Question

1-The boiling point of dimethyl sulfoxide at 1 atm is 190 oC. Use the boiling point nomograph to determine the boiling point of dimethyl sulfoxide at 1.0 mmHg.

2-The refractive index of an unknown liquid was measured during a hot summer day and was found to be 1.5016 at 30 oC. Calculate the corrected refractive index for this unknown compound.

Answer 1

1. In boiling point nomograph, there are three lines, one on the exteme left is the vertical line indicates observed boiling point, middle one is the verticla line indicates bolinig point corrected to 760 mm Hg, extreme right is the slightly curved line indicating pressure in mm Hg. To determine the boi.ing point of dimethyl sulfoxide at 1.0 mmHg. we need the boiling point of dimethyl sulfoxide at 1 atm i.e. given 190 deg C. now we mark a line from 20 mm Hg to 190 deg C on the middle line and extent it to that of the extreme left line, the intecsecting point indicates the bolinig point of dimethyl sulfoxide at 1.0 mmHg. On extending the above line we get the boiling point around 50-55 deg. C. We can obtained the best point on drawing a line on monograph.

2. since the measured value of refractive indexmust be corrected to 20 deg C, so ,corrected reftactive index is shown using formula below,

N²⁰_D =1.5016-t (0.00045)

where, t=measure temperature i.e. 30 deg C -20 deg C

so, N²⁰_D =1.5016- 10(0.00045)

=1.5016-0.0045

=1.4971