278 Problems
equilibrium at 11000 revolutions per minute and at 25°C. The
following equilibrium concentrations were measured:Distance from axis
of rotation/cm 4.90 4.95 5.00 5.05 5.10 5.15
Concentration/'g dm~^3 1.30 1.46 1.64 1.84 2.06 2.3!The partial specific volume of the protein was 0.75 cm^3 g"^1 and the
density of the solution (assumed constant) was 1.00 g cm"^3. Calculate
the relative molecular mass of the protein.- The following osmotic pressures were measured for solutions
of a sample of polyisobutylene in benzene at 25°C:
Concentration/(g/m cm^3 ) 0.5 1.0 1.5 2.0
Osmotic pressure/'(cm solution) 1.03 2.10 3.22 4.39
(solution density = 0.88 g cm~^3 in each case)Calculate an average relative molecular mass.- A 0.01 mol dm~^3 aqueous solution of a colloidal electrolyte
(which can be represented as Na^X) is on one side of a dialysis
membrane, while on the other side of the membrane is an equal
volume of 0.05 mol dm"^3 aqueous sodium chloride. When Donnan
equilibrium is established, what net fraction of the NaCl will have
diffused into the compartment containing the colloidal electrolyte? - The following light-scattering data give values of the quantity
107 Kc/Re for solutions of cellulose nitrate dissolved in acetone:
Concentration/ Scattering angle
g dm~^3 (in relation to transmitted beam)
45° 32° 17° 30'
0.88 69.8 49.0 33.0
0.64 66.0 45.5 29.4
0.43 62.8 42.1 25.9Make appropriate extrapolations and calculate an average relative
molecular mass for the cellulose nitrate.