22258.The oxidation state of chromium in the final product formed by the reaction between Kl and acidified potassium dichromate solution is
+6
+4
+3
+2
22259.Resistance of 0.2 M solution of an electrolyte is 50 Ω. The specific conductance of the solution is 1.3 S m–1. If resistance of the 0.4 M solution of the same electrolyte is 260 Ω, its molar conductivity is
62.5 S m2 mol–1
6250 S m2 mol–1
6.25 × 10–4 S m2 mol–1
625 × 10–4 S m2 mol–1
22260.E1, E2 and E3 are the emf values of the three galvanic cells respectively.
(a) Zn | Zn+2
1 M || Cu+2
0.1 M | Cu
(b) Zn | Zn+2
1 M || Cu+2
1 M | Cu
(c) Zn | Zn+2
0.1 M || Cu+2
1 M | Cu
Which one of the following is true?
E2 > E3 > E1
E3 > E2 > E1
E1 > E2 > E3
E1 > E3 > E2
22261.Which among the following metals is employed to provide cathodic protection to iron?
Zinc
Nickel
Tin
Lead
22262.The equivalent conductance of M/32 solution of a weak monobasic acid is 8.0 mhos cm2 and at infinite dilution is 400 mhos cm2. The dissociation constant of this acid is
1.25 × 10–6
6.25 × 10–4
1.25 × 10–4
1.25 × 10–5
22263.The standard emf of galvanic cell involving 3 moles of electrons in its redox reaction is 0.59 V. The equilibrium constant for the reaction of the cell is
1025
1020
1015
1030
22264.9.65 C of electric current is passed through fused anhydrous magnesium chloride. The magnesium metal thus, obtained is completely converted into a Grignard reagent. The number of moles of the Grignard reagent obtained is ______.
5 × 10–4
1 × 10–4
5 × 10–5
1 × 10–5
22265.An increase in equivalent conductance of a strong electrolyte with dilution is mainly due to
increase in both i.e. number of ions and ionic mobility of ions.
increase in number of ions
increase in ionic mobility of ions
100% ionization of electrolyte at normal dilution
22266.The Gibbs energy for the decomposition of Al2O3 at 500°C is as follows:
$\dfrac{2}{3}$Al2O3 → $\dfrac{4}{3}$Al + O2, ΔrG = +966 kJ mol–1
The potential difference needed for electrolytic reduction of Al2O3 at 500°C is at least
2.5 V
5.0 V
4.5 V
3.0 V
22267.Resistance of a conductivity cell filled with a solution of an electrolyte of concentration 0.1 M is 100 Ω. The conductivity of this solution is 1.29 S m–1. Resistance of the same cell when filled with 0.2 M of the same solution is 520 Ω. The molar conductivity of 0.02 M solution of the electrolyte will be
124 × 10–4 S m2 mol–1
1240 × 10–4 S m2 mol–1
1.24 × 10–4 S m2 mol–1
12.4 × 10–4 S m2 mol–1
22268.The highest electrical conductivity of the following aqueous solutions is of
0.1 M acetic acid
0.1 M chloroacetic acid
0.1 M fluoroacetic acid
0.1 M difluoroacetic acid
22269.The equivalent conductivity of 0.1 M weak acid is 100 times less than that at infinite dilution. The degree of dissociation is
100
10
0.01
0.001
22270.Saturated solution of KNO3 is used to make 'salt bridge' because
velocity of K+ is greater than that of NO–
3
3
velocity of NO–
3 is greater than that of K+
3 is greater than that of K+
velocity of both K+ and NO–
3 are nearly the same
3 are nearly the same
KNO3 is highly soluble in water
22271.Which of the following complexes has lowest molar conductance?
CoCl3 · 3NH3
CoCl3 · 4NH3
CoCl3 · 5NH3
CoCl3 · 6NH3
22272.For the electrochemical cell:
M | M+ || X– | X, E° [ M+ | M ] = 0.44 V and E° [ X | X– ] = 0.33 V.
From the data one can deduce that
M + X → M+ + X– is the spontaneous reaction
M+ + X– → M + X is the spontaneous reaction
Ecell = 0.77 V
Ecell = –0.77 V
22273.Li occupies higher position in the electrochemical series of metals as compared to Cu since
the standard reduction potential of Li+/Li is lower than that of Cu2+/Cu
the standard reduction potential of Cu2+/Cu is lower than that of Li+/Li
the standard oxidation potential of Li/Li+ is lower than that of Cu/Cu2+
Li is smaller in size as compared to Cu
22274.What is the quantity of electricity (in coulombs) required to deposit all the silver from 250ml of 1 M AgNO3 solution? (Ag = 108)
2412.5
24125
4825.0
48250
22275.The standard reduction potential E° for half reactions are
Zn = Zn2+ + 2e– E° = +0.76 V
Fe = Fe2+ + 2e– E° = + 0.41 V
The EMF of the cell reaction Fe2+ + Zn = Zn2+ + Fe is
– 0.35 V
+ 0.35
+ 1.17 V
– 1.17 V
22276.The rusting of iron takes place as follows
2H+ + 2e– + $\dfrac{1}{2}$O2 → H2O(l); E° = +1.23 V
Fe2+ + 2e– → Fe(s); E° = –0.44 V
Calculate ΔG° for the net process
–322 kJ mol–1
–161 kJ mol–1
–152 kJ mol–1
–76 kJ mol–1
22277.The reduction potential of hydrogen half–cell will be negative if:
p(H2) = 2 atm and [H+] = 2.0 M
p(H2) = 1 atm and [H+] = 2.0 M
p(H2) = 1 atm and [H+] = 1.0 M
p(H2) = 2 atm and [H+] = 1.0 M