Question

I. The pH of 1M NaOH is 13.
II. ${\text{pH + pOH = 14}}$.

a.) Statement I is true, Statement II is true and is a correct explanation of the phenomena described in I.
b.) Statement I is true; Statement II is false.
c.) Statement I is false; Statement II is true.
d.) Statement I is false; Statement II is false.

Answer 1

Hint: Knowing the pH of a compound, gives us an idea about whether the compound is acidic or basic. We should first know whether the statement I mentioned is correct or not. And then accordingly move to statement II.



Complete step by step solution: Examining statement I we get that,
Let us assume that 0.1 M of NaOH is a strong base, so this will produce 0.1mol/L of OH ions in solution.
Therefore,
$\eqalign{
  & {\text{pOH = }} - \log \left[ {1 \times {{10}^{ - 1}}} \right] \cr
  & = {\text{ }} - \log \left[ 1 \right]{\text{ + }} - \log \left[ {{{10}^{ - 1}}} \right] \cr
  & = {\text{ 0 + 1 }} \times {\text{ 1}} \cr
  & {\text{ = 0 + 1}} \cr
  & {\text{ = 1}} \cr} $
Now we know that,
$\eqalign{
  & {\text{pH + pOH = 14}} \cr
  & {\text{pH + 1 = 14}} \cr
  & {\text{pH = 14 }} - {\text{ 1}} \cr
  & {\text{pH = 13 }} \cr} $
Therefore, the pH of 0.1 M NaOH solution is 13.
So, we can say that statement I is true, and statement II is true and is the correct explanation of the phenomena described in I.
Therefore, the correct answer to the question is Option A.
Additional Information: pH can also be defined as equal to the negative log base 10 of the concentration of protons in the solution.



Note: pOH is defined as the measure of the hydroxide ion or ${\text{O}}{{\text{H}}^ - }$ concentration. It is used to express the alkalinity of a solution.
High pH means the solution is basic in nature. High pOH means the solution is acidic in nature.