Question

The pH of a neutral water is 6.5. Then the temperature of water:
A. Is ${25^ \circ }C$
B. Is more than ${25^ \circ }C$
C. Is less than ${25^ \circ }C$
D. Can be more or less than ${25^ \circ }C$
E. Cannot be predicted

Answer 1

Hint: We have to know that there could decrease in pH with increase in temperature. We should understand that this increase in temperature, decrease in pH does not turn the water highly acidic at high temperatures. In the case of water which is pure, the concentration of hydrogen ions as well as hydroxide ions, the pH of the water would be neutral though there would change in pH.

Complete step by step answer:
We have to know that there would be an increase in ionization with increase in temperature. Hence, the number of active ${H^ + }$ present in the solution would rise with respect to temperature, therefore there could be reduction in pH. If there is reduction in pH of the water which is neutrally, it is generally considered that there could be an increase in temperature from room temperature which is usually ${25^ \circ }C$. Hence, the temperature must be higher than ${25^ \circ }C$ if the pH of neutral water is 6.5. We can say that pH is less than seven, the concentration of hydrogen ion is larger than ${10^{ - 7}}$, if the temperature is higher than ${25^ \circ }C$.

So, the correct answer is Option B .

Note: We must remember that the characteristic of water and phase of water is determined by two factors namely temperature and pressure. In other ways, we know that normal pH of water is seven as it is neutral, hence for pH 6.5 being a little acidic to neutralize it. So, temperature should be increased in order to recompense that neutrality. A solution would be acidic even if there is more concentration of ions of hydrogen over ions of hydroxide.