A device that converts energy of the combustion of fuels like hydrogen and methane, directly

into electrical energy is known as:

1. Fuel cell

2. Electrolytic cell

3. Dynamo

4. Ni-Cd cell

Find the compound whose aqueous solution has the highest electrical conductivity.

1. Acetic acid, C₂H₄O₂

2. Hydrochloric acid, HCl

3. Ammonia, NH₃

4. Fructose, C₆H₁₂O₆

The weight of silver (atomic weight = 108) displaced by a quantity of electricity which displaces 5600 mL of O₂ at STP will be : 

1. 5.4 g

2. 10.8 g

3. 54.0 g

4. 108.0 g

At 25° C molar conductance of 0.1 molar aqueous solution of ammonium hydroxide is

9.54 ohm¹cm²mol^-1 and at infinite dilution its molar conductance is 238 ohm¹cm²mol^-1.

The degree of ionisation of ammonium hydroxide at the same concentration and

temperature is

1. 2.080%

2. 20.800%

3. 4.008%

4. 40.800%

A button cell used in watches functions as following

Zn(s) + Ag₂O(s) + H₂O (l) $\rightleftharpoons$2Ag(s) + Zn²⁺(aq) + 2OH^-(aq)

If half cell potentials are

$$\begin{gathered} {{\mathrm{Zn}}^{2+}}_{\left(\mathrm{aq}\right)}<mspace\; width="1em"></mspace>+\hspace{0.17em}2{\mathrm{e}}^{-}<mspace\; width="1em"></mspace>\to <mspace\; width="1em"></mspace>{\mathrm{Zn}}_{\left(\mathrm{x}\right)};<mspace\; width="1em"></mspace>{\mathrm{E}}^{\mathrm{o}}<mspace\; width="1em"></mspace>=<mspace\; width="1em"></mspace>-0.76\mathrm{V} \\ {\mathrm{Ag}}_2{\mathrm{O}}_{\left(\mathrm{s}\right)}<mspace\; width="1em"></mspace>+<mspace\; width="1em"></mspace>{\mathrm{H}}_2{\mathrm{O}}_{\left(\mathrm{l}\right)}<mspace\; width="1em"></mspace>+<mspace\; width="1em"></mspace>2{\mathrm{e}}^{-}<mspace\; width="1em"></mspace>\to <mspace\; width="1em"></mspace>2{\mathrm{Ag}}_{\left(\mathrm{s}\right)}<mspace\; width="1em"></mspace>+<mspace\; width="1em"></mspace>2{{\mathrm{OH}}^{-}}_{\left(\mathrm{aq}\right)};<mspace\; width="1em"></mspace> \\ {\mathrm{E}}^{\mathrm{o}}<mspace\; width="1em"></mspace>=<mspace\; width="1em"></mspace>0.34\mathrm{V} \end{gathered}$$

The cell potential will be

1. 0.84 V

2. 1.34 V

3. 1.10 V

4. 0.42 V

Al₂O₃ is reduced by electrolysis at low potentials and high currents. If 4.5x10⁴ A of

current is passed through molten Al₂O₃ for 6 h,what mass of aluminium is produced ?

(Assume 100% current efficiency, at. mass of Al = 27 g mol^-1)

1. 9.0 x 10³ g

2. 9.1 x 10⁴ g

3. 2.4 x 10⁵ g

4. 1.3 x 10⁴g

Standard free energies of formation (in kJ/mol) at 298 K are -237.2, -394.4 and -8.2 for H₂O(l), CO₂(g) and pentane (g), respectively. The value of E°_cell for the pentane-oxygen fuel cell is

(1) 1.968 V

(2) 2.0968 V

(3) 1.0968 V

(4) 0.0968 V

The efficiency of a fuel cell is given by:

$\left(\mathrm{a}\right)<mspace\; width="1em"></mspace>∆\mathrm{H}/∆\mathrm{G}<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>\left(\mathrm{b}\right)<mspace\; width="1em"></mspace>∆\mathrm{G}/∆\mathrm{S}$
$\left(\mathrm{c}\right)<mspace\; width="1em"></mspace>∆\mathrm{G}/∆\mathrm{H}<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>\left(\mathrm{d}\right)<mspace\; width="1em"></mspace>∆\mathrm{S}/∆\mathrm{G}$

A hypothetical electrochemical cell is shown below A l A⁺ (xM)l l B⁺ (yM) l B
The Emf measured is +0.20 V.The cell reaction is:
1. A⁺ + B → A + B⁺

2.  A⁺ + e^- →  A ; B⁺ + e^- → B

3.  The cell reaction cannot be predicted

4.  A + B⁺ → A⁺ + B

The E° in the given diagram is,

(1) 0.5

(2) 0.6

(3) 0.7

(4) 0.8