Consider the following E° values


Under standard conditions the potential for the reaction
Sn(s) + 2Fe³⁺(aq) → 2Fe²⁺(aq) + Sn²⁺(aq) is

• 1.68 V

• 0.63 V

• 0.91 V

• 0.91 V

The standard e.m.f of a cell, involving one electron change is found to be 0.591 V at 25°C. The equilibrium constant of the reaction is (F = 96,500 C mol-1: R = 8.314 JK^-1 mol^-1)

• 1.0×10¹

• 1.0×10³⁰

• 1.0×10³⁰

• 1.0×10³⁰

The limiting molar conductivities Λ° for NaCl, KBr and KCl are 126, 152 and 150 S cm² mol^-1 respectively. The Λ° for NaBr is

• 128 S cm² mol^-1

• 302 S cm² mol^-1

• 278 S cm² mol^-1

• 278 S cm² mol^-1

In a cell that utilises the reaction Zn(s) + 2H⁺ (aq) → Zn²⁺(aq) + H₂(g) addition of H₂SO₄ to cathode compartment, will

• lower the E and shift equilibrium to the left

• increases the E and shift equilibrium to the left

• increase the E and shift equilibrium to the right

• increase the E and shift equilibrium to the right

The  values for Cr, Mn, Fe and Co are – 0.41, +1.57, + 0.77 and +1.97 V respectively. For which one of these metals the change in oxidation state form +2 to +3 is easiest?

• Cr

• Co

• Fe

• Fe

How long (approximate) should water be electrolysed by passing through 100 amperes current so that the oxygen released can completely burn 27.66 g of diborane? (Atomic weight of B = 10.8 u)

• 1.6 hours

• 6.4 hours

• 0.8 hours

• 3.2 hours

37.

During electrolysis of molten NaCl, some water was added. What will happen?

• Electrolysis will stop

• Hydrogen will be evolved

• Some amount of caustic soda will be formed

• A fire is likely

The role of fluorspar, which is added in small quantities in the electrolytic reduction of alumina dissolved in fused cryolite is

• as a catalyst

• to make fused mixture conducting

• to lower the melting temperature of the mixture

• to decrease the rate of oxidation of carbon at anode

At temperature of 298K, the emf of the following electrochemical cell,

Ag (s) | Ag⁺ (0.1 M)|| Zn²⁺ (0.1 M) | Zn (s)

will be (Given, E°_cell = -1.562 V)

• -1.532 V

• -1.503 V

• 1.532 V

• -3.06 v

The quantity of electricity needed to separately electrolyze 1 M solution of ZnSO₄ , AlCl3 and AgNO₃ completely is in the ratio of

• 2 : 3 :1

• 2 : 1 : 1

• 2 : 1:3

• 2 : 2 : 1