InterviewSolution
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InterviewSolution
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The standard electrode potential corresponding to the reaction ` Au^(3+) (aq) + 3e^(-) rarr Au (s)` is `1. 42 V`. This implies that . (i) gold dissolves in ` 1M HCl` (ii) metallic gole will be precipitated on passing hydrogen gas through gold salt solution (iii) gold does not dissolve in ` 1M HCl` solution (iv) metallic gold will not be precipitated on passing hydrogen gas through gold salt solution.A. (i), (ii)B. (i), (iv)C. (ii), (iv)D. (ii), (iii) |
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Answer» Correct Answer - D Gold will dissolve in `1 M HCl` if it gets oxidized and ` H+` ions fo `HCl` are reduced : ` Au(s) + 3H^(+) (aq.) rarr Au^(3+) (aq.) + 3/2 H_2(g) ` But this is not possible because ` E_(Au//Au^(3+))^(Ө) (-1.42 V)` is less than ` E_(H^+//H_(2))^Ө (0.00V)`. In other words, the standard reduction potential of gold is greater than zero . Therefore, the reduced from of gold, i.e., Au (s) is mor stable than the reduced from of hydrogen (i.e., `H_2`) i.e., gold cannot be oxidized by ` H^(+)` ions to give ` H_2`. Hence, gold does not dissolve in ` 1M HCl` solution. Since ` E_(Au^(3+) //Au)^(Ө) (1.42 V)` is greater than ` E_(H^+ //H_2)^Ө` (0.00 V), hydrogen gas passed through the salt solution of gold will reduce auric ions and metallic gold will be percipitated. |
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