Question

1. if a solution has equal numbers of hydronium and hydroxide ions, what is its ph? a. 0 b. 3.5 c. 7 d. 14

Explanation:

Step1: Recall pH - pOH relationship

In any aqueous solution, $pH + pOH=14$. When the number of hydronium ions $[H_3O^+]$ is equal to the number of hydroxide ions $[OH^-]$, the solution is neutral.

Step2: Determine pOH and pH for neutral solution

For a neutral solution, $[H_3O^+]=[OH^-]=1\times 10^{- 7}\text{ M}$. The pH is defined as $pH =-\log[H_3O^+]$ and pOH is defined as $pOH=-\log[OH^-]$. Since $[H_3O^+]=[OH^-]=1\times 10^{-7}\text{ M}$, then $pH = 7$ and $pOH = 7$.

Answer:

C. 7