Electrochemistry Test

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Electrochemistry Test - 59

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Weekly Quiz Competition

Question 1
1 / -0

Assertion : A voltaic cell spontaneously converts chemical energy into electrical energy.

Reason : A voltaic cell needs an externally applied current to work.

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

Statement I is correct whereas statement II is false.

Voltaic Cells :

An electrochemical cell which causes external electric current flow can be created using any two different metals since metals differ in their tendency to lose electrons.

Zinc more readily loses electrons than copper, so placing zinc and copper metal in solutions of their salts can cause electrons to flow through an external wire which leads from the zinc to the copper.

Hence the correct option is C.
Question 2
1 / -0

The below reaction is the gold-plating process reaction.
$${ Au }^{ 3+ }\left( aq \right) +3{ e }^{ - }\rightarrow Au\left( s \right) $$
If $$0.600 g$$ of $$Au$$ is plated onto a metal, how many coulombs are used?

A
$$299 C$$

B
$$868 C$$

C
$$2,990 C$$

D
$$8,680 C$$

Solution

$$Au^{3+} + 3e^- \rightarrow Au(s)$$
1 mole of $$Au^{3+}$$ requires 3 mol of electrons for reduction to $$Au(s)$$.
Moles of $$Au$$ in 0.600 g = $$\dfrac {0.600}{197}= 0.003$$
1 mol of $$Au^{3+}$$ requires 3 mol , so 0.003 mol of $$Au^{3+} $$ requires$$ = 3 \times 0.003 = 0.009$$ moles of electrons.
1 mol of electron has = 96500 C charge
0.009 moles of electrons has = $$96500 \times 0.009 = 868 C$$
Question 3
1 / -0

In an electrochemical cell, reduction takes place at anode BECAUSE oxidation always takes place at the cathode.

A
F, F

B
F,T

C
T,T

D
T,F

Solution

The electrode at which oxidation takes place in a electrochemical cell is called the anode. The electrode at which reduction occurs is called the cathode. The identity of the cathode and anode can be remembered by recognizing that positive ions, or cations, flow toward the cathode, while negative ions, or anions, flow toward the anode.
Question 4
1 / -0

Which of these processes could be associated with the following reaction.
$$\displaystyle 2{ H }_{ 2 }O\rightarrow 2{ H }_{ 2 }+{ O }_{ 2 }$$.
i. Electrolysis
ii. Neutralization
iii. Decomposition

A
i only

B
iii only

C
i and iii only

D
i and ii only

E
ii and iii only

Solution

Electrolysis of water is its decomposition to give hydrogen and oxygen gases due to the passage of an electric current.

$$ 2H_2O + energy \rightarrow O_2 + 2H_2$$
Question 5
1 / -0

A salt bridge :

A
is not used in a galvanic cell

B
completes the circuit

C
increases the rate of reaction

D
provides an easy handle to carry the cell

E
None of these

Solution

A salt bridge completes the circuit.

A salt bridge connects two half cells. It helps in flow of ions between two half cells. Thus, a salt bridge maintains electrical neutrality.

Hence, the correct option is B.
Question 6
1 / -0

A positive cell potential tells you ________.

A
the reaction is not spontaneous

B
the reaction is spontaneous

C
the reaction will not occur without intervention

D
$$\Delta G$$ is negative

E
both the reaction is spontaneous and $$\Delta G$$ is negative

Solution

$$\Delta G=- nFE_{cell}^o$$
A positive cell potential tells you that both the reaction is spontaneous and $$\Delta G$$ is negative.

Question 7

1 / -0

Consider the table of standard reduction potentials shown below.

Half-reaction	$$E^{\circ}$$
$$Cl_{2} + 2e^{-}\rightarrow 2Cl^{-}$$	$$1.36\ V$$
$$O_{2} + 4H^{+} + 4e^{-} \rightarrow 2H_{2}O$$	$$1.23\ V$$
$$2H_{2}O + 2e^{-} \rightarrow H_{2} + 2OH^{-}$$	$$-0.83\ V$$
$$Rb^{+} + e^{-} \rightarrow Rb$$	$$-2.93\ V$$

Use the information from the table and your knowledge of electrochemistry to predict the CORRECT net ionic equation for the reaction that will occur when an aqueous solution of rubidium chloride undergoes electrolysis.

$$2Rb^{+} + 2Cl^{-} \rightarrow 2Rb + Cl_{2}$$

$$2H_{2}O \rightarrow 2H_{2} + O_{2}$$

$$H_{2} + 2OH^{-} + 2Rb^{+} \rightarrow 2Rb + 2H_{2}O$$

$$4Cl^{-} + O_{2} + 4H^{+} \rightarrow 2H_{2}O + 2Cl_{2}$$

Solution

From the given table, we have;

Rb as the lowest reduction potential therefore it undergo oxidation

and $$Cl_2$$ have the highest oxidation potential therefore it undergo reduction.

