self-ionization of water

[00945584]

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Given that the self-ionization of water is endothermic, what is the value of the sum pH + pOH at 50C.

H2O(l) + H2O(l) ----> H3O+ (aq) + OH- (aq)

a. LESS THAN 14
B. EQUAL TO 14
C. GREATER THAN 14
D. CAN'T DETERMINE.

HOW IS THE ANSWER A.

 

[loveoforganic]

Decreasing pH indicates increasing acidity, just like decreasing pOH indicates increasing basicity. So, you bumped temperature up in an endothermic reaction, and the reaction shifts toward the products. Your normal pH of 7 and pOH of 7 both decrease to, say, 6.9. So you now have pH + pOH = 13.8

 

[bjb305]

Given that the self-ionization of water is endothermic, what is the value of the sum pH + pOH at 50C.

H2O(l) + H2O(l) ----> H3O+ (aq) + OH- (aq)

a. LESS THAN 14
B. EQUAL TO 14
C. GREATER THAN 14
D. CAN'T DETERMINE.

HOW IS THE ANSWER A.

The pH scale from 1-14 is based on this reaction of water having 10^-7 concentration of H in solution at 25 celsius. Since you increased the temp, you're going to drive the reaction to the right, giving more H and OH ions in solution. So now let's say you have 10^-5 of both. Now even tho your new pH is 5, it is still a neutral solution because the pH + pOH is 10. make sense?