Measuring solubility [chemistry only]
4 marks · NormalThe table below shows the solubility of two salts in water at different temperatures.
| Temperature (°C) | Solubility of Salt X (g/100g water) | Solubility of Salt Y (g/100g water) |
|---|---|---|
| 20 | 32 | 13 |
| 40 | 44 | 19 |
| 60 | 56 | 25 |
| 80 | 68 | 31 |
On the axes below, plot the solubility curves for Salt X and Salt Y using the data from the table.
Use a suitable scale and label both curves clearly.
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
Must show: Both sets of points accurately plotted, Axes labelled: Temperature (°C), Solubility (g/100g water), Both curves drawn smoothly through or near correct points, Curves for Salt X and Salt Y clearly identified
Also accept: Accept small plotting errors within one square; Accept curves neatly joined by straight lines for each salt
Common mistakes: missing axis labels; unclear identification of curves; points not accurately plotted
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Axes labelled with correct variables and units, suitable scale chosen.
M2 (a) · 1 mark · All data points plotted accurately for Salt X (within one small square).
M3 (a) · 1 mark · All data points plotted accurately for Salt Y (within one small square).
A1 (a) · 1 mark · Both solubility curves drawn smoothly or joined by line segments, and each curve clearly labelled.
Worked solution
(i) Draw axes: horizontal axis for temperature (°C), 20 to 80; vertical axis for solubility (g/100g water), 10 to 70.
(ii) Plot Salt X: (20,32), (40,44), (60,56), (80,68).
(iii) Plot Salt Y: (20,13), (40,19), (60,25), (80,31).
(iv) Draw smooth curves or join with line segments for each salt.
(v) Clearly label each curve as Salt X and Salt Y.