Question

9. Which of the following is false?

As [H*] increases, the pH decreases.
As the [H*] increases, the [OH'] decreases.
If the pH of a solution is 2, the [OH] ion concentration is 10-12.
If the pH of a solution is 5, the [OH] ion concentration is 10-5.

Answer 1

The false statement among the given options is:

"If the pH of a solution is 2, the [OH] ion concentration is 10-12."

The pH and the [OH-] ion concentration are related through the equation:

pH + pOH = 14

where pOH = -log[OH-] and pH = -log[H+].

If the pH of a solution is 2, then pOH can be calculated as:

pOH = 14 - pH = 14 - 2 = 12

Then, [OH-] can be obtained by taking the antilog of -12:

[OH-] = 10^(-pOH) = 10^(-12) = 1 × 10^(-12) = 0.000000000001 or 1 nanomolar (nM)

So, the correct statement is: If the pH of a solution is 2, the [OH] ion concentration is 10-12. (This statement is false.)