For liquid chemicals (such as oils and other organic liquids), volume may be more convenient to measure than mass. Percent by volume (or volume percent, vol%, (%v/v), etc) is often used to report concentration for these mixtures:

$$\text{% v/v}=\frac{\text{volume of solute}}{\text{volume of solution}} \times 100\%$$

As with mass percent, remember that the denominator is the volume of the **entire solution**, not just the solvent (and in many cases, the total volume is not equal to the sum of the two liquids being mixed!)

#### Calculations using Volume Percentage

Rubbing alcohol (isopropanol) is usually sold as a 70%v/v aqueous solution. If the density of isopropyl alcohol is 0.785 g/mL, how many grams of isopropyl alcohol are present in a 355 mL bottle of rubbing alcohol?

#### Solution

Per the definition of volume percentage, the isopropanol volume is 70% of the total solution volume. Multiplying the isopropanol volume by its density yields the requested mass: $$(355\,mL\;\text{solution})\left(\frac{70\,mL\;\text{isopropyl alcohol}}{100\,mL\;\text{solution}}\right) \left(\frac{0.785\,g\;\text{isopropyl alcohol}}{1\,mL\;\text{isopropyl alcohol}}\right)\\ =\,195\,g\;\text{isopropyl alcohol}$$