Water ionizes by the equation H2O(l)H+(aq)+OH(aq) The extent of the reaction is

Question

Water ionizes by the equation

H2O(l)H+(aq)+OH(aq)

The extent of the reaction is small in pure water and dilute aqueous solutions. This reaction creates the following relationship between [H+] and [OH]:

Kw=[H+][OH]

Keep in mind that, like all equilibrium constants, the value of Kw changes with temperature.

A)

What is the H+ concentration for an aqueous solution with pOH = 3.51 at 25 C?

Express your answer to two significant figures and include the appropriate units.

B) At a certain temperature, the pH of a neutral solution is 7.56. What is the value of Kw at that temperature?

Express your answer numerically using two significant figures.

Explanation / Answer

A)

What is the H+ concentration for an aqueous solution with pOH = 3.51 at 25 C?

pOH = 3.51 = -log[OH-]

so log [OH-] = -3.51

[OH-] = 3.09 X 10^-4

so [H+] = 10^-14 / 3.09 X 10^-4 = 3.23 X 10^-11

B) If pH of neutral solution = 7.56

For neutral solutions [H+] = [OH-]

Now pH = -log[H+] = 7.56

so log[H+] = -7..56

[H+] = 2.75 X 10^-8

so [OH-] = 2.75 X 10^-8

So Kw = [H+]X[OH-] = 2.75 X 10^-8 X 2.75 X 10^-8 = 7.56 x 0^-16

B) At a certain temperature, the pH of a neutral solution is 7.56. What is the value of Kw at that temperature?

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