JEE Main levelSingle correct optionDifficulty 2 of 3qc021
Among the following hydroxides, the one that is precipitated when NHX4OH is added to a solution containing excess NHX4Cl is
ACa(OH)X2
BMn(OH)X2
CMg(OH)X2
DFe(OH)X3
Answer: D
The common ion effect of NHX4Cl keeps [OHX−] low. Fe(OH)X3 has an extremely small Ksp (about 10−38) and precipitates, whereas Mn(OH)X2, Mg(OH)X2 and Ca(OH)X2 have much larger Ksp values and remain dissolved.