Concentration of an aqueous solution is the mass of solute dissolved in 1 dm³ of distilled water, in g/dm³.
The mass of one mole of solute is equal to the relative mass of the solute measured in grams.
Concentration can be expressed in g/dm³ or mol/dm³.
Equal volumes of solutions of the same concentration (in mol/dm³) have equal numbers of dissolved solute particles.
Volume can be measured in various units; 1 dm³ is equivalent to 1000 cm³.

Common misconception

Pupils often confuse the chemical definitions for 'concentration' and 'strength'.

Stress that concentration is a measure of particles interspersed throughout a specific volume of liquid.

Keywords

Solution - Substance formed when a solute dissolves into a solvent.
Solute - A substance that has dissolved into a solvent.
Concentration - The amount of a solute dissolved in a certain volume of solvent.
Dilute - A low concentration of a solute in a solution.
Moles - 6.02 × 10²³ of something. The mass of a mole of a substance is its relative mass expressed in grams.

Use a circus of stations to to build connections between practical and theoretical work. At each station pupils measure out set masses / volumes to create a solution, then calculate the solution's concentration in mol/dm³. Once complete, pupils could rank each solution from most to least dilute.

Teacher tip

Equipment

Each station: common solute, spatula, weigh boat, balance, measuring cylinder, access to distilled water, conical flask / beaker + stirring rod

Content guidance

Risk assessment required - equipment
Depiction or discussion of violence or suffering

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.

Match each keyword to the correct definition.

Correct Answer:solution,a substance formed when a solute dissolves into a solvent

a substance formed when a solute dissolves into a solvent

Correct Answer:solute,a substance that has dissolved into a solvent

a substance that has dissolved into a solvent

Correct Answer:solvent,a substance into which a solute dissolves

a substance into which a solute dissolves

Q2.

Which solution will have the highest concentration?

Correct answer: Solution 1 contains 20 g of solute dissolved in 500 cm³ of water.

Solution 2 contains 15 g of solute dissolved in 500 cm³ of water.

Solution 3 contains 5 g of solute dissolved in 500 cm³ of water.

Solution 4 contains 1 g of solute dissolved in 500 cm³ of water.

Solution 5 contains 0.5 g of solute dissolved in 500 cm³ of water.

Q3.

Put these solutions in order from the least to the most concentrated.

Solution A has a concentration of 0.02 g/dm³.

Solution C has a concentration of 0.5 g/dm³.

Solution D has a concentration of 1 g/dm³.

Solution B has a concentration of 20 g/dm³.

Q4.

How many dm³ is 6500 cm³?

0.0065

Correct answer: 6.5

650

650 000

Q5.

Which equation correctly links mass, relative mass and moles?

moles = mass x relative mass

relative mass = moles x mass

Correct answer: mass = relative mass x moles

Q6.

What is the concentration of an aqueous solution if 20 g of solute is dissolved in 2 dm³ of water?

5 g/dm³

Correct answer: 10 g/dm³

20 g/dm³

40 g/dm³

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6 Questions

Q1.

How many cm³ are there in 3 dm³ of solution?

0.003

300

Correct answer: 3000

30 000

Q2.

Which of the following statements correctly describes the concentration of an aqueous solution?

Correct answer: It is the mass of solute dissolved in 1 dm³ of water, in g/dm³.

It is the mass of solute dissolved in 1 dm³ of water, in dm³/g.

It is the mass of solvent dissolved in 1 dm³ of water, in g/dm³.

It is the mass of solvent dissolved in 1 dm³ of water, in dm³/g.

Q3.

What is the mass of one mole of sodium chloride (NaCl)? Sodium has a relative atomic mass of 23.0; chlorine has a relative atomic mass of 35.5.

1 g

12 g

23 g

35.5 g

Correct answer: 58.5 g

Q4.

What is the mass of solute in a 1 dm³ solution with a concentration of 15 g/dm³?

10 g

Correct answer: 15 g

20 g

25 g

Q5.

Two 500 cm³ solutions of NaCl and KCl both have a concentration of 1 mol/dm³. Which of the following statements is true?

The NaCl solution contains more solute particles than the KCl solution.

The KCl solution contains more solute particles than the NaCl solution.

Correct answer: Both solutions contain an equal number of solute particles.

The number of solute particles depends on type of solute, not the concentration.

Q6.

If the concentration of a solution is 2 mol/dm³, how many moles of solute are there in 500 cm³ of solution?

0.5 moles

Correct answer: 1 mole

2 moles

4 moles