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Q. No.A standard aqueous solution of a weak acid HX has a pH of 5 and shows a conductance of 4×10–5 S when placed in a conductivity cell with electrode separation of 15 cm and cross-sectional area of 1 cm².
Assuming that the degree of dissociation of HX is very small, calculate the limiting molar conductivity of the solution (in Sm2mol-1).
1. Three (3)2. Five (5)
3. Six (6)
4. Seven (7)
Subtopic: Conductance & Conductivity |
Level 4: Below 35%
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Subtopic: Nernst Equation |
Level 4: Below 35%
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Hints
Calculate \(\mathrm{E}_{\mathrm{Cl}^{-} / \mathrm{AgCl} / \mathrm{Ag}}^0 \text { (in millivolts) }\)
\(\begin{aligned} & \text { Given : }\left(E_{\mathrm{Ag}^{+} / \mathrm{Ag}}^{\circ}=0.79 \mathrm{~V}\right), \quad\left(K_{\mathrm{sp}}(\mathrm{AgCl})=10^{-10}\right) \\ & \frac{2.303 \mathrm{RT}}{\mathrm{~F}}=0.059 . \end{aligned}\)
1. 100
2. 300
3. 300
4. 400
\(\begin{aligned} & \text { Given : }\left(E_{\mathrm{Ag}^{+} / \mathrm{Ag}}^{\circ}=0.79 \mathrm{~V}\right), \quad\left(K_{\mathrm{sp}}(\mathrm{AgCl})=10^{-10}\right) \\ & \frac{2.303 \mathrm{RT}}{\mathrm{~F}}=0.059 . \end{aligned}\)
1. 100
2. 300
3. 300
4. 400
Subtopic: Relation between Emf, G, Kc & pH |
Level 4: Below 35%
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Hints
0.18 M HQ solution has molar conductivity \(\frac { 1 } {30}\) times the molar conductivity of 0.02 M HZ solution. Find the value of \(pK_a (HQ)-pK_a(HZ)\), given that \(\alpha\) is very less than 1.
Assume that \(\lambda_{\mathrm{m}}^{\infty}\left(\mathrm{Q}^{-}\right)=\lambda_{\mathrm{m}}^{\infty}\left(\mathrm{Z}^{-}\right) \):
1. 2
2. 0
3. 4
4. 8
Assume that \(\lambda_{\mathrm{m}}^{\infty}\left(\mathrm{Q}^{-}\right)=\lambda_{\mathrm{m}}^{\infty}\left(\mathrm{Z}^{-}\right) \):
1. 2
2. 0
3. 4
4. 8
Subtopic: Conductance & Conductivity |
Level 4: Below 35%
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Hints
Electrolysis of aqueous solution of \(CuSO_4\) is carried out, where 300 mg of copper is deposited (atomic mass of Cu = 63.54). After this 600 milli amp. current is further passed for 28 minutes. Calculate total volume of \(O_2\) released (in ml), given that 1 mole of a gas occupy 22.4 litres.
Given half reactions:
\(\mathrm{Cu}^{+2}(\mathrm{aq})+2 \mathrm{e}^{-} \longrightarrow \mathrm{Cu}(\mathrm{~s})\)
\(2 \mathrm{H}_2\mathrm{O}(l) \longrightarrow \mathrm{O}_2(\mathrm{~g})+4 \mathrm{H}^{+}(\mathrm{aq})+4 \mathrm{e}^{-}\)
1. 110
2. 111.15
3. 101.5
4. 80.5
Given half reactions:
\(\mathrm{Cu}^{+2}(\mathrm{aq})+2 \mathrm{e}^{-} \longrightarrow \mathrm{Cu}(\mathrm{~s})\)
\(2 \mathrm{H}_2\mathrm{O}(l) \longrightarrow \mathrm{O}_2(\mathrm{~g})+4 \mathrm{H}^{+}(\mathrm{aq})+4 \mathrm{e}^{-}\)
1. 110
2. 111.15
3. 101.5
4. 80.5
Subtopic: Electrode & Electrode Potential | Faraday’s Law of Electrolysis |
70%
Level 2: 60%+
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Hints
Find the pH, above which \(O_2\) will be evolved at anode:
\(\begin{aligned} & \mathrm{E}_{\mathrm{M}^{+2}(\mathrm{aq}) / \mathrm{M}(\mathrm{~s})}^{\circ}=0.997 \mathrm{~V}, \mathrm{E}_{\mathrm{O}_2(\mathrm{~g}) / \mathrm{H}_2 \mathrm{O}(\ell)}^{\circ}=+1.23 \mathrm{~V} \\ & \operatorname{Pt}(\mathrm{~s})\left|\mathrm{O}_2(\mathrm{~g})\right| \mathrm{H}^{+}(\mathrm{aq}) \| \mathrm{M}^{+2} \mid \mathrm{M} \end{aligned}\)
(Given that \(\left.2.303 \frac{\mathrm{RT}}{\mathrm{~F}}=0.059\right)\)
1. 4
2. 6
3. 10
4. 12
\(\begin{aligned} & \mathrm{E}_{\mathrm{M}^{+2}(\mathrm{aq}) / \mathrm{M}(\mathrm{~s})}^{\circ}=0.997 \mathrm{~V}, \mathrm{E}_{\mathrm{O}_2(\mathrm{~g}) / \mathrm{H}_2 \mathrm{O}(\ell)}^{\circ}=+1.23 \mathrm{~V} \\ & \operatorname{Pt}(\mathrm{~s})\left|\mathrm{O}_2(\mathrm{~g})\right| \mathrm{H}^{+}(\mathrm{aq}) \| \mathrm{M}^{+2} \mid \mathrm{M} \end{aligned}\)
(Given that \(\left.2.303 \frac{\mathrm{RT}}{\mathrm{~F}}=0.059\right)\)
1. 4
2. 6
3. 10
4. 12
Subtopic: Electrode & Electrode Potential | Nernst Equation | Relation between Emf, G, Kc & pH |
Level 3: 35%-60%
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Hints
For the electrochemical cell:
Pt | HSnO₂⁻, Sn(OH)₆²⁻, OH⁻ || Bi₂O₃, Bi | Pt
The reaction quotient (Q) is 10⁶.
