# Chemical Reaction Engineering Questions and Answers – Fluid-Fluid Reactions – Absorption Systems with Chemical Reaction

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This set of Chemical Reaction Engineering Problems focuses on “Fluid-Fluid Reactions – Absorption Systems with Chemical Reaction”.

1. A microfluid is the one in which ____
a) Fluid motion is restricted
b) Fluid molecules are free to move
c) Molecules do not take part in reaction
d) Fluid is compressed in due course of reaction

Explanation: A microfluid is characterized by free movement of fluid molecules. Molecules collide and intermix.

2. For early mixing, which of the following reactors/ combination of reactors is used?
a) CSTR followed by PFR
b) PFR
c) Two CSTRs in series
d) Two CSTRs in parallel

Explanation: CSTR is followed by a PFR for early mixing. This combination favours reactions of negative order.

3. For a macrofluid, the average concentration of reactant in the exit stream is _______
a) $$\frac{\overline{C_A}}{C_{A0}}$$ = $$\int_0^∞ \frac{C_A}{C_{A0}}$$dt
b) $$\frac{\overline{C_A}}{C_{A0}}$$ = E.dt
c) $$\frac{\overline{C_A}}{C_{A0}}$$ = $$\int_0^∞$$E.dt
d) $$\frac{\overline{C_A}}{C_{A0}}$$ = $$\int_0^∞ \frac{C_A}{C_{A0}}$$E.dt

Explanation: The average concentration of reactant in the exit stream is the summation of the products of reactant concentration remaining between t and t+dt and the fraction that exits between t and t+dt. The fraction exiting between t and t+dt is given as Edt.

4. State true or false.
Late mixing is favoured for reactions with positive order.
a) True
b) False

Explanation: The reactant is at high concentration and reacts rapidly as n > 1. Hence, PFR is followed by CSTR for late mixing.

5. State true or false.
Macrofluids form large aggregates.
a) True
b) False

Explanation: Macrofluid exhibits segregation. Globules, each consisting of a large number of molecules do not mix well with the other globules.