(a)i) How would an aqueous solution of iron (II) tetraoxosulphate (VI) be converted into an aqueous solution of magnesium tetraoxosulphate (VI)?
(ii) Write a balanced equation for the reaction in (a)(i) above
(b)(i) Why are some compounds recrystallized after preparation?
(ii) Outline the steps in recrystallization
(C)(i) Name two gases that can cause color changes in an acidified solution of potassium heptaoxodichromate (VI)
(ii) State the color change expected in (c)i) above
Explanation
a)i) How would an aqueous solution of iron (II) tetraoxosulphate (VI) be converted into an aqueous solution of magnesium tetraoxosulpiiate (VI): Add magnesium ribbon/powder to the iron (II) 1tetraoxosulphate (vi) solution and stir.
ii) Write a balanced equation for the reaction in (a)(i) above:
Mg\(_{(s)}\) +FeSO\(_{4(aq)}\) \(\to\) MgSO\(_{4(aq)}\) + Fe\(_{(s)}\)
(b) (I) Why are some compounds recrystallized after preparation? To make the compound pure/purify the compound/purification/to remove impurities because the compound is impure.
(ii) Outline the steps in recrystallization:
(1) Put the solid in a beaker and add appropriate/suitable solvent.
(2) Heat the mixture to dissolve the solid.
(3) Filter the hot mixture/solution.
(4) Concentrate the filter.
(5) Cool the filtrate for crystals to form.
(6) Filter the crystals off; wash with some cold water and dry crystals in an oven
(c)(i) Name two gases that can cause colour changes in an acidified solution of potassium heptaoxodichromate (VI):
Sulphur(IV)oxide, hydrogen sulphide, ethene, ethyne, propene, propyne, butene, butyne.
(ii) State the colour change expected in (c)(i) above;
Potassium heptaoxodichromate (IV) turns from orange/yellow to green