When 20 gm optically active compound is placed in a 10 dm tube, in a 200 ml solution rotates the PPL (plane polarized light) by 30° :
(a) What is the angle of rotation if above solution is diluted to 1 litre?
(b) What is the specific angle of rotation if above solution is diluted to 1 litre?
Write answer of part (a) and (b) in the same order and present the four digit number as answer in OMR sheet.
For example : If answer of (a) is 9 and (b) is 99 then fill 0999 in OMR sheet.

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answer is 630.

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Detailed Solution

Mass =20 gm
Volume = 200 ml
$c = \frac{m a s s}{v o l u m e} = \frac{20}{200} = 0.1 \frac{g m}{m l}$
Length of tube (l)= 10 dm
Optical rotation $θ = 30^{0}$
$α = \frac{θ}{C X l}$
$α = \frac{30}{0.1 X 10} = 30$
(A) If solution is diluted to one litre then new volume
V= 1000ml
$θ = ?$
$α = \frac{θ}{C X l}$ ; $30 = \frac{θ}{\frac{20}{1000} X 10}; θ = 6 °$
(B) Specific rotation does not change with change in conc. Or volume or length etc. Therefore it is 30⁰.