Electrochemistry 2 Question 1
1. The decreasing order of electrical conductivity of the following aqueous solution is
$0.1 \mathrm{M}$ formic acid $(A)$,
$0.1 \mathrm{M}$ acetic acid $(B)$,
$0.1 \mathrm{M}$ benzoic acid $(C)$.
(2019 Main, 12 April II)
(a) $A>C>B$
(b) $C>B>A$
(c) $A>B>C$
(d) $C>A>B$
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Solution:
- Electrical conductivity of the given aqueous solutions depends on the degree of ionisation. Degree of ionisation is directly proportional to the acidic strength. Electron withdrawing groups (EWGs) increases the stability of the carboxylate ion by dispersing the negative charge through resonance effect on the conjugate while electron donating groups (EDGs) decreases the stability of the carboxylate ion by intensifying the negative charge.
Acidity of carboxylic acids increases due to the presence of electron withdrawing groups (EWGs)
Acidity of carboxylic acids decreases due to the presence of electron donating groups
The correct order of acidic strength and electrical conductivity is as follows:
$$ \underset{A}{\mathrm{HCOOH}}>\underset{C}{\mathrm{PhCOOH}}>\underset{B}{\mathrm{CH}_{3} \mathrm{COOH}} $$
