Sodium stearate $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{16} \mathrm{COO}^{-} \mathrm{Na}^{+}$is an anionic surfactant which forms micelles in oil. Choose the correct statement for it from the following:

(C) It forms spherical miclelles with $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{16}-$ group pointing towards the centre of sphere.

(A) It forms spherical micelles with $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{16}$-group pointing outwards on the surface of sphere.

(B) It forms non-spherical micelles with $-\mathrm{COO}^{\ominus}$ group pointing outwards on the surface

(D) It forms non- spherical micelles with $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{16}$ - group pointing towards the centre.

JEE Main · 2021 · 25 Jul 2021 · Shift 1 · Surface Chemistry

Sodium stearate

CH_{3} (CH_{2})_{16} COO^{-} Na^{+}

is an anionic surfactant which forms micelles in oil. Choose the correct statement for it from the following:

(A)It forms spherical micelles with $CH_{3} (CH_{2})_{16}$ -group pointing outwards on the surface of sphere.
(B)It forms non-spherical micelles with $- COO^{⊖}$ group pointing outwards on the surface
(C)It forms spherical miclelles with $CH_{3} (CH_{2})_{16} -$ group pointing towards the centre of sphere.✓ Correct
(D)It forms non- spherical micelles with $CH_{3} (CH_{2})_{16}$ - group pointing towards the centre.

Answer: (C)

In a non-polar medium (oil), anionic surfactants like sodium stearate form reverse micelles. The hydrophobic hydrocarbon tails (

CH_{3} (CH_{2})_{16} -

) point towards the center (the oil phase), while the polar carboxylate heads (

- COO^{-}

) orient outward. These micelles are typically spherical. The correct answer is (C).

JEE Main · 2021 · 25 Jul 2021 · Shift 1 · Single correct option