Electrochemistry · JEE Main previous year questions

2012 3 questions

1. Q742012 · 26 May 2012 · Shift 1

   Given ${\mathrm{E}}_{\mathrm{C}{\mathrm{u}}^{2+}/Cu}^{\circ }=0.34\mathrm{V},{\mathrm{E}}_{\mathrm{C}{\mathrm{u}}^{2+}/C{\mathrm{u}}^{+}}^{\circ }=0.15\mathrm{V}$ Standard electrode potential for the half cell $\mathrm{C}{\mathrm{u}}^{+}/Cu$ is

   1. A.$0.38\mathrm{V}$
   2. B.$0.53\mathrm{V}$
   3. C.$0.19\mathrm{V}$
   4. D.$0.49\mathrm{V}$
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   Answer: B

2. Q882012 · 12 May 2012 · Shift 1

   In the electrolysis of alumina to obtain aluminium metal, cryolite is added mainly to

   1. A.lower the melting point of alumina
   2. B.dissolve alumina in molten cryolite
   3. C.remove the impurities of alumina
   4. D.increase the electrical conductivity
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   Answer: A

3. Q722012 · 7 May 2012 · Shift 1

   A battery is constructed of Cr and $\mathrm{N}{\mathrm{a}}_2\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_7$. The unbalanced chemical equation when such a battery discharges is following: $$\mathrm{N}{\mathrm{a}}_2\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_7+\mathrm{Cr}+{\mathrm{H}}^{+}\to \mathrm{C}{\mathrm{r}}^{3+}+{\mathrm{H}}_2\mathrm{O}+\mathrm{N}{\mathrm{a}}^{+}$$ If one Faraday of electricity is passed through the battery during the charging, the number of moles of $\mathrm{C}{\mathrm{r}}^{3+}$ removed from the solution is

   1. A.$\frac{4}{3}$
   2. B.$\frac{1}{3}$
   3. C.$\frac{3}{3}$
   4. D.$\frac{2}{3}$
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   Answer: D