Making insoluble salts
3 marks · EasyA student mixes different pairs of solutions and records whether a precipitate forms. The results are shown in the table below.
| Solution 1 | Solution 2 | Observation |
|---|---|---|
| Magnesium sulfate | Sodium carbonate | White precipitate |
| Potassium chloride | Sodium nitrate | No precipitate |
| Calcium nitrate | Sodium sulfate | White precipitate |
Use the table to answer the questions.
Which pair of solutions does NOT produce an insoluble salt?
Name one insoluble salt formed in these reactions.
Give a reason why no precipitate forms when potassium chloride and sodium nitrate are mixed.
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) Potassium chloride and sodium nitrate
(b) Magnesium carbonate or calcium sulfate
(c) All potassium and sodium salts are soluble
Common mistakes: Stating all salts are insoluble; Generic statements about salts
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly identifies potassium chloride and sodium nitrate as not producing an insoluble salt.
B2 (b) · 1 mark · Names an insoluble salt such as magnesium carbonate or calcium sulfate.
B3 (c) · 1 mark · Gives a correct reason: all sodium and potassium salts are soluble.
Worked solution
a) Potassium chloride and sodium nitrate do not form an insoluble salt (no precipitate).
b) Magnesium carbonate (from magnesium sulfate and sodium carbonate) or calcium sulfate (from calcium nitrate and sodium sulfate) are insoluble salts formed.
c) No precipitate forms when potassium chloride and sodium nitrate are mixed because all sodium and potassium salts are soluble in water.