What is the normal pH of human blood?

Which equation represents the $pH$ of a solution?

When sodium chloride is dissolved in water,the sodium ion undergoes ........

There are two different solutions, $A$ and $B$. The $pH$ of solution $A$ is $4$. Find the $pH$ of solution $B$ having $[H^+]$ concentration three times that of solution $A$.

If $[H_3O^{+}] = 3.5 \times 10^{-8} \ M$,calculate $[OH^{-}]$ and $pH$ of the solution.

The $pH$ of a solution is $9.5$. The solution is