#### Electro Chemistry Three Marks Questions

12th Standard EM

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Chemistry

Time : 00:45:00 Hrs
Total Marks : 30
10 x 3 = 30
1. The conductivity of a 0.01M solution of a 1 :1 weak electrolyte at 298K is 1.5$\times$10-4 S cm−1.
i) molar conductivity ozf the solution
ii) degree of dissociation and the dissociation constant of the weak electrolyte
Given that
$\lambda^{0}_{catlon}=248.2\quad S$ cm2 mol-1
$\lambda^{0}_{anlon}=51.8\quad S$ cm2 mol-1

2. Arrange the following solutions in the decreasing order of specific conductance.
i) 0.01M KCl
ii) 0.005M KCl
iii) 0.1M KCl
iv) 0.25 M KCl
v) 0.5 M KCl

3. Why is AC current used instead of DC in measuring the electrolytic conductance?

4. 0.1M NaCl solution is placed in two different cells having cell constant 0.5 and 0.25cm-1 respectively. Which of the two will have greater value of specific conductance.

5. A current of 1.608A is passed through 250 mL of 0.5M solution of copper sulphate for 50 minutes. Calculate the strength of Cu2+ after electrolysis assuming volume to be constant and the current efficiency is 100%.

6. Can Fe3+ oxidises Bromide to bromine under standard conditions?
Given: ${ E }_{ { Fe }^{ 3+ }|{ Fe }^{ 2+ } }^{ 0 }=0.771$
$\\ { E }_{ { Br }_{ 2 }|{ Br }^{ - } }=1.09V$.

7. Is it possible to store copper sulphate in an iron vessel for a long time?
Given : $E^{0}_{Cu^{2+}|Cu} = 0.34$ V and $E^{0}_{Fe^{2+}|Fe} = -0.44$V.

8. Two metals M1 and M2 have reduction potential values of -xV and +yV respectively. Which will liberate H2 and H2SO4.

9. Reduction potential of two metals M1 and M2 are $E^{0}_{M^{2+}_{1}|M_{1}} = -2.3V$ and $E^{0}_{M^{2+}_{1}|M_{1}} = 0.2V$ Predict which one is better for coating the surface of iron. Given: $E^{0}_{Fe^{2+}|Fe} = -0.44$V.

10. A solution of silver nitrate is electrolysed for 20 minutes with a current of 2 amperes. Calculate the mass of silver deposited at the cathode.