mass transfer :

A 0.021 m thick slab made of 3.8% gelatin in water is saturated with methanol at 5 C. Initially, the concentration of methanol in the slab was 0.412 kg mol/m. The slab was suddenly immersed in a tank that contains water with methanol concentration of 0.012 kg mol/m. After 160 hours of exposure, the methanol concentration at the midpoint of the slab was 44% of the original concentration.

a) Calculate the methanol mass transfer coefficient (k.) in (m/s) at the mid-point of the

slab.

b) What would be the concentration at the mid-point of the slab if the slab thickness was increased by 21%?