Question

What is the quantity of NaOH present in $250$ cc of the solution, so that it gives a pH$=13$?

• A. ${10}^{-13}$ g
• B. ${10}^{-1}$ g
• C. $1.0$ g
• D. $4.0$g

Answer 1

Answer: (C)

$1.0$ g

If $pH$ $=13$, the $pOH$ $=14-13=1$

If $pOH$ $=1,\left[O{H}^{-}\right]={10}^{-}$ $pOH$ $=0.10$

Since $NaOH=0.10M$,then:

$0.10mol/L\times 0.250L=0.025molNaOH$

Mass of $NaOH=0.025mol\times 40g/mol=1gNaOH$.