A $2.90 g$ mixture of $NaOH$ and $Ca (OH) X_{2}$ (molar masses $40$ and $74 g mo l^{- 1}$ ) is exactly neutralised by $75.5 mL$ of $1.00 N$ $HCl$ . Calculate the mass percentage of $NaOH$ in the mixture (one decimal place).

Numerical answer type, answer in %, tolerance 0.2.

Answer: 49 %

Equivalents of base

= 1.00 \times 0.0755 = 0.0755

. Let

x

g be

NaOH

(

n = 1

, eq. mass

40

) and

(2.90 - x)

g be

Ca (OH) X_{2}

(

n = 2

, eq. mass

37

x /40 + (2.90 - x) /37 = 0.0755

. Hence

x = 1.420 g

. Mass percentage of

NaOH = 49.0%