Given:
E°(Sn(OH)₆²⁻ / HSnO₂⁻) = −0.90 V
E°(Bi₂O₃ / Bi) = −0.44 V
If the cell potential Ecell is expressed as x × 10⁻¹ V, find the value of x:
1. 22. 4
3. 6
4. 8
Subtopic: Nernst Equation |
73%
Level 2: 60%+
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Hints
A cell is given as
\(\mathrm{M}(\mathrm{~s})\left|\mathrm{M}^{\mathrm{n}+}(\mathrm{aq}) \| \mathrm{M}^{+\mathrm{n}}(\mathrm{aq})\right| \mathrm{M}(\mathrm{~s})\)
For which of the following condition, \(E_{cell}\) is positive:
1. \(C_1 < C_2\) (If \(C_1\) is concentration at cathode)
2. \(C_2 < C_1\) (If \(C_1\) is concentration at anode)
3. \(C_1 < C_2\) (If \(C_2 \) is concentration at anode)
4. \(C_1 > C_2\) (If \(C_1\) is concentration at cathode)
\(\mathrm{M}(\mathrm{~s})\left|\mathrm{M}^{\mathrm{n}+}(\mathrm{aq}) \| \mathrm{M}^{+\mathrm{n}}(\mathrm{aq})\right| \mathrm{M}(\mathrm{~s})\)
For which of the following condition, \(E_{cell}\) is positive:
1. \(C_1 < C_2\) (If \(C_1\) is concentration at cathode)
2. \(C_2 < C_1\) (If \(C_1\) is concentration at anode)
3. \(C_1 < C_2\) (If \(C_2 \) is concentration at anode)
4. \(C_1 > C_2\) (If \(C_1\) is concentration at cathode)
Subtopic: Electrolytic & Electrochemical Cell |
60%
Level 2: 60%+
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Hints
A cell representation is given below:
\(Ag/ AgCl || FeCl_2 , FeCl_3 / Pt\)
Which of the following can increase the EMF of cell ?
(i) By increasing concentration of \(Fe^{2+}\)
(ii) By increasing concentration of \(Fe^{3+}\)
(iii) By decreasing concentration of \(Fe^{2+}\)
(iv) By decreasing concentration of \(Fe^{3+}\)
(v) By increasing concentration of \(Cl^-\)
1. i, iv, v
2. ii, iii, v
3. iii, iv, v
4. i, iii, v
\(Ag/ AgCl || FeCl_2 , FeCl_3 / Pt\)
Which of the following can increase the EMF of cell ?
(i) By increasing concentration of \(Fe^{2+}\)
(ii) By increasing concentration of \(Fe^{3+}\)
(iii) By decreasing concentration of \(Fe^{2+}\)
(iv) By decreasing concentration of \(Fe^{3+}\)
(v) By increasing concentration of \(Cl^-\)
1. i, iv, v
2. ii, iii, v
3. iii, iv, v
4. i, iii, v
Subtopic: Nernst Equation |
58%
Level 3: 35%-60%
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Hints
Calculate the standard cell potential for the given reaction:
\(\mathrm{Fe}^{2+}(\mathrm{aq})+\mathrm{Ag}^{+}(\mathrm{aq}) \rightarrow \mathrm{Fe}^{3+}(\mathrm{aq})+\mathrm{Ag}(\mathrm{~s})\)
Given :
\(\begin{array}{ll} \mathrm{Ag}^{+}+\mathrm{e}^{-} \rightarrow \mathrm{Ag} & \mathrm{E}^0=\mathrm{xV} \\ \mathrm{Fe}^{2+}+2 \mathrm{e}^{-} \rightarrow \mathrm{Fe} & \mathrm{E}^0=\mathrm{yV} \\ \mathrm{Fe}^{3+}+3 \mathrm{e}^{-} \rightarrow \mathrm{Fe} & \mathrm{E}^0=\mathrm{zV} \end{array}\)
1. x + y – z
2. x + 2y – 3z
3. y – 2x
4. x + 2y
\(\mathrm{Fe}^{2+}(\mathrm{aq})+\mathrm{Ag}^{+}(\mathrm{aq}) \rightarrow \mathrm{Fe}^{3+}(\mathrm{aq})+\mathrm{Ag}(\mathrm{~s})\)
Given :
\(\begin{array}{ll} \mathrm{Ag}^{+}+\mathrm{e}^{-} \rightarrow \mathrm{Ag} & \mathrm{E}^0=\mathrm{xV} \\ \mathrm{Fe}^{2+}+2 \mathrm{e}^{-} \rightarrow \mathrm{Fe} & \mathrm{E}^0=\mathrm{yV} \\ \mathrm{Fe}^{3+}+3 \mathrm{e}^{-} \rightarrow \mathrm{Fe} & \mathrm{E}^0=\mathrm{zV} \end{array}\)
1. x + y – z
2. x + 2y – 3z
3. y – 2x
4. x + 2y
Subtopic: Relation between Emf, G, Kc & pH |
60%
Level 2: 60%+
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Hints
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