A sample of (S)-enriched 2-butanol has ee = 40%. Pure (S)-2-butanol has [alpha] = +13.5 under the stated conditions. Select the correct statements.

The sample contains 70% (S) and 30% (R)

The specific rotation of the sample is +5.4

Mixing 40 g of this sample with 60 g of racemic 2-butanol gives a mixture of ee = 16%

The sample contains 70% (S) and 30% (R)

The sample contains 60% (S) and 40% (R)

The specific rotation of the sample is +5.4

Mixing 40 g of this sample with 60 g of racemic 2-butanol gives a mixture of ee = 16%

JEE Advanced levelOne or more correct optionsDifficulty 3 of 3st150

A sample of (S)-enriched 2-butanol has ee = 40%. Pure (S)-2-butanol has $[α] = + 13.5$ under the stated conditions. Select the correct statements.

AThe sample contains 70% (S) and 30% (R)
BThe sample contains 60% (S) and 40% (R)
CThe specific rotation of the sample is $+ 5.4$
DMixing 40 g of this sample with 60 g of racemic 2-butanol gives a mixture of ee = 16%

ee = 40% means %(S) = 50 + 20 = 70% and %(R) = 30%, so A is true and B is false.

[α] = 0.40 \times 13.5 = 5.4

, so C is true. The racemate carries no excess, so the 100 g mixture has excess (S) of 0.40 x 40 = 16 g and ee = 16%, so D is true.