Question
What is the necessity of adding NH4OH in group V analysis?
Solution
Cations of group V (Ba2+, Sr2+, Ca2+) are precipitated as their carbonates on adding ammonium carbonate to their solutions containing NH4Cl and NH4OH. The necessity of adding ammonium hydroxide arises due to the fact that ammonium carbonate solution usually contains a large amount of ammonium bicarbonate. Since the bicarbonates of Ba2+, Sr2+, Ca2+ are soluble and do not get precipitated, therefore, ammonium hydroxide is added to convert NH4HCO3 into (NH4)2CO3.
