Specific rotation of sugar solution is `0.01 SI` units. `200 kg-m^(-3)` of impure sugar solution is taken in a polarimeter tube of length `0.25m` and an optical rotation of `0.4` rad is observed. The percentage of purity of sugar in the sample is

Options

A. `11%`
B. `20%`
C. `80%`
D. `89%`

Answer

C

Explanation

Specific rotation of sugar solution is
`alpha = ("angle of rotation")/("length of tube" xx "concentration")`
`= (theta)/(l xx C)`
`:. C = (theta)/(l alpha)`
`= (0.4)/(0.25 xx 0.01) = 160 kg//m^(3)`
Thus, purity of sugar solution
`= (160)/(200) xx 100 = 80%`