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Question:

For the following reaction, equilibrium constant Kc at 298 K is 1.6×10¹⁷. Fe²⁺(aq) + S²⁻(aq)⇌FeS(s) When equal volumes of 0.06 M Fe²⁺(aq) and 0.2 M S²⁻(aq) solution are mixed, then the equilibrium concentration of Fe²⁺(aq) is found to be Y×10⁻¹⁷ M. The value of Y is __________.

8.92

Solution:

Correct option is A. 8.92
Fe(aq)²⁺ 0.06 M
After mixing 0.03 M

  • S(aq)²⁻ 0.2 M 0.1 M
    ⇌FeS(s)
    KC=1.6×10¹⁷
    ? 0.07 M
    1.6×10¹⁷=1/[Fe²⁺]×0.07
    or [Fe²⁺]=10⁻¹⁷/1.6×0.07=10⁻¹⁵/1.12=100/1.12×10⁻¹⁷=8.928×10⁻¹⁷=Y×10⁻¹⁷
    Answer after rounding is=8.93
    Answer after truncation is=8.92.