Question

The number of ${OH}^{-}$ ions in one mL solution of $pH=3$ is:

• A. $6.023\times {10}^6$
• B. $6.023\times {10}^{10}$
• C. $6.023\times {10}^9$
• D. none of the above

Answer 1

Answer: (C)

$6.023\times {10}^9$

Given, pH$=3$

pOH $=14-pH=14-3=11$

$-log\left[O{H}^{-}\right]=11$

$\left[O{H}^{-}\right]={10}^{-11}M$

Therefore, the number of ions in $1$ ml is ${10}^{-11}\times {10}^{-3}\times N_A=6.023\times {10}^9$.