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Read the passage and answer the questions.
‘Freidrich Wilhelm Georg Kohlrausch was a German physicist who studied the electrical conductivity…
‘Freidrich Wilhelm Georg Kohlrausch was a German physicist who studied the electrical conductivity of electrolytic solutions. From 1875-1879 he performed numerous experiments with aqueous solutions of different salts, acids and other electrolytes. He concluded that each type of migrating ion has a specific conductivity, and it does not depend on the origin of the ion. In a simple way, his conclusions were applicable to strong electrolytes as well as more complex behaviour was observed for weak electrolytes.’
Source: https://doi.org/10.1002/elsa.202160008
(a)[1.0]
What did Kohlrausch mean when he said that each ion has specific conductivity which is independent of origin of ions?
(b)[2.0]
Explain the law proposed by Kohlrausch with example.
(c)[2.0]
How do you propose to calculate the molar conductivity of a weak electrolyte (acetic acid) by using his law?
Answer
Answer (a)
Official answer key$\mathrm{Na^+}$ ions have the same value of specific conductivity irrespective of their source being sodium sulphate or sodium nitrate.
Answer (b)
Official answer keyCorrect explanation of the law with example.
$\mathrm{CH_3COONa + HCl \rightarrow CH_3COOH + NaCl}$
Answer (c)
Official answer keyIf molar conductivity at infinite dilution of HCl, NaCl and sodium acetate is known then molar conductivity of acetic acid at infinite dilution can be calculated using this law.
From ISC 2025 Practice Chemistry, question 97.
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