Answer
The percent by mass in each example is:
(a)
$$ 8.47 \% $$
(b)
$$ 17.7 \% $$
(c) $$ 11 \% $$
Work Step by Step
(a) 1. Calculate the percent by mass:
$$\frac{ 5.75 g \space NaBr }{ 67.9 g \ solution} \times 100\% = 8.47 \% $$
(b)
$$\frac{ 24.6 g \space KCl }{ 24.6 g + 114 g} \times 100\% = 17.7 \% $$
(c) $$\frac{ 4.8 g \space toluene }{ 4.8 g + 39 g} \times 100\% = 11 \% $$
