Question

Which one of the following would form a precipitate when mixed with LiOH?

Answer 1

Answer:

ZnBr2

Explanation:

KNO3 + LiOH -------> no reaction

This is because KNO3 and LiOH completely ionize.in water and form neutral solutions.Since both are neutral no reaction occurs

NH4Cl + LiOH -----> NH3 (aq) + H2O (l) + LiCl(aq)

None of the above products are precipitates

Ca(C2H3O2)2 + 2LiOH -----> Ca(OH)2 (aq) + 2LiC2H3O2 (aq)

ZnBr2 + 2LiOH -----> Zn(OH)2 (s) + LiBr2 ( aq)

Zn(OH)2 thus formed is a white precipitate

However when excess LiOH is added Zn(OH)2 precipitate will dissolve to give a clear solution of Li2ZnO2 .

You can remember this by the fact that Na,K,Rb,Cs,Ca,Sr,Ba hydroxides are soluble in water and all other hydroxide are precipitated in water

Zn(OH)2 (s) + 2 LiOH ------> Li2ZnO2(aq) + 2 H2O ( l)