# What is percent concentration?

##### 1 Answer

There are two types of percent concentration: percent by mass and percent by volume.

**PERCENT BY MASS**

Percent by mass (m/m) is the mass of solute divided by the total mass of the solution, multiplied by 100 %.

Percent by mass =

**Example**

What is the percent by mass of a solution that contains 26.5 g of glucose in 500 g of solution?

*Solution*

Percent by mass =

**PERCENT BY VOLUME**

Percent by volume (v/v) is the volume of solute divided by the total volume of the solution, multiplied by 100 %.

Percent by volume =

**Example**

How would you prepare 250 mL of 70 % (v/v) of rubbing alcohol

*Solution*

70 % =

So

Volume of rubbing alcohol = volume of solution ×

= 175 mL

You would add enough water to 175 mL of rubbing alcohol to make a total of 250 mL of solution.