Surface Chemistry - Result Question 22
23. Among the following, the surfactant that will form micelles in aqueous solution at the lowest molar concentration at ambient conditions, is
$(2008,3 M)$
(a) $\mathrm{CH}_3\left(\mathrm{CH}2\right){15} \mathrm{~N}^{+}\left(\mathrm{CH}_3\right)_3 \mathrm{Br}^{-}$
(b) $\mathrm{CH}_3\left(\mathrm{CH}2\right){11} \mathrm{OSO}_3^{-} \mathrm{Na}^{+}$
(c) $\mathrm{CH}_3\left(\mathrm{CH}_2\right)_6 \mathrm{COO}^{-} \mathrm{Na}^{+}$
(d) $\mathrm{CH}_3\left(\mathrm{CH}2\right){11} \mathrm{~N}^{+}\left(\mathrm{CH}_3\right)_3 \mathrm{Br}^{-}$
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Answer:
Correct Answer: 23. (a)
Solution:
Larger the hydrophobic fragment of surfactant, easier will be the micellisation, smaller the crticial micelle concentration. Therefore, $\mathrm{CH}_3\left(\mathrm{CH}2\right){15} \mathrm{~N}^{+}\left(\mathrm{CH}_3\right)_3 \mathrm{Br}^{-}$will have the lowest crticial micelle concentration.
BETA
