During electrolysis of molten NaCl, some water was added. What will happen?

• Electrolysis will stop

• Hydrogen will be evolved

• Some amount of caustic soda will be formed

• A fire is likely

The role of fluorspar, which is added in small quantities in the electrolytic reduction of alumina dissolved in fused cryolite is

• as a catalyst

• to make fused mixture conducting

• to lower the melting temperature of the mixture

• to decrease the rate of oxidation of carbon at anode

At temperature of 298K, the emf of the following electrochemical cell,

Ag (s) | Ag⁺ (0.1 M)|| Zn²⁺ (0.1 M) | Zn (s)

will be (Given, E°_cell = -1.562 V)

• -1.532 V

• -1.503 V

• 1.532 V

• -3.06 v

The quantity of electricity needed to separately electrolyze 1 M solution of ZnSO₄ , AlCl3 and AgNO₃ completely is in the ratio of

• 2 : 3 :1

• 2 : 1 : 1

• 2 : 1:3

• 2 : 2 : 1

The two half-cell reactions of an electrochemical cell is given as

$$\begin{gathered} {\mathrm{Ag}}^{+} + {\mathrm{e}}^{-} \to \mathrm{Ag}; \mathrm{E}{°}_{{\mathrm{Ag}}^{+}/\mathrm{Ag}}=-0.3995 \mathrm{V} \\ {\mathrm{Fe}}^{2+}\to {\mathrm{Fe}}^{3+} + {\mathrm{e}}^{-} ; \mathrm{E}{°}_{{\mathrm{Fe}}^{3+} /{\mathrm{Fe}}^{2+}}= -0.7120 \mathrm{V} \end{gathered}$$

The value of cell EMF will be

• -0.3125 V

• 0.3125 V

• 1.114 V

• -1.114V

At 25C, the molar conductance of 0.007 M hydrofluoric acid is 150 mho cm²mol^-1and its $\mathrm{\lambda }{°}_{\mathrm{m}}$ = 500 mho cm²mol^-1. The value of the dissociation constant of the acid at the given concentration at 25°C is

• 7 X 10^-4 M

• 7 X 10^-5 M

• 9 X 10^-3 M

• 9 X 10^-4 M

The formal potential of Fe³⁺ /Fe⁴⁺ in a sulphuric acid and phosphoric acid mixture (E° = + 0.61 V) is much lower than the standard potential (E° = + 0. 77 V). This is due to

• formation of the species [FeHPO₄]⁺

• lowering of potential upon complexation

• formation of the species [FeSO₄]⁺

• high acidity of the medium

A conductivity cell has been calibrated with a 0.01 M 1 : 1 electrolyte solution (specific conductance, k = 1.25 × 10^-3S cm^-1) in the cell and the measured resistance was 800 $\Omega$ at 25°C. The cell constant will be

• 1.02 cm^-1

• 0.102 cm^-1

• 1.00 cm^-1

• 0.5 cm^-1

Equivalent conductivity at infinite dilution for sodium-potassium oxalate [(COO^-)₂ Na⁺K⁺] will be [given molar conductivities of oxalate, K⁺ and Na⁺ ions at infinite dilution are 148.2, 50.1, 73.5 S cm mol' respectively]

• 271.8 S cm² eq^-1

• 67.95 S cm² eq^-1

• 543.6 S cm² eq^-1

• 135.9 S cm² eq^-1

The standard reduction potential E° for half-reaction are

Zn → Zn²⁺ + 2e^- ; E° = + 0.76 V

 Fe → Fe²⁺ + 2e^- ; E° = + 0.41 V

The EMF of the cell reaction

Fe²⁺ + Zn → Zn²⁺ + Fe is

• -0.35 V

• +0.35 V

• +1.17 V

• -1.17 V