Question

Magnitude of specific rotation of a compound is independent of:
A) Solvent
B) Concentration
C) Length of tube
D) Temperature

Answer 1

The term specific rotation is related to optical activity of compound. When a compound to be focused is put in an optical tube for finding its degree of rotation, then there are certain factors if they change the value of optical rotation also changes. We have solvent if it changes the value of optical rotation also changes, length of tube and temperature also have certain effects.

Complete step-by-step answer:
A compound is said to be optically active if it is rotating the plane polarizing light in some directions, left or right. The compound if rotates the ppl light in clockwise direction, then it is called as dextro rotatory and if it is rotating in anticlockwise direction, then it is called to be laevo rotatory.

This rotation is measured when a compound is taken in a polarimeter where you have to put it into a cell or we can call it a tube having some value of length. We measure its direction of rotation at a particular temperature, if temperature changes the value of specific rotation also changes.

The formula thus represented as –
$\left[ \alpha \right]_\lambda ^T\, = \,\dfrac{\alpha }{{l \times p}}$ Here, temperature and wavelength is specified thus if any of the value get changed you will get different value. Thus we can say specific rotation is dependent on solvent, length of tube and temperature. It doesn’t depend upon the concentration.

Hence the correct answer is option ‘B’.

Note: Solvent plays an important role because we are making a solution of a compound in that particular solvent so if we change the solvent the solution gets changed and gives a different value of specific rotation calculated in the polarimeter. Similarly, temperature also affects the value but concentration remains the same, that is specific rotation has the same value if we are changing its concentration.