CBSE Class 12 Chemistry 2024: question 17

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Step-by-step solution

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1. (a) Kohlrausch's law: The limiting molar conductivity of an electrolyte equals the sum of the individual contributions of its cation and anion: ${\Lambda }_m^{\circ }={\nu }_{+}{\lambda }_{+}^{\circ }+{\nu }_{-}{\lambda }_{-}^{\circ }$. Here ${\lambda }_{+}^{\circ }$ and ${\lambda }_{-}^{\circ }$ are the limiting molar conductivities of the cation and anion, and ${\nu }_{+}$, ${\nu }_{-}$ are the numbers of each ion per formula unit.

   1 mark

2. (b) Faraday's first law: The mass of substance deposited or liberated at an electrode during electrolysis is directly proportional to the quantity of electricity passed: $m=ZIt$. Here $m$ is the mass deposited, $Z$ the electrochemical equivalent, $I$ the current and $t$ the time.

   1 mark

Answer: (a) ${\Lambda }_m^{\circ }={\nu }_{+}{\lambda }_{+}^{\circ }+{\nu }_{-}{\lambda }_{-}^{\circ }$; (b) $m=ZIt$ (mass deposited ∝ charge passed)

Revise the chapter

• Chapter: Electrochemistry (notes, formulas, where marks are lost and every past question)
• Topic: Conductivity, Molar Conductivity and Kohlrausch's Law