C3 - Concentration Of Solutions

What does concentration of a solution mean?

The amount of solute dissolved in a given volume of solution.

What is a solute?

A chemical that is dissolved in a solvent.

What is a solvent?

The liquid that dissolves the solute (often water).

What are the units for concentration of a solution?

Grams per decimetre cubed (g/dm³).

How many cm³ are in 1 dm³?

1000 cm³.

What is the equation for concentration in g/dm³?

Concentration = Mass of solute ÷ Volume of solution.

How do you calculate mass of solute if given concentration and volume?

Mass = Concentration × Volume.

How do you calculate volume of solution if given mass and concentration?

Volume = Mass ÷ Concentration.

Example: 200 g of chemical in 1 dm³ solution. What is the concentration?

200 ÷ 1 = 200 g/dm³.

Example: 150 g of chemical in 0.5 dm³ solution. What is the concentration?

150 ÷ 0.5 = 300 g/dm³.

Example: What mass of solute is needed to make 0.4 dm³ of solution with concentration 600 g/dm³?

600 × 0.4 = 240 g.

Example: 200 g of chemical forms a solution of concentration 800 g/dm³. What is the volume?

200 ÷ 800 = 0.25 dm³.

(Higher) What happens to concentration if mass of solute increases but volume stays the same?

Concentration increases.

(Higher) What happens to concentration if volume increases but mass of solute stays the same?

Concentration decreases.

Exam tip: What should you always check when using the concentration formula?

Make sure volume is in dm³, not cm³.