An electrochemical cell is shown below Pt, H2(1 atm)| HCI (0.1 M)CH3COOH (0.1 M)|
H2(1 atm), Pt The EMF of the cell will not be zero, because
1. EMF depends on molarities of acids used
2. pH of 0.1 M HCl and 0.1 M CH3COOH is not same
3. the temperature is constant
4. acids used in two compartments are different
Given below are two half-cell reactions:
Mn2+ + 2e- → Mn; E0 = -1.18V
2Mn3+ + 2e- → 2Mn2+; E0 = +1.51V
The E0 for 3Mn2+ → 2Mn+3 + Mn will be:
1. -2.69V; the reaction will not occur
2. -2.69V; the reaction will occur
3. -0.33V; the reaction will not occur
4. -0.33V; the reaction will occur
E0 for Fe2+ + 2e → Fe is –0.44 volt and E0 for Zn2+ + 2e→ Zn is –0.76 volt, thus:
1. Zn is more electropositive than Fe
2. Fe is more electropositive than Zn
3. Zn is more electronegative
4. None of the above
, the standard emf of the reaction
will be
1. 0.111V
2. 0.330V
3. 1.653V
4. 1.212V
The 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:
1. | +0.89 V | 2. | +0.18 V |
3. | +1.83 V | 4. | +1.199 V |
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
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-