TIWARI CHEMISTRY CLASSES
CHEMISTRY TEST
CLASS XII (ELECTROCHEMISTRY )
TIME ; 45MIN M.M =25
1. State Kohlrausch law of independent migration of ions. [1]
2. Explain the variation in molar conductivity of strong electrolytes with change of concentration. [2]
3 Define conductivity and molar conductivity for the solution of an electrolyte. [2]
4. What are fuel cells? Write the electrode reactions and overall reaction of H2-O2 fuel cell. [2]
5. What type of battery is the lead storage battery? Write the anode and cathode reactions and [2]
overall reaction occurring in a lead storage battery when current is drawn from it. What
happens on charging the battery?
6. Write the Nernst equation and calculate the emf and ΔG of the following cell at 298 K : [3]
2+ -4
Cu(s)│Cu (0.130 M)║Ag+ (1x10 M)│Ag(s)
Given : E0Cu2+/Cu = 0.34 V, E0Ag+/Ag = +0.80 V
7. (a) Calculate the degree of dissociation (α) and dissociation constant of acetic acid if its molar [2]
Conductivity. (∧m) is 39.05 S cm2mol–1. Given λo(H+) = 349.6 S cm2 mol–1 and
λo(CH3COO–) = 40.9 S cm2 mol–1
(b) Calculate the mass of Ag deposited at cathode when a current of 2 amperes was passed through a
solution of AgNO3 for 15 minutes. Given : Molar mass of Ag = 108 g mol–1
1F = 96500 C mol–1) [2]
8 Given that the standard electrode potentials (E°) of metals are :
K+/K = -2.93 V, Ag+/Ag = 0.80 V, Cu2+/Cu = 0.34 V, Mg2+/Mg = -2.37 V, Cr3+/Cr = -0.74 V,
Fe2+/Fe = -0.44 V. Arrange these metals in increasing order of their reducing power. [1]
TIWARI CHEMISTRY CLASSES
CHEMISTRY TEST
CLASS XII (ELECTROCHEMISTRY )
TIME ; 45MIN M.M =25
1. State Kohlrausch law of independent migration of ions. [1]
2. Explain the variation in molar conductivity of strong electrolytes with change of concentration. [2]
3 Define conductivity and molar conductivity for the solution of an electrolyte. [2]
4. What are fuel cells? Write the electrode reactions and overall reaction of H2-O2 fuel cell. [2]
5. What type of battery is the lead storage battery? Write the anode and cathode reactions and [2]
overall reaction occurring in a lead storage battery when current is drawn from it. What
happens on charging the battery?
6. Write the Nernst equation and calculate the emf and ΔG of the following cell at 298 K : [3]
2+
Cu(s)│Cu (0.130 M)║Ag+ (1x10-4 M)│Ag(s)
Given : E0Cu2+/Cu = 0.34 V, E0Ag+/Ag = +0.80 V
7. (a)Calculate the degree of dissociation (α) and dissociation constant of acetic acid if its molar [2]
2 –1 o + 2 –1
Conductivity. (∧m) is 39.05 S cm mol . Given λ (H ) = 349.6 S cm mol and
λ (CH3COO–) = 40.9 S cm2 mol–1
o
(b) Calculate the mass of Ag deposited at cathode when a current of 2 amperes was passed through a
solution of AgNO3 for 15 minutes. Given : Molar mass of Ag = 108 g mol–1
1F = 96500 C mol–1) [2]
8 Given that the standard electrode potentials (E°) of metals are :
K+/K = -2.93 V, Ag+/Ag = 0.80 V, Cu2+/Cu = 0.34 V, Mg2+/Mg = -2.37 V, Cr3+/Cr = -0.74 V,
Fe2+/Fe = -0.44 V. Arrange these metals in increasing order of their reducing power. [1]
9. (a) When a bright silver object is placed in the solution of gold chloride, it acquires a golden tinge
but nothing happens when it is placed in a solution of copper chloride. Explain this behaviour of
silver. [Given : E0 Cu2+/Cu = +0.34V, E0Ag+/Ag = +0.80V, E0Au3+/Au = +1.40V] [2]
(b) A voltaic cell is set up at 25 °C with the following half cells:
Al/Al3+(0.001 M) and Ni/Ni2+(0.50 M)
Write an equation for the reaction that occurs when the cell generates an electric current and
determine the cell potential. [E0 Ni2+/Ni= -0.25 V and E0Al3+/Al = – 1.66 V] , [3]
[log 4 = 0.6021 log 3 = 0.4771 log 2 = 0.3010 log 10 = 1 log8=0.9030 ]
10 .At 298 K, molar conductivity at infinite dilution of NH4Cl, NaOH and NaCl are 129.8, 217.4
and 108.9 S cm2 mol-1 respectively. If the molar conductivity of centimolar solution of NH4OH is
9.33 S cm2 mol-1, what is the percentage dissociation of NH4OH at this dilution? Also calculate the
dissociation constant of NH4OH. [3]
9. (a) When a bright silver object is placed in the solution of gold chloride, it acquires a golden tinge
but nothing happens when it is placed in a solution of copper chloride. Explain this behaviour of
silver. [Given : E0 Cu2+/Cu = +0.34V, E0Ag+/Ag = +0.80V, E0Au3+/Au = +1.40V] [2]
(b) A voltaic cell is set up at 25 °C with the following half cells:
Al/Al3+(0.001 M) and Ni/Ni2+(0.50 M)
Write an equation for the reaction that occurs when the cell generates an electric current and
determine the cell potential. [E0 Ni2+/Ni= -0.25 V and E0Al3+/Al = – 1.66 V] , [3]
[log 4 = 0.6021 log 3 = 0.4771 log 2 = 0.3010 log 10 = 1 log8=0.9030 ]
10 .At 298 K, molar conductivity at infinite dilution of NH4Cl, NaOH and NaCl are 129.8, 217.4
and 108.9 S cm2 mol-1 respectively. If the molar conductivity of centimolar solution of NH4OH is
9.33 S cm2 mol-1, what is the percentage dissociation of NH4OH at this dilution? Also calculate the
dissociation constant of NH4OH. [2]
