Payal posted an Question
September 29, 2020 • 01:01 am 30 points
  • IIT JAM
  • Chemistry (CY)

Why are group 4 salts not precipitated when group 2 test is carried out(on addition of h2s)in salt analysis?

Why are group 4 salts not precipitated when group 2 test is carried out(on addition of H2S)in salt analysis?

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    Dinesh khalmaniya 1 best-answer

    check it

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    Solubility product of sulphides of II group radicals are less than solubility product of sulphides of IV group. So to pricipitate II group radicals as sulphides little S2-are sufficient. In presence of Dil HCl little S2- are released due to the common ion effects. In IV group the ionisation of H2S is favoured by the use of NH4OH

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    Priyanshu kumar Best Answer

    Solubility product of sulphides of II group radicals are less than solubility product of sulphides of IV group. So to pricipitate II group radicals as sulphides little S2-are sufficient. In presence of Dil HCl little S2- are released due to the common ion effects. In IV group the ionisation of H2S is favoured by the use of NH4OH

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    In qualitative analysis of cations of second group, H2​S is passed in presence of HCl. Due to common ion effect, ionisation of H2​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 (Ksp​). Here, fourth group cations are not precipitated because they required for exceeding their ionic product to their solubility products and highers sulphide ions concentration due to their higher (Ksp​)  which is not obtained here due to common ion effect.

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