MHT CET · Chemistry · Electrochemistry

The molar conductivities at infinite dilution for sodium acetate, HCI and NaCI are 91 S $c m^{2}$ $m o l^{- 1}, 425.9 S c m^{2} m o l^{- 1}$ and $126.4 S c m^{2} m o l^{- 1}$ respectively. The molar conductivity of acetic acid at infinite dilution is

A $39.05 S c m^{2} m o l^{- 1}$
B $530.9 S c m^{2} m o l^{- 1}$
C $300.5 S c m^{2} m o l^{- 1}$
D $930.5 S c m^{2} m o l^{- 1}$

Verified Solution

Answer & Solution

Correct Answer

(A) $39.05 S c m^{2} m o l^{- 1}$

Step-by-step Solution

Detailed explanation

Key Idea kohlrausch law of independent migration of ions can be used to calculate

Δ_{m}^{o}

for weak electrolyte such as acetic acid.
Given,

Δ_{m (N a A C)}^{o} = 91 S c m^{2} m o l^{- 1}

Δ_{m (H C I)}^{o} = 425.9 S c m^{2} m o l^{- 1}

Δ_{m (N a C l)}^{o} = 126.4 S c m^{2} m o l^{- 1}

Using Kohlrausch law, to find the molar conductivity of acetic acid.

Δ_{m (H A C)}^{o} = λ_{H^{+}}^{o} + λ_{A C^{-}}^{o}

= λ_{H^{+}}^{o} + λ_{C l^{-}}^{o} + λ_{A C^{-}}^{o} + λ_{N a^{+}}^{o} - λ_{C l^{-}}^{o} - λ_{N a^{+}}^{o}

= Δ_{m (H C I)}^{o} + Δ_{m (N a A C)}^{o} - Δ_{m (N a C l)}^{o}

= (425.9 + 91.0 - 126.4) S c m^{2} m o l^{- 1}

= 390.5 S c m^{2} m o l^{- 1}

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

Explore more questions on app

From MHT CET

Explore more questions on app

The molar conductivities at infinite dilution for sodium acetate, HCI and NaCI are 91 S cm2 mol-1,425.9 S cm2mol-1 and 126.4 S cm2mol-1 respectively. The molar conductivity of acetic acid at infinite dilution is

Step-by-step Solution

The molar conductivities at infinite dilution for sodium acetate, HCI and NaCI are 91 S $c m^{2}$ $m o l^{- 1}, 425.9 S c m^{2} m o l^{- 1}$ and $126.4 S c m^{2} m o l^{- 1}$ respectively. The molar conductivity of acetic acid at infinite dilution is