Chemistry 5070 · O Level · Preparation of salts

Preparation of salts — practice question

Ammonium sulfate is a salt used as a fertiliser. A student is making some ammonium sulfate crystals by neutralisation. She uses dilute sulfuric acid together with aqueous ammonia. The diagrams show some of the apparatus available to the student.
(a)[1]

The student measures $25.0\text{ cm}^3$ of aqueous ammonia into a conical flask. Write down the letter for the apparatus she should use to measure the aqueous ammonia. Give the name of this apparatus.

(b(i))[1]

State the name of this apparatus.

(b(ii))[2]

State the colour of methyl orange indicator in: • aqueous ammonia • dilute sulfuric acid?

(c)[6]

At the end-point the student notes that $12.5\text{ cm}^3$ of $0.100\text{ mol dm}^{-3}$ sulfuric acid has neutralised $25.0\text{ cm}^3$ of $0.100\text{ mol dm}^{-3}$ ammonia. Devise an experiment to prepare a pure sample of ammonium sulfate crystals. You should use: • $0.100\text{ mol dm}^{-3}$ sulfuric acid • $0.100\text{ mol dm}^{-3}$ ammonia • the apparatus normally found in a chemistry laboratory.

(d(i))[1]

What is the volume of gas in the gas syringe?

(d(ii))[1]

After the gas has been gathered, damp blue litmus paper and damp red litmus paper are placed in the gas. What happens to the colour of: • the damp blue litmus paper • the damp red litmus paper?

Worked solution & mark scheme

This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: B — (volumetric) pipette

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