Electrochemistry Test

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Electrochemistry Test - 6

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Weekly Quiz Competition

Question 1
1 / -0

Nernst equation E = E^o - (RT/nF) lnQ indicates that the equilibrium constant K_c will be equal to Q when

A
E = E^o

B
RT/nF = 1

C
E = zero

D
E^o = 1

Solution

Nernst equation E = E^o - (RT/nF) lnQ

At equilibrium: K_c = Q

E = 0

Therefore, E^o = (RT/nF)lnK_c
Question 2
1 / -0

Lead storage battery is an example of

A
secondary cells

B
primary cells

C
fuel cells

D
None of these

Solution

Secondary cells can be recharged by passing electric current and they can be used again and again. The reactions can be reversed by an external electrical energy source. Lead storage battery can be used again and again as they can be charged again after discharging.

A Lead storage battery is the most important type of secondary cell having a lead anode and a grid of lead packed with PbO₂ as cathode. A 38% solution of sulphuric acid is used as electrolyte. (Density=1.294 g mL-1) The battery holds 3.5 L of the acid. During the discharge of the battery, the density of H₂SO₄ falls to 1.139 g mL-1. (20% H₂SO₄by mass)
Question 3
1 / -0

Corrosion of iron may be prevented by

A
covering the surface of iron with metallic nickel by electroplating

B
keeping the surface of iron wet

C
keeping a copper block in contact with iron

D
keeping iron immersed in brine

Solution

Iron corrodes when it is in contact with air and moisture for. Presence of electrolytes like salt in water increases the rate of corrosion. Iron objects are electroplated with Nickel, which prevents iron it from coming in contact with these and Nickel itself does not corrode in air or moisture.

Hence, option (1) is correct.
Question 4
1 / -0

An electrochemical cell is represented as follows.

Pt (H₂, 1 atm) | 0.1 M HCl || 0.1 M acetic acid | (H₂, 1 atm) Pt

The emf of this cell will not be zero because the

A
pH values of 0.1 M HCl and 0.1 M acetic acid are not the same

B
acids used in two compartments are different

C
emf of a cell depends on the molarities of acids used

D
temperature is constant

Solution

The emf of this cell will not be zero because the pH values of 0.1 M HCl and 0.1 M acetic acid are not the same.
Question 5
1 / -0

Electrolysis of dilute aqueous NaCl solution was carried out by passing 100-milli ampere current. The time required to liberate 0.05 mol of H₂ gas at the cathode is (1 Faraday = 96500 C mol⁻¹)

A
9.65 × 10⁴ sec

B
19.30 × 10⁴ sec

C
28.95 × 10⁴ sec

D
38.6 × 10⁴ sec

Solution

Q = i × t

Q = 100 × 10⁻³ × t

2H₂O + 2e⁻ → H₂ + 2OH⁻

To liberate 0.05 mole of H₂, 0.1 Faraday charge is required.

Q = 0.1 × 96500 C

∴ 0.1 × 96500 = 10^-1 × t

t = 9.65 × 10⁴ sec

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Electrochemistry Test - 6

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Electrochemistry Test - 6

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Question 1

E = Eo

RT/nF = 1

E = zero

Eo = 1

Solution

Question 2

secondary cells

primary cells

fuel cells

None of these

Solution

Question 3

covering the surface of iron with metallic nickel by electroplating

keeping the surface of iron wet

keeping a copper block in contact with iron

keeping iron immersed in brine

Solution

Question 4

pH values of 0.1 M HCl and 0.1 M acetic acid are not the same

acids used in two compartments are different

emf of a cell depends on the molarities of acids used

temperature is constant

Solution

Question 5

9.65 × 104 sec

19.30 × 104 sec

28.95 × 104 sec

38.6 × 104 sec

Solution

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E = E^o

E^o = 1

9.65 × 10⁴ sec

19.30 × 10⁴ sec

28.95 × 10⁴ sec

38.6 × 10⁴ sec