The standard reduction potential at 290 K for the following half reactions are,
(i) Zn2+ + 2e— → Zn(s); E° = -0.762 V
(ii) Cr3+ + 3e → Cr(s); E° = -0.740 V
(iii) 2H+ + 2e → H2(g); · E° = +0.000 V
(iv) Fe3+ + e → Fe2+; E° = +0.77V
Which is the strongest reducing agent?
1. Zn
2. Cr
3. Fe2+
4. H2
Which graph correctly correlates Ecell as a function of concentrations for the cell (for different values of M and M') ?
1. 2.
3. 4.
The most convenient method to protect the bottom of the ship made of iron is
1. coating it with red lead oxide
2. white tin plating
3. connecting it with Mg block
4. connecting it with Pb block
The electrode potentials for
are +0.15 V and +0.50 V respectively. The value of will be
1. 0.325 V
2. 0.650 V
3. 0.150 V
4. 0.500 V
The Zn acts as sacrificial or cathodic protection to prevent rusting of iron because:
1. of Zn < of Fe
2. of Zn > of Fe
3. of Zn = of fe
4. Zn is cheaper than iron
The standard reduction potential for Fe2+|Fe and Sn2+|Sn electrodes are -0.44 V and -0.14 V respectively. For the cell reaction,
Fe2+ + Sn → Fe + Sn2+, the standard Emf is -
1. +0.30 V
2. 0.58 V
3. +0.58 V
4. -0.30 V
On electrolysing a solution of dilute H2SO4 between platinum electrodes, the gas evolved at the anode and cathode are respectively:
1. SO2 and O2
2. SO3 and H2
3. O2 and H2
4. H2 and O2
In electrolysis of NaCl when Pt electrode is taken then H2 is liberated at cathode while with Hg cathode it forms sodium amalgam because :
1. Hg is more inert than Pt
2. More voltage is required to reduce H+ at Hg than at Pt
3. Na is dissolved in Hg while it does not dissolve in Pt
4. Concentration of H+ ions is larger when Pt electrode is taken.
If mercury is used as cathode in the electrolysis of aqueous NaCl solution, the ions discharged at cathode are:
1. H+
2. Na+
3. OH-
4. Cl-
Standard Reduction electrode potential of three metals X, Y, and Z are -1.2 V, +0.5 V and -3 V respectively. The reducing power of these metals will be :
1. | Y > X >Z | 2. | Z > X > Y |
3. | X > Y > Z | 4. | Y > Z > X |