Calculations with equations involving solutions

2 marks · Normal

Calculate the number of moles of potassium nitrate, KNO₃, in 25 cm³ of a solution with concentration 0.40 mol/dm³.

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0.010 mol (±0.001)

Also accept: 1.0 × 10^{-2} mol; 0.01 mol

Common mistakes: Failing to convert cm³ to dm³ (using 25 instead of 0.025)

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Marking points

M1 · 1 mark · Converts 25 cm³ to 0.025 dm³ or uses the correct moles formula.

A1 · 1 mark · Correct calculation of moles: 0.01 mol. (follow-through)

Worked solution

Convert 25 cm³ to dm³: 25 ÷ 1000 = 0.025 dm³.

Number of moles of KNO₃ = 0.01 mol.