Exams › JEE Main › Chemistry
H2S gas when passed through a solution of cations containing HCl, precipitates the cations of second group of qualitative analysis but not those belonging to the fourth group. It is because
- presence of HCl decreases the sulphide ion concentration.
- solubility product of group II sulphides is more than that of group IV sulphides.
- presence of HCl increases the sulphide ion concentration.
- sulphides of group IV cations are unstable in HCl.
Correct answer: presence of HCl increases the sulphide ion concentration.
Solution
HCl is a strong acid that completely dissociates in water, increasing the concentration of H⁺ ions. This, in turn, increases the concentration of HS⁻ ions, which react with the cations to form precipitates.
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