81. Electrolysis of $$NaCl$$  solution with inert electrodes for certain period of time gave $$600\,c{m^3}$$  of $$1.0\,M\,NaOH$$   in the electrolytic cell. During the same period $$31.80\,g$$  of copper was deposited in a copper voltmeter in series with the electrolytic cell. What is the percent current efficiency in the electrolytic cell ? $$\left( {At.\,wt.\,{\text{of}}\,Cu = 63.6} \right)$$

A 40
B 25
C 60
D 50
Answer :   60
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82. Given that : $$E_{A{g^ + }/Ag}^ \circ = 0.80\,V\,{\text{and}}\,\left[ {A{g^ + }} \right] = {10^{ - 3}}M;$$         $$E_{Hg_2^{2 + }/Hg}^ \circ = 0.785\,V\,{\text{and}}\,\left[ {Hg_2^{2 + }} \right] = {10^{ - 1}}M$$
which is true for the cell reaction
$$2Hg\left( l \right) + 2A{g^ + }\left( {aq} \right) \to $$     $$2Ag\left( s \right) + Hg_2^{2 + }\left( {aq} \right)?$$

A The forward reaction is spontaneous
B The backward reaction is spontaneous
C $${E_{cell}} = 0.163\,V$$
D $${E_{cell}} = 1.585\,V$$
Answer :   The backward reaction is spontaneous
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83. What will be the reduction potential for the following half-cell reaction at $$298\,K?$$
$$\left( {{\text{Given:}}\left[ {A{g^ + }} \right] = 0.1\,M\,{\text{and}}\,E_{{\text{cell}}}^ \circ = + 0.80\,V} \right)$$

A 0.741 $$V$$
B 0.80 $$V$$
C - 0.80 $$V$$
D - 0.741 $$V$$
Answer :   0.741 $$V$$
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84. The emf of the cell $$Zn\left| {Z{n^{2 + }}\left( {0.01M} \right)} \right|\left| {F{e^{2 + }}\left( {0.001M} \right)} \right|Fe$$         at $$298 K$$  is $$0.2905$$  then the value of equilibrium constant for the cell reaction is

A $${e^{\frac{{0.32}}{{0.0295}}}}$$
B $${10^{\frac{{0.32}}{{0.0295}}}}$$
C $${10^{\frac{{0.26}}{{0.0295}}}}$$
D $${10^{\frac{{0.32}}{{0.0591}}}}$$
Answer :   $${10^{\frac{{0.32}}{{0.0295}}}}$$
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85. During electrolysis of a solution of $$AgN{O_3},$$  9650 coulombs of charge is passed through the solution. What will be the mass of silver deposited on the cathode?

A 108 $$g$$
B 10.8 $$g$$
C 1.08 $$g$$
D 216 $$g$$
Answer :   10.8 $$g$$
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86. What will be the $$emf$$  of the following concentration cell at $${25^ \circ }C?$$
$$A{g_{\left( s \right)}}\left| {AgN{O_3}\left( {0.01\,M} \right)} \right|$$     $$\left| {AgN{O_3}\left( {0.05\,M} \right)} \right|A{g_{\left( s \right)}}$$

A 0.828 $$V$$
B 0.0413 $$V$$
C - 0.0413 $$V$$
D - 0.828 $$V$$
Answer :   0.0413 $$V$$
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87. $$1.08\,g$$  of pure silver was converted into silver nitrate and its solution was taken in a beaker. It was electrolysed using platinum cathode and silver anode. $$0.01$$  Faraday of electricity was passed using $$0.15\,volt$$   above the decomposition potential of silver. The silver content of the beaker after the above shall be

A 0$$\,g$$
B 0.108$$\,g$$
C 1.08$$\,g$$
D None of these
Answer :   0$$\,g$$
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88. On passing a current of $$1.0$$  ampere for $$16\,\min $$  and $$5\,\sec $$  through one litre solution of $$CuC{l_2},$$  all copper of the solution was deposited at cathode. The strength of $$CuC{l_2}$$  solution was ( Molar mass of $$Cu = 63.5;$$   Faraday constant $$ = 96500\,C\,mo{l^{ - 1}})$$

A 0.01$$\,N$$
B 0.01$$\,M$$
C 0.02$$\,M$$
D 0.2$$\,N$$
Answer :   0.01$$\,N$$
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89. Consider the following four electrodes :
$$\eqalign{ & P = C{u^{2 + }}\left( {0.0001\,M} \right)/Cu\left( s \right) \cr & Q = C{u^{2 + }}\left( {0.1\,M} \right)/Cu\left( s \right) \cr & R = C{u^{2 + }}\left( {0.01\,M} \right)/Cu\left( s \right) \cr & S = C{u^{2 + }}\left( {0.001\,M} \right)/Cu\left( s \right) \cr} $$
If the standard reduction potential of $$C{u^{2 + }}/Cu$$   is $$ + 0.34\,V,$$  the reduction potentials in volts of the above electrodes follow the order.

A $$P > S > R > Q$$
B $$S > R > Q > P$$
C $$R > S > Q > P$$
D $$Q > R > S > P$$
Answer :   $$Q > R > S > P$$
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90. Which of the following statements is true?

A When an aqueous solution of $$NaCl$$  is electrolysed, sodium metal is deposited at cathode.
B There is no difference between specific conductivity and molar conductivity.
C Silver nitrate solution can be stored in a copper container.
D The addition of liquid bromine to iodide solution turns it violet.
Answer :   The addition of liquid bromine to iodide solution turns it violet.
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