AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Students should be able to: calculate the mass of solute in a given volume…
Full specification wording
Concentration of solutions: Students should be able to: calculate the mass of solute in a given volume of solution of known concentration in terms of mass per given volume of solution (HT only) explain how the mass of a solute and the volume of a solution is related to the concentration of the solution. AQA GCSE Chemistry 8462. GCSE e
Concentration links the mass of solute to the volume of solution.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 2 of 2
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Concentration links the mass of solute to the volume of solution. For a solution of known concentration in g dm⁻³, mass of solute = concentration × volume in dm³. For example, 250 cm³ of a 40 g dm⁻³ solution contains 40 × 0.250 = 10 g of solute. Rearranging gives concentration = mass ÷ volume and volume = mass ÷ concentration. If concentration is given in mol dm⁻³, first calculate moles using n = c × V, then convert to mass using m = n × Mᵣ. Always convert cm³ to dm³ by dividing by 1000. This relationship allows prediction of how much solute is needed or present in any given volume.
What earns the marks
- Use the equation mass of solute = concentration × volume of solution when concentration is in g dm⁻³.
- Convert volume from cm³ to dm³ by dividing by 1000 before substituting.
- Rearrange the relationship to find concentration or volume when the other two quantities are known.
- Convert between moles and mass using n = c × V and m = n × Mᵣ when concentration is in mol dm⁻³.
- Explain that for a fixed mass of solute, increasing the volume decreases the concentration.
Common mistakes and how to put them right
Forgetting to convert cm³ to dm³.
Put it right: The corrected method divides the volume in cm³ by 1000.
Mixing units, such as using cm³ with g dm⁻³.
Put it right: The corrected approach uses consistent units throughout.
Confusing mass of solute with concentration.
Put it right: Concentration is mass per unit volume, not the total mass.
Exam tips
- Write down the equation and rearrange it before substituting numbers.
- Convert all volumes to dm³ at the start of the calculation.
- Check that the final answer has the correct unit, such as g or g dm⁻³.
Try the lesson
The start of the Concentration of solutions: Students should be able to: calculate the mass of solute in a given volume of solution of known concentration in terms of mass per given volume of solution (HT only) explain how the mass of a solute and the volume of a solution is related to the concentration of the solution. AQA GCSE Chemistry 8462. GCSE e lesson, made from checked teaching notes for this specification point.
Have a go first
A solution has a concentration of 20 g/dm³. What mass of solute is dissolved in 1 dm³ of this solution?
Listen
Concentration links the mass of solute to the volume of solution. For a solution of known concentration in g dm⁻³, mass of solute = concentration × volume in dm³. For example, 250 cm³ of a 40 g dm⁻³ solution contains 40 × 0.250 = 10 g of solute. Rearranging gives concentration = mass ÷ volume and volume = mass ÷ concentration. If concentration is given in mol dm⁻³, first calculate moles using n = c × V, then convert to mass using m = n × Mᵣ. Always convert cm³ to dm³ by dividing by 1000. This relationship allows prediction of how much solute is needed or present in any given volume. A strong answer earns marks for these points. Use the equation mass of solute = concentration × volume of solution when concentration is in g dm⁻³. Convert volume from cm³ to dm³ by dividing by 1000 before substituting. Rearrange the relationship to find concentration or volume when the other two quantities are known. Convert between moles and mass using n = c × V and m = n × Mᵣ when concentration is in mol dm⁻³. A common slip: Confusing mass of solute with concentration. Instead, concentration is mass per unit volume, not the total mass. Exam tip: Write down the equation and rearrange it before substituting numbers.
Key words
Say what each word means before you turn the card.
Concentration calculations
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Mass–volume relationships
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Unit conversion
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Moles and concentration
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See every definition
- Concentration calculations
- The mass of solute is found from concentration multiplied by volume, and the relationship can be rearranged to find concentration or volume.
- Mass–volume relationships
- For a fixed mass of solute, increasing the volume decreases the concentration, and the mass of solute and volume of solution are related to the concentration.
- Unit conversion
- Volume in cm³ is converted to dm³ by dividing by 1000 before substituting, and consistent units are used throughout.
- Moles and concentration
- When concentration is in mol dm⁻³, moles are first calculated using n = c × V, then converted to mass using m = n × Mᵣ.
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