Question

Specific rotation of sugar solution is O.5 deg kg. 200 kgm-3 of impure sugar solution is taken in a sample polarimeter tube of length 20 cm and optical rotation is found to be 19?. The percentage of purity of sugar is

• A. 20%
• B. 80%
• C. 95%
• D. 89%

Answer 1

Answer: (C)

The strength of solution is given by x $c=\frac{\theta }{l\times s}$ . where the symbols have their usual meanings. Here, $\theta =19{}^{\circ },l=20cm=0.20m,$ $s=0.5\mathrm{deg}{m}^2/kg.$ $\therefore$ $c=\frac{19}{0.20\times 0.5}=190kg-m^{-3}$ The sugar sample dissolved in a $m^3$ of water is 200 kg in which 190 kg is pure sugar. Therefore, purity is $=\frac{190}{200}\times 100$ $=95$