We’re being asked to calculate the mass percent when 18.9 g solid is dissolved in 39.5 g water.

We’re given the mass percent of the solution and we're going to use the **mass percent formula** shown below:

$\overline{){\mathbf{mass}}{\mathbf{}}{\mathbf{percent}}{\mathbf{=}}\frac{\mathbf{mass}\mathbf{}\mathbf{component}}{\mathbf{total}\mathbf{}\mathbf{mass}}{\mathbf{\times}}{\mathbf{100}}}$

Since we are dealing with a **solution**, we can rewrite the equation as:

$\overline{){\mathbf{\%}}{\mathbf{}}{\mathbf{mass}}{\mathbf{=}}\frac{\mathbf{mass}\mathbf{}\mathbf{solute}}{\mathbf{mass}\mathbf{}\mathbf{solution}}{\mathbf{\times}}{\mathbf{100}}}$

**Calculate the mass of mass percent solid****:**

What is the mass percent of a solution prepared by dissolving 18.9 grams of solid into 39.5 grams of water?

A) 47.8%

B) 58.4%

C) 32.4%

D) The identity of the compound must be known.

E) none of the above