# A solution is made by dissolving 4.87 g of potassium nitrate to a final volume of 86.4 mL solution. What is the weight/volume of the solute?

So given the standard density of water, the mass of the solution is simply, $\left(4.87 + 86.4\right) \cdot g$. For the solution $\text{mass"/"volume"="density} \left(\rho\right)$ $=$ $\frac{\left(4.87 + 86.4\right) \cdot g}{86.4 \cdot m L}$, slightly over $1 \cdot g \cdot m L$. Because nitrate salts are soluble stuff, you could get significantly higher solution densities if you dissolved more salt (volume change would be fairly negligible).