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Edexcel IGCSE Chemistry 2.39 soluble salt preparation

Edexcel IGCSE Chemistry 2.39 soluble salt preparation
Edexcel IGCSE Chemistry syllabusChemistry 4CH1First assessment 2019

Practise soluble-salt questions by adding excess solid, filtering unreacted material and crystallising pure hydrated salts.

How this is tested

  • Explain why excess metal or insoluble reactant ensures all the acid has reacted.
  • Sequence filtration, heating, cooling and drying to obtain pure hydrated salt crystals.
  • Link filtering to removing excess zinc, magnesium or other unreacted insoluble solid.

Question 6

[Maximum number: 6]

A student uses the reaction between magnesium and dilute hydrochloric acid to prepare crystals of hydrated magnesium chloride.

The student adds excess magnesium powder to hydrochloric acid.
This is the equation for the reaction.

Mg( s)+2HCl(aq)→MgCl2(aq)+H2( g)\mathrm{Mg}(\mathrm{~s})+2 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{MgCl}_{2}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{~g})

Question 6(c)

(a)

Give a reason why the student adds an excess of magnesium to the dilute hydrochloric acid.

[ 1 ]

Question 6(d)

(b)

Describe what the student should do to the mixture formed in (c) to produce pure, dry crystals of hydrated magnesium chloride.

[ 5 ]