The ionization constant of water at a temperature above 25°C is 3.5 × 10^-14.What is the pH of pure water at this temperature?
2H₂O(l)
H₃O⁺(aq) + OH^-(aq)

Question

The ionization constant of water at a temperature above 25°C is 3.5 × 10^-14.What is the pH of pure water at this temperature? 2H₂O(l) H₃O⁺(aq)+ OH^-(aq) A)7.73 B)5.53 C)6.73 D)13.49 E)7.00

Quizplus · Accepted Answer

At 25°C, the ionization constant of water, Kw, is 1.0 × 10^-14. However, at a higher temperature, Kw increases as water becomes a better conductor of electricity.

Using the formula pH = -log[H+], we can find the pH of pure water by first finding the concentration of H+ ions in pure water. Since pure water is neutral, the concentration of H+ ions is equal to the concentration of OH- ions, and can be found as follows:

Kw = [H+][OH-]
3.5 × 10^-14 = [H+][OH-]

Taking the square root of both sides gives:

[H+] = [OH-] = √(3.5 × 10^-14) ≈ 1.87 × 10^-7 M

Now we can find the pH of pure water as:

pH = -log(1.87 × 10^-7) ≈ 6.73

Therefore, the best choice is C.

The Ionization Constant of Water at a Temperature Above 25°C