Q23 / 220 · NTA Abhyas (NEET) 2020 · Chemistry · Ionic Equilibrium

A solution which is 10-3 M each in Mn2+,Fe2+,Zn2+ and Hg2+ is treated with 10-16 M sulphide ion. If Ksp of MnS , FeS, ZnS and HgS are 10-13,10-18,10-24 and 10-53 respectively. Which one will precipitate first?

  • A
    FeS
  • B
    MgS
  • Correct answer
    C
    HgS
  • D
    ZnS

Solution

[S2-] needed for precipitation of
FeS=10-1810-3=10-15M
MnS=10-1310-3=10-10M
HgS=10-5310-3=10-50M
ZnS=10-2410-3=10-21M
Thus, minimum [S2-] is for HgS and so it will be precipitated first.

Hence, the correct answer is option: 'C'.

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