Concentration of solutions: using moles (RAM 1 d.p.) | Chemistry

Starter quiz

Match each keyword to the correct definition.

solution

⇔

a substance formed when a solute dissolves into a solvent ✓

solute

⇔

a substance that has dissolved into a solvent ✓

solvent

⇔

a substance into which a solute dissolves ✓
Which solution will have the highest concentration?

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.
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.
How many dm³ is 6500 cm³?

0.0065

6.5 ✓

650

650 000
Which equation correctly links mass, relative mass and moles?

moles = mass x relative mass

relative mass = moles x mass

mass = relative mass x moles ✓
What is the concentration of an aqueous solution if 20 g of solute is dissolved in 2 dm³ of water?

5 g/dm³

10 g/dm³ ✓

20 g/dm³

40 g/dm³

How many cm³ are there in 3 dm³ of solution?

0.003

30

300

3000 ✓

30 000
Which of the following statements correctly describes the concentration of an aqueous solution?

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.
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

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

10 g

15 g ✓

20 g

25 g
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.

Both solutions contain an equal number of solute particles. ✓

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

1 mole ✓

2 moles

4 moles

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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.

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.

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.