Question

What are percentages of concentration?

Answer 1

There are three common percentages of concentration: mass percent, volume percent, and mass per volume percent.

Percent means "per hundred".

Mass Percent (m/m)

Mass percent is the number of grams of substance in 100 g of the mixture. The formula is

Mass % = `("mass of substance")/("mass of mixture")` × 100 %

Volume Percent (m/v)

Volume percent is the number of millilitres of substance in 100 mL of the solution. The formula is

Volume % = `("volume of substance")/("volume of solution")` × 100 %

Mass by Volume Percent (m/v)

Mass by volume percent is the number of grams of substance in 100 mL of the solution. The formula is

m/v % = `("mass of substance")/("volume of mixture")` × 100 %

Examples

1. Calculate the mass percent of NaCl in a solution that contains 300 g NaCl in 1200 g solution.

2. Calculate the volume percent of isopropyl alcohol in a solution that contains 700 mL of isopropyl alcohol in 1.00 L of solution.

3. Calculate the m/v % of K₂SO₄ in a solution that contains 75.0 g K₂SO₄ in 1.50 L of solution.

Solutions

1. m/m % NaCl = `("mass of NaCl")/("mass of solution")` × 100 % = `(300"g")/(1200"g")` × 100 % = 25.0 %

2. v/v % = `("volume of isopropyl alcohol")/("volume of solution")` × 100 % = `(700"mL")/(1000"mL")` × 100 % = 70.0 %

3. m/v % = `("mass of K₂SO₄")/("volume of solution")` × 100 % = `(75.0"g")/(1500"mL")` × 100 % = 5.00 %