Zinc is used to protect iron from rusting. This is because

• E${}_{\mathrm{red}}^{°}$ of Zn is greater than that of Fe

• E${}_{\mathrm{ox}}^{°}$ of Zn is greater than that of Fe

• E${}_{\mathrm{red}}^{°}$ of Zn is nearly equal to that of Fe

• Zn is cheap

The standard electrode potential (E°) for OCl^-/ Cl^- and Cl^-/ $\frac{1}{2} {\mathrm{Cl}}_2$ respectively are 0.94 V and -1.36 V. The E° value for OCl^-/ $\frac{1}{2}$Cl₂ will be

• -0.42 V

• -2.20 V

• 0.52 V

• 1.04 V

The electrolyte in lead storage battery is dilute sulphuric, acid. The concentration of sulphuric acid in a lead-storage battery must be between 4.8 M and 5.3 M for most efficient functioning. A 5 mL sulphuric acid sample of a particular battery requires 50 mL of 1.0 M NaOH for complete neutralisation. Which of the following statements about the functioning of battery is the most appropriate?

• The acid concentration in the battery is not in the most effective range

• The acid concentration in the battery is in the most effective range

• The acid concentration in the battery is hardly in the most effective range

• Only a good mechanic can tell whether or not the acid concentration in the battery is in the most effective range

In a cell that utilises the reaction

Zn (s) + 2H⁺ (aq) → Zn²⁺ + H₂ (g)

addition of H₂SO₄ to cathode compartment will

• lower the E and shift equilibrium to the left

• lower the E and shift the equilibrium to the right

• increase the E and shift the equilibrium to the right

• increase the E and shift the equilibrium to the left

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

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

569.

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