Electrochemistry Test

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Electrochemistry Test - 26

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following statements is incorrect?

A
Tarnishing of silver is due to the formation of $$Ag_2S$$ and $$Ag_2O$$

B
Green deposit on Cu terminal of battery are due to the formation of $$CuCO_3$$

C
Brown deposits on Fe is due to formation of rust

D
White deposits on Al pan is due to the formation of $$Al_2O_3$$

Solution

Explanation:
1). The composition of the tarnish layers on silver in air : It is often found to consist mainly of the sulphide $$Ag_2S$$ with some chloride $$AgCl$$ and oxide $$Ag_2O$$
$$Ag+air(O_2+H_2S)\rightarrow Ag_2O+Ag_2S$$
Hence option A is correct.

2). Green deposit on Cu terminal of the battery is due to the formation of :
$$Cu+H_2O+CO_2+O_2\rightarrow CuCO_3+Cu(OH)_2$$
Hence option B is correct.

3). Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the presence of water or air moisture.
Hence option C is correct.

4). The pesky white mineral deposit usually forms on the surface of your pans after boiling hard water. The white spots appear as a result of calcium and salt deposits.
Hence option D is wrong

Option D is the correct answer which is incorrect among all.
Question 2
1 / -0

The standard reduction potentials of $$Cu^{2+}/ Cu$$ and $$Cu^{2+}/ Cu^{+}$$ are $$ 0.337 V $$and $$0.153 V$$ respectively.

The standard electrode potential of $$Cu^{+}/Cu$$ half cell is:

A
$$0.184 V$$

B
$$0.827 V$$

C
$$0.521 V$$

D
$$0.490 V$$

Solution

$$Cu^{2+} + 2e \rightarrow Cu; E^o = 0.337 V \therefore - \Delta G^o = -2 \times 0.337 \times F$$

$$Cu+ \rightarrow Cu^{2+} +e^-; E^o = 0.153 V \therefore - \Delta G^o = 0.153 \times 1 \times F$$
$$- - -$$ (by substracting)
----------------------------------------------------------------------------------------------------
$$Cu^+ + e \rightarrow Cu , -\Delta G^o =- 0.521 F$$

$$\because - \Delta G^o = -nFE$$

$$\therefore -0.521 F = -F E^o$$

$$\therefore E^o = 0.521 V$$

Hence,option C is correct.
Question 3
1 / -0

An apparatus used for the measurement of the quantity of electricity passed is known as a:

A
calorimeter

B
cathetometer

C
coulometer

D
colorimeter

Solution

Coulometry is the technique that determines the amount of matter transformed during an electrolysis reaction, by measuring the amount of electricity (in coulombs) consumed or produced.
Question 4
1 / -0

The tarnishing of silver ornaments in the atmosphere is due to the formation of:

A
$$Ag_2O, Ag_2S$$

B
$$AgNO_3, Ag_2S$$

C
$$AgOH, Ag_2CO_3$$

D
$$Ag$$

Solution

In the air, a silver object tarnishes owing to the reaction of silver with hydrogen sulfide and oxygen.

Reaction:
$$Ag+ air (O_2 + H_2S) \rightarrow Ag_2O + Ag_2S$$
Question 5
1 / -0

The passage of electricity in the Daniell cell when $$Zn$$ and $$Cu$$ electrodes are connected:

A
from $$Cu$$ to $$Zn$$ inside the cell

B
from $$Cu$$ to $$Zn$$ outside the cell

C
from $$Zn$$ to $$Cu$$ outside the cell

D
none of the above
Question 6
1 / -0

In moist air, iron is oxidized to give:

A
iron$$[II]$$ oxide

B
iron$$[III]$$ oxide

C
iron$$[II]$$ hydroxide

D
iron$$[II]$$ sulphide

Solution

When iron is subjected to moist air it is oxidised as per the following reactions:

$$ Fe \rightarrow Fe^{2+} + 2e^-;$$ Oxidation takes place

In the presence of moisture the following reaction takes place:

$$ 2Fe^{2+} + 2H_2O + \dfrac{1}{2}O_2 \rightarrow Fe_2O_3 +4H^+$$

In $$ Fe_2O_3 $$ iron is in $$ +3$$ oxidation state.

