Reversing the calculations
3 marks · Easy20.0 cm³ of a solution contains 0.00400 mol of a substance.
Calculate the volume of the solution in dm³.
Calculate the concentration of the solution in mol/dm³.
State the formula used for this calculation.
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
(a) 0.0200 dm³
(b) 0.200 mol/dm³
(c) concentration (mol/dm³) = number of moles / volume (dm³)
Common mistakes: Forgetting to convert volume units; Incorrect rearrangement of formula
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Converts 20.0 cm³ to 0.0200 dm³
M2 (b) · 1 mark · Uses concentration = moles / volume; 0.00400 / 0.0200 = 0.200 mol/dm³
B1 (c) · 1 mark · States the correct formula for concentration in terms of moles and volume.
Worked solution
a) 20.0 cm³ = 20.0 / 1000 = 0.0200 dm³
b) Concentration = 0.00400 / 0.0200 = 0.200 mol/dm³
c) The formula used: concentration (mol/dm³) = number of moles / volume (dm³)