A) presence of \[\text{HCl}\]decreases the sulphide ion concentration
B) presence of\[\text{HCl}\] increases the sulphide ion concentration
C) solubility product of group II sulphides is more than that of group IV sulphides
D) sulphides of group IV cations are. Unstable in \[\text{HCl}\]
Correct Answer: B
Solution :
In qualitative analysis of cations of second group, \[{{\text{H}}_{\text{2}}}\text{S}\]is passed in presence of HCl. Due to common ion effect, ionisation of \[{{\text{H}}_{\text{2}}}\text{S}\]decreases and less sulphide ions are obtained. These sulphide ions are sufficient for the precipitation of second group cations in form of their sulphides due to lower value of their solubility product \[({{K}_{sp}}).\] Here, fourth group cations are not precipitated because they require for exceeding their ionic product to their solubility products and higher sulphide ions concentration due to their higher \[{{K}_{sp}}\]which is not obtained here due to common ion effect.
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