasing Kw. In pure water, [H3O+] = [OH−], so pH = −log[H3O+]. If Kw increases, [H3O+] increases as the square root of Kw (since [H3O+] = [OH−] = sqrt(Kw)), which makes pH = −log(sqrt(Kw)) decrease as Kw grows.

To address potential options (even though the option list is not provided here):
- If an option stated that pH increases with temperature, that would be incorrect because increasing Kw raises [H3O+] and thus lowers pH in pure water.
- If an option claimed pH remains unchanged, that would be incorrect because Kw changes with temperature for water, altering [H3O+].
- If an option suggested pH becomes more acidic (i.e., decreases) as temperature rises, that aligns with the thermodynamic reasoning for an endothermic dissolution whose equilibrium constant Kw increases with temperature.

In summary, as temperature increases, Kw increases for pure water due to the endothermic nature of water autoionization, leading to a higher concentration of hydronium ions and a lower pH. The correct behavioral statement is that the pH decreases with increasing temperature, reflecting greater autoionization and higher [H3O+] in pure water.

MUF0041 Chemistry Unit 1 - Semester 1, 2025 Area of Study 3 Test 3 (Acids and Bases)

Pure water is ionised according to the equation: 2H2O(l) −⇀↽−\ce{ <=> } H3O+(aq) + OH−(aq) Kw = 10-14 and ΔH = + 57.2 kJ mol-1 As the temperature of pure water is increased, its pH would be expected to

查看解析

登录即可查看完整答案

类似问题

Question at position 16 Which statement is false? Which statement is false? Cold water has a lower pH than hot waterKw = [OH—][H+]Water dissociation is endothermicAs T increases, Kw increases Clear my selection

In a consumer society, many adults channel creativity into buying things

Economic stress and unpredictable times have resulted in a booming industry for self-help products

People born without creativity never can develop it

A product has a selling price of $20, a contribution margin ratio of 40% and fixed cost of $120,000. To make a profit of $30,000. The number of units that must be sold is: Type the number without $ and a comma. Eg: 20000

Which of the following statement regarding cost is correct:

Under the assumptions used in cost-volume-profit analysis, as the activity increases:

更多留学生实用工具

考试浏览器助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单