1. Which response lists all of the following reactions that are spontaneous unde
ID: 879353 • Letter: 1
Question
1. Which response lists all of the following reactions that are spontaneous under standard electrochemical conditions?
I.
Cr(s) + 3Fe3+ 3Fe2+ + Cr3+
II.
2Fe2+ + Cu2+ 2Fe3+ + Cu
III.
I
II
III
II and III
I and III
2. Which of the following is not a feature of the Nickel Cadmium (Nicad) Cell?
The Nicad cell is a very common secondary cell.
Nickel is oxidized at the anode.
The Nicad cell has a limited number of recharge cycles.
NiO2 is reduced at the cathode.
During discharge, the solid reaction products adhere to the electrodes, allowing the cell to be recharged.
3.Calculate the standard cell potential for the cell, Cd|Cd2+(1 M)||Cu2+(1 M)|Cu.
+0.74 V
0.74 V
+0.06 V
0.06 V
0.00 V
I.
Cr(s) + 3Fe3+ 3Fe2+ + Cr3+
II.
2Fe2+ + Cu2+ 2Fe3+ + Cu
III.
Li(s) + H+ Li+ + H2 (g)
Explanation / Answer
1. Which response lists all of the following reactions that are spontaneous under standard electrochemical conditions?
I. Cr(s) + 3Fe3+ 3Fe2+ + Cr3+
E(Cr3+|Cr) = -0.74V; E(Fe3+|Fe2+) = 0.77V ;
E0cathode = 0.77V: Fe3+ Fe2+
E0anode = -0.74V: Cr3+ Cr(s)
E0cell = E0cathode - E0anode = 0.77-(-0.74)=1.51V; E0cell > 0 ; DG0 = -n*F*E0cell < 0; so spontaneous
II. 2Fe2+ + Cu2+ 2Fe3+ + Cu
E(Cu2+|Cu) = 0.34V ; E(Fe3+|Fe2+) = 0.77V;
E0cathode = 0.34V: Cu2+ Cu
E0anode = 0.77V: Fe3+ Fe2+
E0cell = E0cathode - E0anode = 0.34-(0.77)=-0.43V; E0cell < 0 ; DG0 = -n*F*E0cell > 0; so not spontaneous
III. Li(s) + H+ Li+ + H2 (g)
E(Li+|Li(s)) = -3.05V ; E(H+|H2(g)) = ;
E0cathode = 0V: H+ H2(g)
E0anode = -3.05V: Li+ Li(s)
E0cell = E0cathode - E0anode = 0-(-3.05)= 3.05V; E0cell > 0 ; DG0 = -n*F*E0cell < 0; so spontaneous
Answer is (d) I and III
2. Which of the following is not a feature of the Nickel Cadmium (Nicad) Cell?
Answer is (b) Nickel is oxidized at the anode. Wrong At anode Cadmium is oxidized
The Nicad cell is a very common secondary cell. correct
Nickel is oxidized at the anode. Wrong At anode Cadmium is oxidized
The Nicad cell has a limited number of recharge cycles. correct
NiO2 is reduced at the cathode. Correct
During discharge, the solid reaction products adhere to the electrodes, allowing the cell to be recharged. correct
3.Calculate the standard cell potential for the cell, Cd|Cd2+(1 M)||Cu2+(1 M)|Cu.
E(Cu2+|Cu) = 0.34V ; E(Cd2+|Cd(s)) = -0.4V;
E0cathode = 0.34V: Cu2+ Cu
E0anode = -0.4V: Cd2+ Cd
E0cell = E0cathode - E0anode = 0.34-(-0.4)=0.74V;
Answer is (a) +0.74 V
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