NH4Cl is added before (NH4)2CO3 in the group V separation mainly to

keep Mg^2+ in solution by lowering the carbonate ion concentration, so that MgCO3 does not precipitate

increase the hydroxide ion concentration

keep Mg^2+ in solution by lowering the carbonate ion concentration, so that MgCO3 does not precipitate

oxidise Ba^2+ to a higher oxidation state

make the solution strongly acidic so that all carbonates dissolve

NEET levelSingle correct optionDifficulty 1 of 3qc115

$NH X_{4} Cl$ is added before $(NH X_{4}) X_{2} CO X_{3}$ in the group V separation mainly to

Aincrease the hydroxide ion concentration
Bkeep $Mg X^{2 +}$ in solution by lowering the carbonate ion concentration, so that $MgCO X_{3}$ does not precipitate
Coxidise $Ba X^{2 +}$ to a higher oxidation state
Dmake the solution strongly acidic so that all carbonates dissolve

NH X_{4} X^{+}

suppresses the hydrolysis/ionisation that supplies carbonate and lowers

[CO X_{3} X^{2 -}]

. Only the very insoluble

BaCO X_{3}

SrCO X_{3}

and

CaCO X_{3}

then precipitate, while the more soluble

MgCO X_{3}

stays in solution for group VI. It does not raise

[OH X^{-}]

or make the medium acidic.