Which of the following reaction is used to make a fuel cell?

• Cd (s) + 2Ni(OH)₃ (s) → CdO (s) + 2Ni(OH)₂ (s) + H₂O (l)

• 2Fe (s) + O₂ (g) + 4H⁺ (aq) → 2Fe²⁺ (aq) + 2H₂O (l)

• Pb (s) + PbO₂ (s) + 2H₂SO₄ (aq) → 2PbSO₄ (s) + 2H₂O (l)

• 2H₂ (g) + O₂ (g) → 2H₂O (l)

Given the following in Eq. (i) and (ii), calculate the EMF of the cell given in Eq. (iii)

CuI(s) + e^- → Cu(s) + I^-  E°= -0.16    ...(i)

Zn²⁺(aq) + 2e^-  →  Zn(s)  E°= -0.76  ...(ii)

Zn| Zn²⁺(1.0M) || I^-(1.0M)|CuI|Cu ... (iii)

• 1.08V

• 0.44V

• 0.92V

• 0.60V

When the sample of copper with zinc impurity is to be purified by electrolysis, the appropriate electrodes are

•  

  Anode	Cathode
  Pure zinc	pure copper

•  

  Anode	Cathode
  impure zinc	pure copper

•  

  Anode	Cathode
  impure zinc	impure sample

•  

  Anode	Cathode
  impure sample	pure copper

234.

One faraday of current was passed through the electrolytic cells placed in series containing solution of Ag⁺, Ni²⁺ and Cr³⁺ respectively. The ratio of amounts of Ag, Ni and Cr deposited will be

(atomic weigth of Ag = 108, Ni = 59 and Cr = 52)

• 108, 29.5, 17.4

• 17.4, 29.5, 108

• 1, 2, 3

• 108, 59, 52

Zinc is used to protect iron from corrosion because

• E_red of An < E_red of iron

• E_oxidation of Zn < E_oxidation of iron

• E_oxidation of Zn = E_oxidation of iron

• Zinc is cheaper than iron

Which of the following is correct increasing order for the value of $\frac{\mathrm{e}}{\mathrm{m}}$ ?

• e < p < n < α

• n < p < e < α

• n < p < α < e

• n < α < p < e

If an element A is placed in an electrochemical series above element B but below element C, then the order of oxidation power of elements is

• C>A>B

• B>A>C

• A>B>C

• C>B>A

Given, ${\mathrm{E}}_{{\mathrm{Cr}}^{3+}/ \mathrm{Cr}}^{°} = -0.72 \mathrm{V}, {\mathrm{E}}_{{\mathrm{Fe}}^{2+}/ \mathrm{Fe}}^{°} = -0.42 \mathrm{V}.$The potential for the cell Cr | Cr³⁺ (0.1 M) || Fe²⁺ (0.01 M) | Fe is

• 0.26 V

• 0.399 V

• -0.399 V

• -0.26 V

A lead storage battery is discharged. During the charging of this battery, the reaction that occurs at anode, is

• ${\mathrm{PbSO}}_4 \left(\mathrm{s}\right) + 2{\mathrm{e}}^{-} \to \mathrm{Pb}\left(\mathrm{s}\right) +\hspace{0.17em}{\mathrm{SO}}_4^{2-}\left(\mathrm{aq}\right)$

• ${\mathrm{PbSO}}_4 \left(\mathrm{s}\right) + 2{\mathrm{H}}_2\mathrm{O} \to {\mathrm{PbO}}_2\left(\mathrm{s}\right) +\hspace{0.17em}{\mathrm{SO}}_4^{2-}\left(\mathrm{aq}\right)+ 4{\mathrm{H}}^{+}\left(\mathrm{aq}\right) + 2{\mathrm{e}}^{-}$

• ${\mathrm{PbSO}}_4 \left(\mathrm{s}\right) \to {\mathrm{Pb}}^{2+}\left(\mathrm{aq}\right) +\hspace{0.17em}{\mathrm{SO}}_4^{2-}\left(\mathrm{aq}\right)$

• ${\mathrm{PbSO}}_4 \left(\mathrm{s}\right) +2{\mathrm{H}}_2\mathrm{O} + 2{\mathrm{e}}^{-} \to {\mathrm{PbO}}_2\left(\mathrm{s}\right) +\hspace{0.17em}{\mathrm{SO}}_4^{2-}\left(\mathrm{aq}\right)+ 2{\mathrm{H}}^{+}\left(\mathrm{aq}\right)$

Which one of the following is correct plot of Λ_m ( in S cm² mol^-1) and √C (in mol/L^1/2) for KCl solution? ( y= Λ_m; x= √C)