Question

Which statement is true for a solution when its concentration of hydroxide ions increases? It becomes more acidic. It becomes less alkaline. Its pH value increases. Its pH value decreases.

Answer 1

Answer: Option (c) is the correct answer.

Explanation:

When we increase the concentration of a substance then it means we are increasing number of molecules of the substance. So, when there is increase in concentration of hydroxide ions the it means there are more number of $OH^{-}$ ions into the solution.

Also, it is known that pOH = $log \frac{1}{OH^{-}}$

Since there is increase in $[OH^{-}]$ concentration so, this means that there will be decrease in the value of pOH.

Also,   pH + pOH = 14

so,                pH = 14 - pOH

                    pH = +ve

Thus, we can conclude that there will be increase in the value of pH.

Answer 2

Answer:

Its pH value increases.

Explanation:

pH is the measure of alkalinity or acidity of a compound.

pH = - log [H+]

and pH + pOH = 14

where pOH is the measure of basicity of a solution, given by -log[OH-]

As a solution gets more basic that is higher [OH-], the pH increases, and on the other hand, as the pH of a solution decreases by one pH unit, the concentration of H+ increases by ten times.