Calculations with equations involving solutions
3 marks · EasyA student prepares solutions of nitric acid with different concentrations. The table shows the volume and concentration of nitric acid used in each experiment.
| Experiment | Volume (cm³) | Concentration (mol/dm³) |
|---|---|---|
| 1 | 25 | 0.20 |
| 2 | 40 | 0.10 |
| 3 | 50 | 0.16 |
Calculate the number of moles of nitric acid in each experiment. Give your answers to two decimal places.
Experiment 1:
Experiment 2:
Experiment 3:
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.
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(a) 0.01 mol
(b) 0.004 mol
(c) 0.008 mol
Common mistakes: Forgetting to convert cm³ to dm³; Incorrect multiplication
Show mark scheme and worked solution
Marking points
M1 (a) · 0.5 marks · Method for converting volume to dm³ in Experiment 1 (÷1000)
A1 (a) · 0.5 marks · Correct number of moles in Experiment 1 to two decimal places (follow-through)
M2 (b) · 0.5 marks · Method for converting volume to dm³ in Experiment 2 (÷1000)
A2 (b) · 0.5 marks · Correct number of moles in Experiment 2 to appropriate significant figures (follow-through)
M3 (c) · 0.5 marks · Method for converting volume to dm³ in Experiment 3 (÷1000)
A3 (c) · 0.5 marks · Correct number of moles in Experiment 3 to appropriate significant figures (follow-through)
Worked solution
Use the equation: number of moles = volume (dm³) × concentration (mol/dm³).
First convert each volume from cm³ to dm³ by dividing by 1000.
Experiment 1: Volume = 25 cm³ = 0.025 dm³, Concentration = 0.20 mol/dm³
Rounded to two decimal places: 0.01 mol
Experiment 2: Volume = 40 cm³ = 0.040 dm³, Concentration = 0.10 mol/dm³
Experiment 3: Volume = 50 cm³ = 0.050 dm³, Concentration = 0.16 mol/dm³