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Electrochemistry

Long Answer Type

121. Define the terms equivalent and molar conductivity. What are their physical signific-ance?

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Short Answer Type

122. How is molar conductivity related to concentration of an electrolyte? How will you explain a weak and a strong electrolyte based on their conductivity values?

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123. What is corrosion? What are the factors which effect corrosions? CO₂ is always present in natural water. Explain its affect (increases, stops or no effect > on rusting of Fe.)

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124. What is a salt bridge? What is its significance?

186 Views

Long Answer Type

125.

What is corrosion? Describe the electrochemical phenomenon of rusting of iron.

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126. Explain why electrolysis of aqueous solution of NaCl gives H₂ at cathode and Cl₂ at anode. Write overall reaction.

Sodium chloride and water ionize as follows:

At cathode: Both Na⁺ and H⁺ ions are present near the cathode. But the discharge potential of H⁺ is lower than that of Na⁺ ion. So H⁺ ions are discharged in preference to Na⁺ ions.

Thus H₂ gas is liberated at the cathode and Na⁺ ions remain in the solution.
At the anode: Both Cl^– and OH^– ions are present near the anode. As the discharge potential of Cl^– ions is lower than that of oh" ions, so Cl^– ions are discharged in presence to OH^– ions.

Thus Cl₂ is liberated at anode and OH^– ions remain in the solution.
The overall reaction is:
NaCl(aq) + H₂ O(l) → Na⁺ (aq) + OH^–(aq)

plus 1 half straight H subscript 2 left parenthesis straight g right parenthesis plus 1 half Cl subscript 2 left parenthesis straight g right parenthesis

3952 Views

Short Answer Type

127.

The following curve is obtained when molar conductivity λ_m (y-axis) is plotted against the square root of concentration C^1/2 (x-axis) for two electrolytes A and B.
(a) What can you about the nature of the two electrolytes A and B.
(b) How do you account for the increase in molar conductivity λ_m for the electrolytes A and B on dilution.

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128. How is the standard free energy change related to
(i) emf of a galvanic cell related to the reaction.
(ii) equilibrium constant of the reaction in equilibrium state?

135 Views