Question detail

What is the concentration in mol/dm³ of a solution containing 2 moles of potassium hydroxide (KOH) in 1 dm³ of solution?

Try the question, check the answer, then read the explanation to understand the curriculum point.

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At a glance

MCQ

Type

practice

Style

Topic

Amount of substance

Question

A. 2 mol/dm³
B. 1 mol/dm³
C. 0.5 mol/dm³
D. 4 mol/dm³

Answer

2 mol/dm³

Explanation

The correct option is 2 mol/dm³. Use Concentration in mol/dm3: concentration = moles / volume. The worked result is 2 mol. 2 mol/dm³ is the best answer because it directly supports the AQA A-Level Chemistry objective to apply the mole to electrons, atoms, molecules, ions, formula units and equations. 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

Misunderstanding the Mole Concept

Students often confuse the mole with the mass of a substance, thinking that the mole is a measure of weight rather than a measure of quantity.

To clarify, remember that the mole is a unit that measures the amount of substance. Use the formula: n = m / Mr, where n is the number of moles, m is the mass in grams, and Mr is the relative formula mass. For example, if you have 18 grams of water (H₂O), calculate the moles as follows: n = 18 g / 18 g/mol = 1 mol. Thus, the answer is 1 mol.

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