Fall 2014CEE 2502

Physical Chemical Principles of Environmental Engineering

Homework No. 2Properties of Suspension

1. Compute the diffusivity of a sphere with a diameter of 1.6×10-6 cm and a density of 1.05 g/cm3 in air at 5 oC and normal atmospheric pressure.

2. Measurement of the diffusion coefficient for enzyme urease in water at 20 oC yielded a value of 3.4×10-7 cm2/sec. If the density of urease is 1.37 g/cm3, calculate the molecular weight of enzyme urease. Compare the obtained result with actual molecular weight of urease of 490 kg/mol and provide explanation for possible differences.

3. Suppose you make Kool-Aid in a container that is about 30 cm tall. It is a cylindrical pitcher with a radius of 5 cm. First you put the cup (1 cup = 236.6 cm3) of sugar (assume that pure glucose with molecular weight of 180 g/mol is used) and Kool-Aid mix in the bottom of the container (assume that Kool-Aid and sugar have identical properties). Then you pour 8 cups of water into the container. Without stirring, how long will it take for the sugar to be evenly distributed throughout the water? The density of sugar is 1.5620 g/cm3. The diffusion coefficient for sugar in water is 0.52 x 10-5 cm2/s and solubility of glucose (saturated water solution) is 5.6 x 10-3 mol/cm3.