Salt preparations
4 marks · NormalIron(II) sulfate can be made by reacting an acid with a suitable base in the laboratory.
Name two reactants you could use to prepare iron(II) sulfate.
Write the balanced chemical equation for this reaction.
Describe the steps you would take to obtain pure iron(II) sulfate crystals from the reaction mixture.
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.
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(a) Dilute sulfuric acid and iron(II) oxide.
(b) \ce{FeO + H2SO4 -> FeSO4 + H2O}
(c) Add excess iron(II) oxide to sulfuric acid, stir, and warm gently. Filter to remove unreacted base, then evaporate the filtrate to form crystals. Allow the crystals to cool then pat dry.
Also accept: Iron(II) carbonate for b (with correct balanced equation)
Common mistakes: Not removing excess solid by filtration; Not using excess base; Incorrect chemical equation
Show mark scheme and worked solution
Marking points
B1 (a(b)) · 1 mark · Identifies two correct reactants (e.g., iron(II) oxide and dilute sulfuric acid).
B2 (a(c)) · 1 mark · Correct balanced equation for the reaction (accept iron(II) carbonate with correct balanced equation).
M1 (a(c)) · 1 mark · Describes filtration to remove excess solid.
M2 (a(c)) · 1 mark · Describes evaporation/crystallisation to obtain pure crystals.
Worked solution
a) The two reactants are iron(II) oxide and dilute sulfuric acid.
c) Add excess iron(II) oxide to the sulfuric acid, warm and stir until no more reacts. Filter out excess oxide, evaporate the filrate to concentrate, cool to form crystals, collect and dry the crystals.