1. Mass transfer coefficients can be of either local or overall type.

a. Explain carefully what the local and overall mass transfer coefficients represent.

b. How does the concentration gradient for the molar transfer rate differ when expressing the transfer in overall and local transfer coefficients respectively?

2. a. Explain the problems of flooding and channeling in packed tower

    b. Explain the construction and working of sieve tray, bubble cap tray and counterflow tray

3. Explain the differences between overall, Murphree and point tray efficiency.