DKNO3, NaOH, Na2SO4[1]
A gives a red-brown precipitate of iron(III) hydroxide, B gives a white precipitate of barium sulfate, and C is blue because of the copper(II) ions.
BAmmonia gas is produced.[1]
The acid reacts with the carbonate to give carbon dioxide, which is acidic. Ammonia is given off by ammonium salts with an alkali, not with an acid.
Abarium nitrate solution[1]
Barium nitrate gives a white precipitate of barium sulfate with sulfuric acid only. The other reagents give the same result with both acids.
Dsodium nitrate[1]
Warming with sodium hydroxide drives off the ammonium ions as ammonia. Barium sulfate is filtered off, leaving sodium and nitrate ions in the filtrate.
Czinc carbonate[1]
The gas is carbon dioxide, so the solid is a carbonate. The hydroxide dissolves in excess aqueous ammonia, so the cation is zinc. The chloride in test 1 comes from the hydrochloric acid.
A: calcium carbonate, CaCO3 [1]
C: calcium chloride, CaCl2 [1]
D: carbon dioxide, CO2 [1]
E: calcium hydroxide, Ca(OH)2 [1]
Ca2+(aq) + 2OH−(aq) → Ca(OH)2(s) [1]
Aqueous barium nitrate: no observable change. [1]
Aqueous silver nitrate: a white precipitate forms. [1]
T: iron(II) chloride [1]
U: carbon dioxide [1]
V: iron(II) hydroxide [1]
W: silver chloride [1]
Iron(II), carbonate and nitrate ions (all three needed). Chloride is not accepted, as it could have come from the hydrochloric acid. [1]
Any one, e.g. CO2 + Ca(OH)2 → CaCO3 + H2O or Fe2+(aq) + 2OH−(aq) → Fe(OH)2(s) [1]
Calcium hydroxide reacts with ammonium-based fertilisers to form ammonia gas, which escapes into the atmosphere. [1]
This results in the loss of nitrogen from the fertiliser, which plants need for growth. [1]