Question detail
Calculate the concentration in g/dm³ of a solution containing 2 moles of potassium sulfate (K2SO4) in 1 dm³ of solution. The relative formula mass (Mr) of K2SO4 is 174 g/mol.
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Amount of substance
Question
- A. 348 g/dm³
- B. 87 g/dm³
- C. 174 g/dm³
- D. 69 g/dm³
Answer
348 g/dm³
Explanation
The correct option is 348 g/dm³. Use Concentration in g/dm3: concentration = mass / volume. The worked result is 348 g. 348 g/dm³ is the best answer because it directly supports the AQA A-Level Chemistry objective to calculate amounts using mass, Mr and moles. This reasoning is anchored to The mole and the Avogadro constant in Amount of substance, and it separates mole from similar A-Level ideas rather than relying on a vague recall statement. Other options are weaker if they use the wrong evidence, calculation, mechanism, observation, unit, or conclusion for this subtopic.
Common mistake
Common Mistake in Mole Calculations
Students often forget to convert the mass into grams before using the formula to calculate moles.
Always ensure that the mass is in grams when using the formula moles = mass / Mr. For example, if the mass is given as 2 kg, convert it to grams (2000 g) before substituting into the formula. Then, substitute: moles = 2000 g / Mr. Calculate the final answer in moles.
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