Answer
The mass percent of this solution is equal to 17.0% (m/m) $Na_2SO_4$
Work Step by Step
1. Write the expression for the mass percent:
$$Mass \space percent(m/m) = \frac{grams \space of \space solute}{grams \space of \space solution} \times 100\%$$
Mass of solution = Mass of solute + Mass of solvent
$$Mass \space percent(m/m) = \frac{ 15.5 \space g \space Na_2SO_4 }{( 15.5 \space g + 75.5 \space g) \space solution} \times 100\%$$
Mass percent(m/m) = $17. 0\%$ (m/m) $Na_2SO_4$ solution