so, the net reaction becomes

$$2Rb^+ + 2Cl^- \rightarrow 2Rb + Cl_2$$

Question 8
1 / -0

A steady current of $$10.0$$ Amps is passed through a nickel production cell of $$15$$ minutes.
Which of the following is the correct expression for calculating the number of grams of nickel produced?
Note:
$$\bullet 1\ faraday = 96,500\ Coulombs$$
$$\bullet$$ The electroytic cell involves the following half-reaction:
$$Ni_{(aq)}^{2+} + 2e^{-} \rightarrow Ni_{(s)}$$

A
$$\dfrac {(10.0)(15)(96,500)}{(59)(60)} g$$

B
$$\dfrac {(10.0)(15)(59)}{(60)(96,500)} g$$

C
$$\dfrac {(10.0)(15)(60)(59)}{(96,500)(2)} g$$

D
$$\dfrac {(96,500)(59)}{(10)(15)(60)(2)} g$$

Solution

According to Faraday's Law
$$W= \cfrac {Z \times I \times t}{F}$$
$$W$$= mass of compound
$$Z$$= Equivalent mass $$F$$= 96500
$$I$$= Current in Ampere
$$t$$= time in seconds
$$\Rightarrow W= \left(\cfrac {59}{2}\right)\cfrac {\times 15\times 60 sec\times 10A}{96500}$$
$$\Rightarrow W= \cfrac {(10.0)(15)(60)(59)}{(96500)(2)}g$$
Question 9
1 / -0

Two half-cells have potentials $$-0.44$$ and $$0.799$$ volt respectively. These two are coupled to make a galvanic cell. Which of the following will be true?

A
Electrode of half-cell potential $$-0.44\ V$$ will act as anode

B
Electrode of half-cell potential $$-0.44\ V$$ will act as cathode

C
Electrode of half-cell potential $$0.799\ V$$ will act as anode

D
Electrode of half-cell potential $$-0.44\ V$$ will act as a positive terminal

Solution

Galvanic Cell:-
$$\rightarrow$$ In Galvanic cell,left hand side (anode), oxidation occurs. At right hand side electrode(cathode) , reduction occurs.
$$\rightarrow$$ The sum of the oxidation half reaction at anode and reduction half reaction at cathode is the overall cell reaction.
$$\rightarrow$$ Electrode with positive value of electrode potential suggest forward reaction i.e. reduction at cathode. So, electrode with 0.799 volt will act as cathode.
$$\rightarrow$$Electrode with negative value of electrode potential suggest reverse reaction i.e. oxidation at anode. Hence, electrode with -0.44 volt will act as anode.
Question 10
1 / -0

(A) 1 faraday = 96,500 coulomb.
It is a charge of 1 mole electrons.
(R) 1 faraday charge liberates one gram equivalent of substance at an electrode.

A
Both (R) and (A) are true and reason is the. correct explanation of assertion

B
Both (R) and (A) are true but reason is not correct explanation of assertion

C
Assertion (A) is true but reason (R) is false

D
Assertion (A) and reason (R) both are false

E
Assertion (A) is false but reason (R) is true

Solution

1 faraday charge liberates one gram equivalent of substance at an electrode.
1 faraday is the charge equals to 96500 coulombs.
Both (R) and (A) are true and reason is the. correct explanation of assertionHence option A is correct.

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Electrochemistry Test - 59

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Electrochemistry Test - 59

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Question 1

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 2

$$299 C$$

$$868 C$$

$$2,990 C$$

$$8,680 C$$

Solution

Question 3

F, F

F,T

T,T

T,F

Solution

Question 4

i only

iii only

i and iii only

i and ii only

ii and iii only

Solution

Question 5

is not used in a galvanic cell

completes the circuit

increases the rate of reaction

provides an easy handle to carry the cell

None of these

Solution

Question 6

the reaction is not spontaneous

the reaction is spontaneous

the reaction will not occur without intervention

$$\Delta G$$ is negative

both the reaction is spontaneous and $$\Delta G$$ is negative

Solution

Question 7

$$2Rb^{+} + 2Cl^{-} \rightarrow 2Rb + Cl_{2}$$

$$2H_{2}O \rightarrow 2H_{2} + O_{2}$$

$$H_{2} + 2OH^{-} + 2Rb^{+} \rightarrow 2Rb + 2H_{2}O$$

$$4Cl^{-} + O_{2} + 4H^{+} \rightarrow 2H_{2}O + 2Cl_{2}$$

Solution

Question 8

$$\dfrac {(10.0)(15)(96,500)}{(59)(60)} g$$

$$\dfrac {(10.0)(15)(59)}{(60)(96,500)} g$$

$$\dfrac {(10.0)(15)(60)(59)}{(96,500)(2)} g$$

$$\dfrac {(96,500)(59)}{(10)(15)(60)(2)} g$$

Solution

Question 9

Electrode of half-cell potential $$-0.44\ V$$ will act as anode

Electrode of half-cell potential $$-0.44\ V$$ will act as cathode

Electrode of half-cell potential $$0.799\ V$$ will act as anode

Electrode of half-cell potential $$-0.44\ V$$ will act as a positive terminal

Solution

Question 10

Both (R) and (A) are true and reason is the. correct explanation of assertion

Both (R) and (A) are true but reason is not correct explanation of assertion

Assertion (A) is true but reason (R) is false

Assertion (A) and reason (R) both are false

Assertion (A) is false but reason (R) is true

Solution

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