Standard electrode potential for Sn4+/Sn2+
couple is + 0.15 V and that for the Cr3+/Cr couple is 0.74 V. These two couples in their standard state are
connected to make a cell. The cell potential will be
(A)
+ 1.19 V
(B)
+ 0.89 V
(C)
+ 0.18 V
(D)
+ 1.83 V
Correct Answer is Option (B)
E°Sn4+/Sn2+ = 0.15 V
E°Cr3+/Cr = –0.74 V
E°cell = E°cathode – E°anode
= 0.15 – (– 0.74) = 0.15 + 0.74 = 0.89 V
10. ⇒(AIPMT 2010 Mains
)
Consider the following relations for emf of an electrochemical cell
(i) EMF of cell = (Oxidation potential of anode) (Reduction potential of cathode)
(ii) EMF of cell = (Oxidation potential of anode) + (Reduction potential of cathode)
(iii) EMF of cell = (Reductional potential of anode) + (Reduction potential of cathode)
(iv) EMF of cell = (Oxidation potential of anode) (Oxidation potential of cathode)
Which of the above relations are correct?
(A) (iii) and (i)
(B) (i) and (ii)
(C) (iii) and (iv)
(D) (ii) and (iv)
Correct Answer is Option (D)
EMF of a cell = Reduction potential of cathode
– Reduction potential of anode
= Reduction potential of cathode +
Oxidation potential of anode
= Oxidation potential of anode –
Oxidation potential of cathode.
11. ⇒(AIPMT 2008
)
On the basis of the following Eo values, the strongest
oxidizing agent is
[Fe(CN)6]4 [Fe(CN)6]3 + e; Eo = 0.35 V
Fe2+ Fe3+ + e; Eo = 0.77 V
(A)
Fe3+
(B)
[Fe(CN)6]3
(C)
[Fe(CN)6]4
(D)
Fe2+
Correct Answer is Option (A)
Substances which have higher reduction
potential are stronger oxidizing agent.
[Fe(CN)6]4 [Fe(CN)6]3 + e; Eo = 0.35 V
Fe2+ Fe3+ + e; Eo = 0.77 V
Higher the +ve reduction potential, stronger will
be the oxidising agent. Oxidising agent oxidises
other compounds and gets itself reduced easily.
12. ⇒(AIPMT 2006
)
EoFe2+/Fe = 0.441 V and
EoFe3+/Fe2+ = 0.771 V, the standard EMF of the reaction Fe +
2Fe3+ 3Fe2+ will be
(A)
0.111 V
(B)
0.330 V
(C)
1.653 V
(D)
1.212 V
Correct Answer is Option (D)
At anode : Fe Fe2+ + 2e-; Eo
=
-0.441
V
At cathode : Fe3+ + e– Fe2+; Eo = 0.771 V
Fe + 2Fe3+ 3Fe2+; Eo = ?
To get the above equation, (ii) × 2 – (i)
2Fe3+ + 2e– 2Fe2+; Eo = 0.771 V
Fe Fe2+ + 2e-; Eo
= -
0.441 V
------------------------------------------------
Fe + 2Fe3+ 3Fe2+
Eo = 0.771 + 0.441 = 1.212 V
13. ⇒(AIPMT 2006
)
A hypothetical electrochemical cell is shown below.
The emf measured is + 0.20 V. The cell reaction is
(A)
A + B+ A+ + B
(B)
A+ + B A + B+
(C)
A+ + e A; B+ + e B
(D) the cell reaction cannot be predicted.
Correct Answer is Option (A)
From the given expression:
At anode : A A+
+ e–
At cathode : B+
+ e– B
Overall reaction is : A + B+ A+
+ B
14. ⇒(AIPMT 2001
)
Standard electrode potentials are Fe2+/Fe
[Eo = 0.44] and Fe3+/Fe2+[
Eo = 0.77]; If Fe2+, Fe3+ and Fe blocks are kept together, then
(A)
Fe3+ increases
(B)
Fe3+ decreases
(C)
Fe2+/Fe3+ remains unchanged
(D)
Fe2+ decreases.
Correct Answer is Option (B)
The metals having higher negative values
of their electrode potential can displace metals
having lower values from their salt solutions.