Hence option B is correct.
Question 7
1 / -0

Assertion: Cations migrate at cathode during electrolysis.
Reason: Reduction always occurs at cathode.

A
Both Assertion and Reason are true and Reason is the correct explanation of Assertion

B
Both Assertion and Reason are true but Reason is not the correct explanation of Assertion

C
Assertion is true but Reason is false

D
Assertion is false but Reason is true

E
Both Assertion and Reason are false

Solution

During electrolysis,
at anode:
$$Y^- \rightarrow Y + e^-$$
at cathode:
$$X^+ + e^- \rightarrow X$$
Question 8
1 / -0

Which of the following statements is incorrect?

A
Conductance of an electrolytic solution increases with dilution.

B
Conductance of an electrolytic solution decreases with dilution.

C
Conductivity of an electrolytic solution decreases with dilution.

D
Equivalent conductivity of an electrolytic solution increases with dilution.

Solution

On dilution, ionic mobility increases but the number of ions present in 1 mL decreases. Thus, only conductivity decreases and rest all increase.

Thus, options A, C, and D are correct and option B is incorrect.
Question 9
1 / -0

Which metals does not corrode easily?

A
Gold

B
Iron

C
Aluminium

D
Zinc

Solution

In the activity series, metals are on the top of the series react and corrode easily as these metals are highly reactive like iron corrodes easily in the presence of water and air forming its oxide layer while metals present at the bottom are least reactive and do not corrode easily like gold, silver and platinum are some of them.

Option $$(A)$$ is correct.
Question 10
1 / -0

Which of these metals do not corrode?

A
Lead

B
Copper

C
Platinum

D
Silver

Solution

Corrosion is a process through which metals in manufactured states return to their natural oxidation states. This process is a reduction-oxidation reaction in which the metal is being oxidized by its surroundings, often the oxygen in air. As platinum is least reactive so it will not corrode.

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Re-Attempt Weekly Quiz Competition

Electrochemistry Test - 26

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Electrochemistry Test - 26

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Question 1

Tarnishing of silver is due to the formation of $$Ag_2S$$ and $$Ag_2O$$

Green deposit on Cu terminal of battery are due to the formation of $$CuCO_3$$

Brown deposits on Fe is due to formation of rust

White deposits on Al pan is due to the formation of $$Al_2O_3$$

Solution

Question 2

$$0.184 V$$

$$0.827 V$$

$$0.521 V$$

$$0.490 V$$

Solution

Question 3

calorimeter

cathetometer

coulometer

colorimeter

Solution

Question 4

$$Ag_2O, Ag_2S$$

$$AgNO_3, Ag_2S$$

$$AgOH, Ag_2CO_3$$

$$Ag$$

Solution

Question 5

from $$Cu$$ to $$Zn$$ inside the cell

from $$Cu$$ to $$Zn$$ outside the cell

from $$Zn$$ to $$Cu$$ outside the cell

none of the above

Question 6

iron$$[II]$$ oxide

iron$$[III]$$ oxide

iron$$[II]$$ hydroxide

iron$$[II]$$ sulphide

Solution

Question 7

Both Assertion and Reason are true and Reason is the correct explanation of Assertion

Both Assertion and Reason are true but Reason is not the correct explanation of Assertion

Assertion is true but Reason is false

Assertion is false but Reason is true

Both Assertion and Reason are false

Solution

Question 8

Conductance of an electrolytic solution increases with dilution.

Conductance of an electrolytic solution decreases with dilution.

Conductivity of an electrolytic solution decreases with dilution.

Equivalent conductivity of an electrolytic solution increases with dilution.

Solution

Question 9

Gold

Iron

Aluminium

Zinc

Solution

Question 10

Lead

Copper

Platinum

Silver

Solution

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