Question

The specific rotation of (S)-2-butanol is +13.5. If 0.119 g of its enantiomer is dissolved in 10.0 mL of ethanol and

Answer 1

Answer:

+15.8°

Explanation:

The formula for the observed rotation (α) of an optically active sample is

α = [α]lc

where

l = the cell path length in decimetres

c = the concentration in units of g/100 mL

[α] = the specific rotation in degrees  

1. Convert the concentration to units of g/100 mL

$c = \frac{\text{0.119 g}}{\text{10.0 mL}} \times \frac{10 }{10 } =\frac{\text{1.19 g}}{\text{100 mL}}$

2. Calculate the observed rotation

$\alpha = (+13.3 ^{\circ}) \times 1.19 \times 1 = +15.8^{\circ}$