pH of acids, bases and salts

Exercise 17

    

Calculate the mass of sodium hydroxide that must be dissolved in a volumetric flask $J$ of 250 $mL$ in order to obtain a solution with $pH$ = 13.18.

$NaOH$: strong base Final solution: $pH$ $=$ $14$ $+$ $log\;[OH^-]$ $[OH^-]$ $=$ $10^{pH-14}$ = 0.15 $\frac{mol}{L}$ $c_{NaOH}$ $=$ $\frac{0.15}{1}$ $n_{NaOH}$ = $c_{NaOH}\cdot V_{J}$ = 0.15$\cdot$0.25 = 0.0375 $\;mol$ $m_{NaOH}$ = $n_{NaOH}\cdot M_{NaOH}$ = 0.0375$\cdot$40.01 = 1.5$\; g$