Concentrations of solutions

2 marks · Normal

Calculate the concentration in mol/dm³ of a solution containing 5.60 g of potassium hydroxide (KOH, Ar: K = 39, O = 16, H = 1) in 500 cm³ of solution.

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

Show answer

0.2 mol/dm³ (±0.01)

Also accept: 0.20 mol/dm³; 0.200 mol/dm³

Common mistakes: Not converting cm³ to dm³; Using wrong Mr

Show mark scheme and worked solution

Marking points

M1 · 1 mark · Converts 500 cm³ to 0.5 dm³ or calculates number of moles: 5.60/56 = 0.1 mol

A1 · 1 mark · Correct concentration: 0.1 / 0.5 = 0.2 mol/dm³ (accept 0.20, 0.200) (follow-through)

Worked solution

Mr(KOH) = 39 + 16 + 1 = 56

Volume = 500 cm³ = 0.5 dm³