Alanine has pK_a1 = 2.34 and pK_a2 = 9.69. At pH 7.0 the ratio [anion]/[cation] (i.e. H2N-CH(CH3)-COO- to H3N+-CH(CH3)-COOH) is closest to

JEE Advanced levelSingle correct optionDifficulty 3 of 3bm201

Alanine has $p K_{a 1} = 2.34$ and $p K_{a 2} = 9.69$ . At pH 7.0 the ratio [anion]/[cation] (i.e. $H X_{2} N - CH (CH X_{3}) - COO X^{-}$ to $H X_{3} N X^{+} - CH (CH X_{3}) - COOH$ ) is closest to

\frac{[ zwitterion ]}{[ cation ]} = 1 0^{p H - p K_{a 1}} = 1 0^{4.66}

;

\frac{[ anion ]}{[ zwitterion ]} = 1 0^{p H - p K_{a 2}} = 1 0^{- 2.69}

. Product

= 1 0^{2 \times 7 - 12.03} = 1 0^{1.97} = 93.3