19sp rotation = (100 * observed angle of rotation) / (length in dm * gm of solute in 100 cc of soln)
from here,we express obs angle of rotation in terms of sp. rotation....then calculate concentration due to the two species !
.....you get the answer !( remember express concentration in terms of g/cc i.e. g/ml)
here, concentration = 0.1 g/cc
thus, obs rotation = (4.44 * 0.1 * 13.5 )/100 =0.06
(hopefully, no calculation errors) ! [68]
