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Electrochemistry

Short Answer Type

91. What is the effect of an increase in the concentration of zinc ions on the electrode potential of zinc electrode for which E° equals – 0.76 V?

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92. What is a primary cell? Give an example.

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93. Express the relation between conductivity and molar conductivity of a solution.

149 Views

Long Answer Type

94. Explain with examples the terms weak and strong electrolytes. How can these be distinguished?

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95.

Predict the products of electrolysis in each of the following:
(i) An aqueous solution of AgNO₃ with silver electrodes.
(ii) An aqueous solution of AgNO₃ with platinum electrodes.
(iii) A dilute solution of H₂SO₄ with platinum electrodes.
(iv) An aqueous solution of CuCl₂ with platinum electrodes.

174 Views

96.
Depict the galvanic cell in which the reaction
Zn(s) + 2Ag⁺(aq) → Zn²⁺(aq) + 2Ag(s) takes place. Further show:
(i) Which of the electrode is negatively charged?
(ii) The carriers of the current in the cell.
(iii) Individual reaction at each electrode.

The electrochemical cell can be depicted as

(ii) Electrons move from anode (zinc electrode) to cathode (silver electrode) in the external circuit. Zinc ions go into solution at anode and Ag⁺ions get deposited at cathode. Thus electrons in the external and metal ions in the internal circuit act as carrier of current in.
(iii) Overall reaction is obtained by anode and cathode reactions.
Zn(s) + 2Ag⁺(aq) → Zn²⁺(aq) + 2Ag(s)

299 Views

Short Answer Type

97. Following two reactions can occur at cathode in the electrolysis of aqueous sodium chloride:
Na⁺ + e^– → Na(s) 2H₂O(l) + 2r → H₂(g) + 2OH^–(aq)
E°_red = – 0.83 V
Which reaction takes place preferentially and why?

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98. Iron does not rust even if zinc coating is broken in galvanized iron pipe. Explain.

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99. Explain why:
(i) E° for Mn³⁺/ Mn²⁺ couple is more positive than that Fe³⁺/Fe²⁺. (At. No. Mn = 25, Fe = 26).
(ii) Ce³⁺ can be easily oxidised to Ce⁴⁺ (At. No. Ce= 58).

583 Views

100. With the halp of ionic equations describe what happen: When
(i) pH of a solution of dichromate ions is raised.
(ii) Potassium manganate is electro-chemically oxidised.

266 Views