Question

Select the set of reactants that will form a precipitate upon mixing. NaCl(aq) + KBr(aq) BaCl2(aq) + LiOH(aq) NaClO4(aq) + Fe(NO3)2(aq) Na3PO4(aq) + H2SO4(aq) Li2S(aq) + NiCl2(aq)

Answer 1

Li2S(aq) + NiCl2 (aq) → 2LiCl (aq) + NiS (s)

NiS is insoluble salt. This is Ni+2 salt. This salt forms precipitate in aqueous solution.

SOLUBILITY RULES Soluble Salts 1. All group IA or 1st group (Lit, Nat, Kt, Rbt, Cs+) salts and all NH4+ salts are soluble. 2. All sulphates are soluble (except BaSO4, PbSO4, SrS04). 3. All halides (F, CI, Br", I') are soluble (except those of Agt, Hg22+, Pb2+). 4. All nitrates, acetates and perchlorates are soluble (except AgC2H302, KC104). Insoluble Salts 1) All metal hydroxides are insoluble (except those of groups IA, IIA, and NH4+, but Mg(OH)2 is insoluble). 2) All carbonates are insoluble except those of Group IA and NH4*. From the data a) NaCl (aq) + KBr (aq) → NaBr(aq) + KCl(aq) Na and K are 1st group elements so salts are solubile. b) BaCl2 (aq) + LiOH (aq) → Ba(OH)2 (aq) + 2LICI (aq) Ba is 2nd group element, 2nd group element hydroxides are soluble. Li is 1st group element Li salts are soluble. c) 2NaC104(aq) + Fe(NO3)2 (aq) → Fe(C104)2 (aq) + 2NaNO3 (aq) Perchlorates are soluble. Na is 1st group element so Na salts are soluble. d) 2Na3PO4(aq) + 3H2SO4 (aq) + 3Na2SO4 (aq) + 2H3PO4 (aq) e) Li2S(aq) + NiCl2 (aq) 2LiCi (aq) + NiS (s) NiS is insoluble salt. This is Ni*- salt. This salt forms precipitate in aqueous solution.