JEE Main & Advanced AIEEE Solved Paper-2004

  • question_answer
    In a cell that utilises the reaction, \[Zn(s)+2{{H}^{+}}(aq)\xrightarrow{{}}Z{{n}^{2+}}(aq)+{{H}_{2}}(g)\] addition of\[{{H}_{2}}S{{O}_{4}}\]to cathode compartment, will

    A) lower the E and shift equilibrium to the left

    B) lower the E and shift the equilibrium to the right

    C) increase the E and shift the equilibrium to the right

    D) increase the E and shift the equilibrium to the left

    Correct Answer: C

    Solution :

    \[Zn(s)\,+2{{H}^{+}}\,\xrightarrow{\,}\,Z{{n}^{2+}}\,(aq)+{{H}_{2}}(g)\] Reaction quotient \[Q=\frac{[Z{{n}^{2+}}]}{{{[{{H}^{+}}]}^{2}}}\] Corresponding cell is \[\underset{Anode}{\mathop{\underset{-}{\mathop{Zn|Z{{n}^{2+}}({{C}_{1}})\,|}}\,}}\,\underset{Cathode}{\mathop{\underset{+}{\mathop{|{{H}^{+}}(aq)|Pt({{H}_{2}})}}\,}}\,\] and        \[{{E}_{cell}}\,=E_{cell}^{o}\,-\frac{0.0591}{2}\log K\] \[=E_{cell}^{o}\,-\frac{0.0591}{2}\log \,\frac{[Z{{n}^{2+}}]}{{{[{{H}^{+}}]}^{2}}}\] \[=E_{cell}^{o}\,+\frac{0.0591}{2}\log \,\frac{{{[{{H}^{+}}]}^{2}}}{[Z{{n}^{2+}}]}\] If \[{{H}_{2}}S{{O}_{4}}\] is added to cathodic compartment. (towards reactant side), then Q decreases (due to increase in\[{{H}^{+}}\]). Hence, equilibrium is displaced towards right and \[{{E}_{cell}}\] increases,


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