Question

A solution having an equal number of H+ ions and OH- ions will have a pH of
A.3
B.7
C.9
D.11

Answer 1

In this case, the solution is neutral, being neither acidic or basic.

By definition this happens when the concentration of H ions is \( a_{H+} = 10^{-7} \)moles/liter. Thus by definition of pH,
\[ pH = \log_{10}(1/a_{H+}) = 7 \]

Answer 2

7 because it is natural