4.10 Solubility rules and preparing salts
5 exam questions worth 10 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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Which of these salts is insoluble in water?
Choose one answer.
Correct Not quite: the answer is Silver chloride
Mark scheme
C
Model answer
C: silver chloride is one of the insoluble chlorides.
Lead nitrate solution is mixed with sodium chloride solution.
Predict whether a precipitate forms and name it if it does.
Mark scheme
- yes, a precipitate forms (1)
- lead chloride (1)
Model answer
A precipitate of lead chloride forms, because lead chloride is insoluble.
Describe how to make a pure, dry sample of insoluble barium sulfate from barium chloride solution and sodium sulfate solution.
Mark scheme
- mix the solutions (1)
- filter to collect the precipitate (1)
- wash with distilled water (1)
- dry in a warm oven / between filter papers (1)
Model answer
Mix the two solutions to form a precipitate of barium sulfate. Filter the mixture, wash the solid on the filter paper with distilled water, then dry it in a warm oven.
When making sodium chloride by titration, the titration is repeated without the indicator. Explain why.
Mark scheme
- so the salt is not contaminated by the indicator (1)
Model answer
The indicator would contaminate the salt, so the reaction is repeated with the same volumes but no indicator.
Explain why potassium nitrate cannot be made by precipitation.
Mark scheme
- potassium nitrate is soluble (1)
- so it does not form a precipitate (it would need titration and crystallisation) (1)
Model answer
All potassium salts and all nitrates are soluble, so potassium nitrate cannot form a precipitate; it must be made by titration.
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