Question

Mole balance equation for a perfectly mixed batch reactor is _______

(a) \(\frac{dNi}{dt}\) = 0

(b) \(\frac{dNi}{dt}\) = ri V

(c) \(\frac{dNi}{dt} = \int_0^V\)ri dV

(d) \(\frac{dNi}{dt}\) = ri

This question was addressed to me at a job interview.

The query is from Mole Balances topic in portion Basic Concepts of Chemical Reaction Engineering

Answer 1

Right answer is (b) \(\frac{dNi}{dt}\) = ri V

Best explanation: General mole balance for batch reactor is \(\frac{dNi}{dt} = \int_0^V\)ri dV. For perfectly mixed batch reactors there are no spatial variations and above equation can be modified as

ri = \(\frac{1}{V} \frac{dNi}{dt}. \)