Electrochemistry Test

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Electrochemistry Test - 71

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Weekly Quiz Competition

Question 1
1 / -0

Standard electrode potential data are useful for understanding the suitability of an oxidant in a redox titration. Some half-cell reactions and their standard potentials are given below:

$$MnO_{4}^{-}(aq)+8H^{+}(aq)+5e^{-}\rightarrow Mn^{2+}(aq)+4H_{2}O(l);$$ $$E^{\circ}= 1.51V$$
$$Cr_{2}O_{7}^{2-}(aq)+14H^{+}(aq)+6e^{-}\rightarrow 2Cr^{3+}(aq)+7H_{2}O(l);$$ $$E^{\circ}= 1.38V$$
$$Fe^{3+}(aq)+e^{-}\rightarrow Fe^{2+}(aq);$$ $$E^{\circ}= 0.77V$$
$$Cl_{2}(g)+2e^{-}\rightarrow 2Cl^{-}(aq);$$ $$E^{\circ}= 1.40V$$

Identify the only incorrect statement regarding the quantitative estimation of aqueous $$Fe(NO_{3})_{2}$$

A
$$MnO_{4}^{-}$$ can be used in aqueous $$HCl$$

B
$$Cr_{2}O_{7}^{2-}$$ can be used in aqueous $$HCl$$

C
$$MnO_{4}^{-}$$ can be used in aqueous $$H_{2}SO_{4}$$

D
$$Cr_{2}O_{7}^{2-}$$ can be used in aqueous $$H_{2}SO_{4}$$

Solution
Question 2
1 / -0

The decreasing order of standard electrode potential of $$Mg, K, Ba$$ and $$Ca$$ is

A
$$K,Ca,Ba,Mg$$

B
$$Ba, Ca, K, Mg$$

C
$$Ca, Mg, K, Ba$$

D
$$Mg, Ca, Ba, K$$

Solution

To find electrode potential, electrochemical series is used.
The alkaline earth metals are weaker reducing agents than alkali metals. And like alkali metals, the reducing character of the alkaline earth metals increases down the group.

So, the decreasing order of standard electrode potential will be :

Mg > Ca > Ba > K

Thus, option D is correct.
Question 3
1 / -0

Two electrochemical cells are assembled in which the following reactions occur:

$$ V^{2+}+VO^{2+}+2H^{+} \rightarrow 2V^{3+}+H_{2}O\ ;\ E_{cell}^{\circ} = 0.616\ V$$

$$ V^{3+}+Ag^{+}+H_{2}O \rightarrow VO^{2+}+Ag(s)+2H^{+}\ ;\ E_{cell}^{\circ} = 0.439\ V$$

If $$ E_{Ag^{+}|Ag}^{\circ} = 0.799\ V,$$ what is $$ E_{V^{3+}|V^{2+}}^{\circ}?$$

A
$$-0.256\ V$$

B
$$+0.256\ V$$

C
$$+1.854\ V$$

D
$$-1.854\ V$$

Solution
Question 4
1 / -0

From the following $$E^{\circ}$$ values for the half-cells:

$$(i)\ D\rightarrow D^{2+}+2e^{-};E^{\circ}=-1.5V$$

$$(ii)\ B^{+}+e^{-}\rightarrow B;E^{\circ}=-0.5V$$

$$(iii)\ A^{3-}\rightarrow A^{2-}+e^{-};E^{\circ}=1.5V$$

$$(iv)\ C^{2+}+e^{-}\rightarrow C^{+};E^{\circ}= +0.5V$$

Which combination of two half-cells would result in a cell with the largest potential?

A
$$(i)$$ and $$(iii)$$

B
$$(i)$$ and $$(iv)$$

C
$$(iii)$$ and $$(iv)$$

D
$$(ii)$$ and $$(iv)$$

Solution
Question 5
1 / -0

Statement $$I$$: Electrolysis of $$ CuCl_{2}(aq)$$ gives 1 mole of Cu and 1 mole of $$ Cl_{2}$$ by the passage of suitable charge.
Statement $$II$$: Equal equivalents of Cu and $$ Cl_{2}$$ are formed during the passage of same charge.

A
If both statements are CORRECT, and Statement $$II$$ is the CORRECT explanation of Statement $$I$$.

B
If both statements are CORRECT, and Statement $$II$$ is NOT the CORRECT explanation of Statement $$I$$.

C
If Statement $$I$$ is CORRECT, but Statement $$II$$ is INCORRECT.

D
If Statement $$I$$ is INCORRECT,but Statement $$II$$ is CORRECT.
Question 6
1 / -0

Statement $$I$$: An electrochemical cell can be set up only when the redox reaction is spontaneous.
Statement $$II$$: A reaction is spontaneous if free energy change at constant temperature and pressure is negative.

A
If both statements are Correct, and Statement $$II$$ is the Correct explanation of Statement $$I$$.

B
If both statements are Correct, and Statement $$II$$ is NOT the Correct explanation of Statement $$I$$.

C
If Statement $$I$$ is Correct, but Statement $$II$$ is Incorrect.

D
If Statement $$I$$ is Incorrect, but Statement $$II$$ is Correct.

Solution
Question 7
1 / -0

The graph represent a current-voltage behaviour of water. Choose the correct option:

A
Ohm's law is obeyed

B
Electrolysis in general do not obey ohm's law

C
Dissociation takes place at E, and it obeys Ohm's law thereafter

D
Ohm's law is not valid for low voltage

Solution
Question 8
1 / -0

Which of the following solutions have highest resistance?

A
1N - NaCl

B
0.05 N - NaCl

C
2N - NaCl

D
0.1 N - NaCl

Solution
Question 9
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Which of the following statements does not differentiate between electrochemical cell and electrolytic cell?

A
Spontaneous or non-spontaneous nature of the chemical process.

B
Chemical reactions occurring at the electrodes

C
Positive and negative nature of anode.

D
EMF measurement.

Solution
Question 10
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Statement $$II$$: In an electrochemical cell, anode and cathode are, respectively, negative and positive electrode.
Statement $$II$$: At anode, oxidation takes place and at cathode reduction takes place.

A
If both statements are CORRECT, and Statement $$II$$ is the CORRECT explanation of Statement $$I$$.

B
If both statements are CORRECT, and Statement $$II$$ is NOT the CORRECT explanation of Statement $$I$$.

C
If Statement $$I$$ is CORRECT, but Statement $$II$$ is INCORRECT.

D
If Statement $$I$$ is INCORRECT, but Statement $$II$$ is CORRECT.

Solution