Chemistry - GOC Question with Solution | TestHub

A compound dissolves in aqueous $\mathrm{NaOH}$ when it is acidic enough to form a water-soluble sodium salt ($\mathrm{p}{K}_{\mathrm{a}}$ well below that of water, 15.7).

(i) 4-methylphenol ($\mathrm{p}{K}_{\mathrm{a}}$ 10.2): soluble. (ii) cyclohexanol (about 17): not. (iii) 4-chlorobenzoic acid: soluble. (iv) benzyl alcohol (15.4): not. (v) 2,4-dinitrophenol: soluble. (vi) but-2-yne has no acidic hydrogen: not. (vii) benzenesulphonic acid: soluble. (viii) acetophenone (α-H, $\mathrm{p}{K}_{\mathrm{a}}$ about 24): not. (ix) 4-nitrobenzyl alcohol is still an alcohol: not. (x) 3-nitrophenol (8.4): soluble. (xi) 2-naphthol (9.5): soluble.

Soluble: (i), (iii), (v), (vii), (x), (xi) = 6.

Answer: 6.