Consider the following galvanic cell: Pt, H-2(1.0 atm) | H^+ (1.0 M) || Fe^3+ (0
ID: 980121 • Letter: C
Question
Consider the following galvanic cell: Pt, H-2(1.0 atm) | H^+ (1.0 M) || Fe^3+ (0.010 M), Fe^2+ (0.020 M), Fe^2+ (0.020 M), H^+ (0.1)|Pt For each of the following experiments, will the voltage of the cell increase, decrease, or be unchanged? Addition of 50 mL of 1.0 M HClO_4 to the right half-cell. Addition of some soluble iron(II) salt to the right half-cell. Dissolution of a small amount of potassium permanganate in the right half-cell. An increase in the pressure of hydrogen gas in the left half-cell. A decrease of the pH of the solution in the left half-cell.Explanation / Answer
The nernest equation for above cell reaction is
E= E0 - (2.303RT/nF)log([H+][Fe2+]/[Fe3+])
From the above equation, it may be concluded that by increasing H+ or Fe2+ concentrations the voltage of cell is decreases and by decreasing H+ or Fe2+ concentrations the voltage of cell is increases. In similar, by increasing Fe3+ concentrations the voltage of cell is increases and by decreasing Fe3+ concentrations the voltage of cell is decreases.
(a) By addition of 50 mL 0f 1.0 M HClO4 to the right half cell does decreases the voltage of cell. Because HClO4 is act as a strong oxidizing agent and converts the Fe3+ into Fe2+ and increases the concentartion of Fe2+ and decreases the concentration of Fe3+.
(b) Addition of some soluble iron (II) salt to the right half cell increases the voltage of cell. because the increase in the volume of soluble iron (II) salt decreases the concentaration of Fe2+.
(c)Dissolution of a small amount of potassium permanganate in the right half cell decreases the voltage of cell. Because potassium permanganate is act as a strong oxidizing agent and converts the Fe3+ into Fe2+ and increases the concentartion of Fe2+ and decreases the concentration of Fe3+.
(d) An increase in the pressure of hydrogen gas in the left half cell decreases the volatage of cell. Because, by increasing the pressure of hydrogen its volume decreases which leads to increase in the concentaration of H+
(e) A decrease in the pH of the solution in the left half -cell decrease the voltage of cell. Because decrease in the pH leads to increase in the concentaration of H+.
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