What is percent concentration?

1 Answer
Ernest Z.
Aug 20, 2014

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 = mass of solutetotal mass of solution × 100 %

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 =

mass of glucosetotal mass of solution×100%=26.5g500g × 100 % = 5.30 %

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 = volume of solutetotal volume of solution × 100 %

Example

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

Solution

70 % = volume of rubbing alcoholtotal volume of solution×100% × 100 %

So

Volume of rubbing alcohol = volume of solution × 70 %100 % = 250 mL × 70100

= 175 mL

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

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