Electrochemistry Test

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Electrochemistry Test - 18

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Weekly Quiz Competition

Question 1
1 / -0

The cell potential $$(E)$$ and the free energy change $$(\triangle G)$$ accompanying an electrochemical reaction are related by:

A
$$\triangle G = nF\ \log E$$

B
$$\triangle G = nFE$$

C
$$\triangle G = -nFE$$

D
$$-\triangle G = nF\ \log E$$

Solution

For an electrochemical reaction, the free energy change is given as
$$\Delta G = - nF E$$
Question 2
1 / -0

Which one of the following conditions will increase the voltage of the cell represented by the equation?
$$Cu(s) + 2Ag^{+}(aq.) \rightleftharpoons Cu^{2+}(aq.) + 2Ag(s)$$.

A
Increase in the dimension of $$Cu$$ electrode

B
Increase in the dimension of $$Ag$$ electrode

C
Increase in the concentration of $$Cu^{2+}$$ ion

D
Increase in the concentration of $$Ag^{+}$$ ion

Solution

Cell voltage will increase, either by increasing the concentration of $$Cu^{2+}$$ ion or by decreasing the concentration of $$Ag^{+}$$.
$$Q = \dfrac {[Cu^{2+}]}{[Ag^{+}]}$$
Lesser is the value of $$Q$$, greater is the cell voltage.
Question 3
1 / -0

One faraday of electricity will liberate one gram mole of the metal from the solution of:

A
$$BaCl_{2}$$

B
$$CuSO_{4}$$

C
$$AlCl_{3}$$

D
$$NaCl$$

Solution

Answer is option (D) $$NaCl$$
As only in $$NaCl$$ $$1e^-$$ is involved.
Question 4
1 / -0

Among $$Na, Hg, S, Pt$$ and graphite, which can be used as electrodes in electrolytic cells having aqueous solutions?

A
$$Hg$$ and $$Pt$$

B
$$Hg, Pt$$ and graphite

C
$$Na$$ and $$S$$

D
$$Na, Hg$$ and $$S$$

Solution

sodium and sulphur reacts with water whereas $$Hg,Pt$$ and graphite donot,hence can be used as electodes.
Question 5
1 / -0

On heating, sodium and sulphur can be melted. Molten sodium and molten sulphur are used ?

A
For refining lead

B
As a medium for extracting metals

C
As catalysts

D
As electrodes in a modern kind of battery

Solution

Molten sodium and molten sulphur are used as electrodes in modern kind of battery because of high capacity and stable cyclic performance and stability.]
They have highly active molten electrode.
Cathode typically made of molten sulphur and anode is sodium.
Question 6
1 / -0

Selenium has the unusual property of being a good conductor in light but a poor conductor in the dark. It was, therefore, used in making.

A
Shaded glass

B
Photo-electric cells

C
Photo chemical celles

D
Chromatic lenses

Solution

Since, selenium is a good conductor of electricity in light, but poor conductor in dark.
$$\therefore$$ It is used in photo- electric cells.
Since, photocell is an electronic device which works on the principle of photo electric effect and convert light energy into electrical energy.
Question 7
1 / -0

Kunal took few iron turnings and mixed them well with Sulphur powder. He could separate the iron turnings with the help of a magnet. He heated the mixture for some time and tried to separate the iron turnings with the magnet but he could not. Why?

A
On heating, a chemical change takes place and a new compound is formed.

B
On heating, iron becomes non-magnetic hence, it is not attracted by magnet.

C
On heating, a physical change takes place hence iron and Sulphur gets mixed up.

D
On heating, iron evaporates and only sulphur is left behind

Solution

$$ Fe + S \overset{Heat}{\rightarrow} FeS$$
Iron Iron Sulphide

On heating iron and Sulphur, a new substance, iron sulphide is formed, so it is a chemical change.

Hence the correct option is A.
Question 8
1 / -0

Is the reaction, $$2Al + 3Fe^{2+}\rightleftharpoons 2Al^{3+} + 2Fe$$ possible?

A
No, because standard oxidation potential of $$Al < Fe$$

B
Yes, because standard oxidation potential of $$Al > Fe$$

C
Cannot be predicted

D
Yes, because aluminium is a strong oxidising agent

Solution

Yes, the reaction is possible because the reduction potential of Al is more ( - 1.66 V) than that of Fe (-0.41 V),
so, oxidation of Al and reduction of Fe will takes place.
Question 9
1 / -0

Which molecule electrolysis temperature is maximum?

A
$$As{H}_{3}$$

B
$${NH}_{3}$$

C
$${PH}_{3}$$

D
$$Sb{H}_{3}$$

Solution

depend on size of element so sb is bigger size then other and D is currect option
Question 10
1 / -0

The charge which is not possible, is:

A
$$-1.6\times 10^{-19}C$$

B
$$-3.2\times 10^{-20}C$$

C
$$-4.8\times 10^{-19}C$$

D
$$-3.2\times 10^{-18}C$$

Solution

The least possible value of a charge is the charge present on an electron which is $$1.6\times{10}^{-19}$$ Coulomb as according to the quantization law .Charge on a body has to be an integral multiple of the charge of an electron.

So Option B is incorrect

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Electrochemistry Test - 18

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Electrochemistry Test - 18

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Question 1

$$\triangle G = nF\ \log E$$

$$\triangle G = nFE$$

$$\triangle G = -nFE$$

$$-\triangle G = nF\ \log E$$

Solution

Question 2

Increase in the dimension of $$Cu$$ electrode

Increase in the dimension of $$Ag$$ electrode

Increase in the concentration of $$Cu^{2+}$$ ion

Increase in the concentration of $$Ag^{+}$$ ion

Solution

Question 3

$$BaCl_{2}$$

$$CuSO_{4}$$

$$AlCl_{3}$$

$$NaCl$$

Solution

Question 4

$$Hg$$ and $$Pt$$

$$Hg, Pt$$ and graphite

$$Na$$ and $$S$$

$$Na, Hg$$ and $$S$$

Solution

Question 5

For refining lead

As a medium for extracting metals

As catalysts

As electrodes in a modern kind of battery

Solution

Question 6

Shaded glass

Photo-electric cells

Photo chemical celles

Chromatic lenses

Solution

Question 7

On heating, a chemical change takes place and a new compound is formed.

On heating, iron becomes non-magnetic hence, it is not attracted by magnet.

On heating, a physical change takes place hence iron and Sulphur gets mixed up.

On heating, iron evaporates and only sulphur is left behind

Solution

Question 8

No, because standard oxidation potential of $$Al < Fe$$

Yes, because standard oxidation potential of $$Al > Fe$$

Cannot be predicted

Yes, because aluminium is a strong oxidising agent

Solution

Question 9

$$As{H}_{3}$$

$${NH}_{3}$$

$${PH}_{3}$$

$$Sb{H}_{3}$$

Solution

Question 10

$$-1.6\times 10^{-19}C$$

$$-3.2\times 10^{-20}C$$

$$-4.8\times 10^{-19}C$$

$$-3.2\times 10^{-18}C$$

Solution

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