Question

Temperature dependence of viscosity of water is given by the following equation: ln (viscosity) = - 11.0318 + 1057.51 / (temperature + 214.624) where temperature is in OF and viscosity is in Ibm / (ft. s). (a) Consider a dilute aqueous solution of acetic acid in water. Apply EXCEL software to calculate and plot the diffusion coefficient of acetic acid in water as a function of temperature at the temperature range between 35 to 200 OF. (You need to select a constant temperature interval of 5 OF). (b) Re-solve part (a), but replace acetic acid with methanol. (c) Re-solve part (a), but replace acetic acid with acetone.

Answer 1

For this question to find the diffusion coefficient or diffusivity, we use the relation,

where D_T1 and D_T2 are diffusivities at T1 and T2 and and   are viscosities of water at T1 and T2.

We find the values of D_T1 and at a reference temperature of 25^oC or 77^oF.

For acetone- water mixure, D_T1 = 1.16*10^-5 cm² /s and = 1.864*10^-5 lbm/ft.s

The following is a screenshot of the excel page

Similarly we can find for the other two components using initial value of diffusivity at 77OF