Question

A tube of sugar solution 20 cm long is placed between crossed nicols and illuminated with light of wavelength 6×10⁻⁵ cm If the optical rotation produced is 13∘ and the specific rotation is 65∘ determine the strength of the solution

A. 0.1g/
B. 0.2g/
C. 0.9g/
D. 1.0g/

Answer 1

The strength of the solution is determined as 0.1 g/cc. (Option A).

How to calculate the strength of the solution?

The strength of the solution is calculated by applying the following method as shown below.

The angle of rotation is directly proportional to the concentration of a solution.

α = (θ) / ( L × c )

Where;

• α is specific rotation
• θ is optical rotation
• L is length of the tube (decimeter)
• c is concentration of the solution

The given parameters include;

length of the tube, L = 20 cm = 2 dm

optical rotation, θ = 13 ⁰C

specific rotation α = 65 ⁰C

The strength of the solution is calculated as;

c = (θ) / (L × α)

c = (13 ) / ( 2 x 65)

c = 0.1 g/cc

13 = 65 × 20 × c