Chemistry · May / June 2024 · Paper 41 · Question 5

M1 lead(II) nitrate(1)

M2 sodium bromide /

potassium bromide /

ammonium bromide(1)

M1 filter precipitate or lead(II) bromide or solid or residue(1)

M2 wash the residue with distilled water AND dry e.g. between filter papers(1)

Pb2+(aq) + 2Br–(aq) → PbBr2(s)

M1 PbBr2 as the only product (1)

M2 Pb2+ + 2Br– as the only reactants in a balanced equation(1)

M3 state symbols

(aq) + (aq) → (s)(1)

M1 acidified aqueous potassium manganate(VII) (1)

M2 purple to colourless (1)

M1 2CoO + 4NO2 (1)

M2 8H2O (1)

M1 heat again and weigh again

OR

repeat steps 2 and 3(1)

M2 until mass is constant (1)

M1 0.005 / 5 ×10–3 (1)

M2 0.63 (1)

M3 (0.63 / 18 =) 0.035 (1)

M4 (0.035 ÷ 0.005 =) 7 (1)