Chemical Equilibrium Question 3
Question 3 - 2024 (31 Jan Shift 1)
For the given reaction, choose the correct expression of $\mathrm{K}_{\mathrm{C}}$ from the following :-
$\mathrm{Fe}{(\mathrm{aq})}^{3+}+\mathrm{SCN}{(\mathrm{aq})}^{-} \rightleftharpoons(\mathrm{FeSCN})_{(\mathrm{aq})}^{2+}$
(1) $\mathrm{K}_{\mathrm{C}}=\frac{\left[\mathrm{FeSCN}^{2+}\right]}{\left[\mathrm{Fe}^{3+}\right]\left[\mathrm{SCN}^{-}\right]}$
(2) $\mathrm{K}_{\mathrm{C}}=\frac{\left[\mathrm{Fe}^{3+}\right]\left[\mathrm{SCN}^{-}\right]}{\left[\mathrm{FeSCN}^{2+}\right]}$
(3) $\mathrm{K}_{\mathrm{C}}=\frac{\left[\mathrm{FeSCN}^{2+}\right]}{\left[\mathrm{Fe}^{3+}\right]^{2}\left[\mathrm{SCN}^{-}\right]^{2}}$
(4) $\mathrm{K}_{\mathrm{C}}=\frac{\left[\mathrm{FeSCN}^{2+}\right]^{2}}{\left[\mathrm{Fe}^{3+}\right]\left[\mathrm{SCN}^{-}\right]}$
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Answer (1)
Solution
$\mathrm{K}_{\mathrm{C}}=\frac{\text { Products ion conc. }}{\text { Reactants ion conc. }}$
$\mathrm{K}_{\mathrm{C}}=\frac{\left[\mathrm{FeSCN}^{2+}\right]}{\left[\mathrm{Fe}^{3+}\right]\left[\mathrm{SCN}^{-}\right]}$
