Answer the following: The molar conductivity at infinite dilution for and for respectively…
Answer the following:
(a)[1.0]
The molar conductivity at infinite dilution for $\lambda^\circ_{\text{H}^+} = 348\cdot65\text{ S cm}^2\text{mol}^{-1}$ and for $\lambda^\circ_{\text{CH}_3\text{COO}^-} = 41\cdot4\text{ S cm}^2\text{mol}^{-1}$ respectively.
Calculate the degree of dissociation ($\alpha$) of acetic acid if its molar conductivity ($\Lambda_m$) is $40\cdot65\text{ S cm}^2\text{mol}^{-1}$.
(b)[1.0]
Compounds [A] and [B] are two electrolytes. Upon dilution, the molar conductivity of compound [A] increases 3 times while that of [B] increases 30 times. Which one of the two is a weak electrolyte? Why?
(c)[1.0]
Can copper sulphate solution be stored in a zinc pot? Give a reason for your answer by referring to the values given below:
$E^\circ_{\text{Zn}^{2+}/\text{Zn}} = -0\cdot76\text{ V}, E^\circ_{\text{Cu}^{2+}/\text{Cu}} = +0\cdot34\text{ V}$
Answer
Answer (a)
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Formula:
$\Lambda^\circ_m(\text{CH}_3\text{COOH}) = \lambda^\circ_{\text{H}^+} + \lambda^\circ_{\text{CH}_3\text{COO}^-}$
$\alpha = \frac{\Lambda_m}{\Lambda^\circ_m}$
Substitution:
$\Lambda^\circ_m = 348\cdot65 + 41\cdot4 = 390\cdot05\text{ S cm}^2\text{mol}^{-1}$
$\alpha = \frac{40\cdot65\text{ S cm}^2\text{mol}^{-1}}{390\cdot05\text{ S cm}^2\text{mol}^{-1}} = 0\cdot1042\text{ (or } 10\cdot42\%\text{)}$
Final answer: 0.1042
Final answer: 0.1042
Answer (b)
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Compound [B] is the weak electrolyte.
Reason:
A weak electrolyte is only partially dissociated at normal concentrations. Upon dilution, its degree of dissociation ($\alpha$) increases significantly according to Ostwald's dilution law, leading to a large increase in the number of conducting ions and hence a steep increase in molar conductivity (30 times). In contrast, a strong electrolyte is already completely dissociated, and dilution causes only a modest increase in molar conductivity (3 times) due to reduced interionic attractions.
Answer (c)
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No, copper sulphate solution cannot be stored in a zinc pot.
Reason:
$E^\circ_{\text{Zn}^{2+}/\text{Zn}} = -0\cdot76\text{ V}$ is more negative than $E^\circ_{\text{Cu}^{2+}/\text{Cu}} = +0\cdot34\text{ V}$, meaning zinc is more reactive and a stronger reducing agent than copper. Zinc spontaneously displaces copper from $\text{CuSO}_4$:
$\text{Zn(s)} + \text{Cu}^{2+}\text{(aq)} \longrightarrow \text{Zn}^{2+}\text{(aq)} + \text{Cu(s)}$
Since $E^\circ_{\text{cell}} = +0\cdot34 - (-0\cdot76) = +1\cdot10\text{ V} > 0$, the reaction is thermodynamically spontaneous, and the zinc pot will dissolve.
From ISC 2026 Chemistry Paper 1, question 17(i).