The pH and conductance of a weak acid (HX) was found to be 5 and 4 10⁻⁵ ~S , respectively. The conductance was measured under standard condition using a cell where the electrode plates having a surface area of 1 ~cm ² were at a distance of

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The pH and conductance of a weak acid (HX) was found to be 5 and 4 10⁻⁵ ~S , respectively. The conductance was measured under standard condition using a cell where the electrode plates having a surface area of 1 ~cm ² were at a distance of 15 cm apart. The value of the limiting molar conductivity is _ _ _ _ S m ² ~mol ⁻¹ . (nearest integer) (Given : degree of dissociation of the weak acid ( ) 1 )

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Given: pH = 5, so [H^+] = 10⁻⁵ M; G = 4 10⁻⁵ S; A = 1 cm²; l = 15 cm Cell constant = l/A = 15 cm⁻¹ Specific conductivity: = G (l/A) = 4 10⁻⁵ 15 = 6 10⁻⁴ S/cm For weak acid HX: [H^+] = C = 10⁻⁵ M Using = C °_m 1000 °_m = 1000 C = 1000 6 10⁻⁴ 10⁻⁵ = 6 10^4 S cm² mol⁻¹ Converting: °_m = 6 10^4 10⁻⁴ = 6 S m² mol⁻¹

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