EMF

Q.

The value of enthalpy change $\Delta H$ for the reaction

$C_2{H}_{5}OH\left(1\right)+3O_2\left(g\right)\to 2C{O}_2\left(g\right)+3H_{2}O\left(1\right)at{27}^{\circ }Cis-1366.5kJmo{l}^{-1},$ The value of internal

energy change for the above reaction at this temperature will be:

1. -1364.0 kJ

2. -1361.5 kJ

3. -1371.5 kJ

4. -1369 kJ

Q. Half cell reactions for some electrodes are given below A +e- --> A+ E⁰=0.96V B- +e- --> B²- E⁰=-0.12V C+ +e- --> C E⁰=+0.18V D²+ +e- --> D E⁰=-1.12V Construct a cell which can produce largest potential

Q. Which of the following statement is not correct for a dry cell battery?

1. Carbon(graphite) rod will act as cathode
2. Ammonia produced in the cell reaction will forms a complex with $Z{n}^{2+}$
3. Cell reaction will be reversed while passing current
4. Zinc metal will act as a anode

Q. Given below are the half - cell reactions
$M{n}^{2+}+2e^{-}\to Mn;E^{\circ }=-1.18eV$
$2(M{n}^{3+}+e^{-}\to M{n}^{2+});E^0=+1.51eV$
The $E^{\circ }$for $3M{n}^{2+}\to Mn+2M{n}^{3+}$ will be

1. -2.69 V; the reaction will not occur
2. -2.69 V; the reaction will occur
3. -0.33 V; the reaction will not occur
4. -0.33 V; the reaction will occur

Q. Electromotive force (EMF) is the potential difference when the circuit is open.

1. True
2. False

Q. Which of the following represent the correct expressions to calculate reduction potential of the following half cells at $25{}^{o}C$.
$C{l}^{-}\left(aq\right)|C{l}_2(g,1atm)|Pt\left(s\right)$

1. $E_{C{l}_2/C{l}^{-}}=E_{C{l}_2/C{l}^{-}}^0-0.059log\frac{1}{\left[C{l}^{-}\right]}$
2. $E_{C{l}_2/C{l}^{-}}=E_{C{l}_2/C{l}^{-}}^0+0.059log\left[C{l}^{-}\right]$
3. $E_{C{l}_2/C{l}^{-}}=E_{C{l}_2/C{l}^{-}}^0-0.059log\left[C{l}^{-}\right]$
4. $E_{C{l}_2/C{l}^{-}}=E_{C{l}_2/C{l}^{-}}^0-\frac{0.059}{2}log\left[C{l}^{-}\right]$

Q. In a hydrogen-oxygen fuel cell, combustion of hydrogen occurs to? ​

1. Produce high purity water.
2. Generate heat.
3. Remove adsorbed oxygen from electrode surface.
4. create potential difference between the two electrodes.

Q. Which of the following statements is correct regarding Galvanic cell ?

1. It converts electrical energy into chemical energy
2. It converts electrolyte into individual ions
3. It converts metal from its elemental state to the combined state
4. It converts chemical energy into electrical energy

Q. Electrode potential data of few cells is given below. Based on the data, arrange the ions in increasing order of their reducing power :- Fe3+(aq) + e– → Fe2+(aq); E° = +0.77 V Al3+(aq) + 3e– → Al(s); E° = –1.66 V Br2(aq) + 2e– → 2Br–(aq); E° = +1.09 V (1) Br– < Fe2+ < Al (2) Fe2+ < Al < Br– (3) Al < Br– < Fe2+ (4) Al < Fe2+ < Br–

Q. In a galvanic cell, anode is :

1. neutral
2. negatively charged
3. positively charged
4. both negatively and positively charged.

Q. Which of the following is a secondary cell?

1. Mercury cell
2. Dry cell
3. Lead storage cell
4. Leclanche cell

Q. Which of the following is a secondary cell?

1. Dry cell
2. Leclanche cell
3. Mercury cell
4. Lead storage cell

Q. Maxium potential difference between anode and cathode of electrochemical cell is observed when there is current in circuit.

1. maxium
2. minimum
3. no

Q. Maxium potential difference between anode and cathode of electrochemical cell is observed when there is current in circuit.

1. maxium
2. minimum
3. no

Q.

The standard electrode potentials are K⁺/K= -2.93V, Ag⁺/Ag = 0.80 V, so

1. Ag has a higher tendency to undergo reduction.

2. Ag⁺ has a higher tendency to undergo reduction.

3. K has a higher tendency to undergo reduction.

4. K⁺ has a higher tendency to undergo reduction.

Q. Which of the following is true about primary batteries?

1. Until the chemical components are active, primary batteries convert electrical energy into chemical energy.
2. It can be reused
3. It can be recharged
4. It cannot be reused.

Q.

Suppose that an alkaline dry cell was manufactured using cadmium metal rather than zinc. What happens to emf?

1. no change

2. the voltage would increase by 0.36V

3. the voltage would decrease by 0.36V

4. it would not work

Q. When an ammeter connected between the anode and cathode idicates a zero reading, then the emf of the cell is zero.

1. True
2. False

Q. Given below are the half - cell reactions
$M{n}^{2+}+2e^{-}\to Mn;E^{\circ }=-1.18eV$
$2(M{n}^{3+}+e^{-}\to M{n}^{2+});E^0=+1.51eV$
The $E^{\circ }$for $3M{n}^{2+}\to Mn+2M{n}^{3+}$ will be

1. -2.69 V; the reaction will not occur
2. -2.69 V; the reaction will occur
3. -0.33 V; the reaction will not occur
4. -0.33 V; the reaction will occur

Q. Consider the following half cells
$C{u}_{\left(s\right)}\to C{u}_{\left(aq\right)}^{2+}+2e^{-};E^o=-0.325V$
$C{u}_{\left(aq\right)}^{+}+e^{-}\to C{u}_{\left(s\right)};E^o=0.50V$
The $E^o$ for the reaction $2C{u}_{\left(aq\right)}^{+}\to C{u}_{\left(aq\right)}^{2+}+C{u}_{\left(s\right)}$ is

1. 0.175 V
2. 0.35 V
3. 0.675 V
4. 0.3375 V

Q.

Suppose that an alkaline dry cell was manufactured using cadmium metal rather than zinc. What happens to emf?

1. no change

2. the voltage would increase by 0.36V

3. the voltage would decrease by 0.36V

4. it would not work

Q. Given two reactions and their electrode potential values:
Reaction 1 :
$A(aq.)\rightleftharpoons A^{n+}(aq.)+n{e}^{-}$
$E^{\circ }=+2V$

Reaction 2:
$B(aq.)\rightleftharpoons B^{n+}(aq.)+n{e}^{-}$
$E^{\circ }=+4V$

Which of the following options is correct?

1. Tendency to gain electrons does not depend upon $E^{\circ }$
2. The reactant A has higher tendency to gain electrons than reactant B
3. None of the above
4. The reactant B has higher tendency to gain electrons than reactant A