Chemical Reaction Engineering Multiple Choice Questions & Answers on “Mole Balances”.
1. The unit for rate of reaction for a fluid-solid catalytic reaction is _______
A. mol/m3.s
B. mol/s. g catalyst
C. mol/s. mmHg
D. mol/dm3.s
Answer: B
Explanation: Rate of reaction for a fluid-solid catalytic reaction is defined as the number of moles of A reacted per unit time per unit mass of catalyst.
2. Chemical reaction rate is ___________
A. an extensive property
B. an intensive property
C. a chemical property
D. a physical property
Answer: B
Explanation: Chemical reaction rate depends on temperature and concentration. Hence, it is an intensive property.
3. –rA is a universal notation for reaction rate. What does the negative sign indicate?
A. Rate of formation of A
B. Rate of disappearance of A
C. Rate of dissociation of A
D. Rate of association of A
Answer: B
Explanation: rA indicates the rate of formation of A whereas –rA indicates the rate of disappearance of A.
4. General mole balance equation of species ‘i’ at any instant is as follows: ________
A. Rate of moles of ‘i’ in = Rate of moles of ‘i’ out
B. Rate of moles of ‘i’ in + Rate of moles of ‘i’ out = Rate of moles of ‘i’ accumulated
C. Rate of moles of ‘i’ in + Rate of moles of ‘i’ accumulated = Rate of moles ‘i’ out
D. Rate of moles of ‘i’ in – Rate of moles of ‘i’ consumed by reaction – Rate of moles of ‘i’ out = Rate of moles of ‘i’ accumulated
Answer: D
Explanation: Governed by principles of conservation of mass and energy the following equation is the basic equation in Chemical engineering for design of all process units.
IN – OUT + Generation – Consumption = Accumulation.
5. 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
Answer: B
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}. )
6. In ________ there are no spatial variations in concentration and temperature.
A. PFR
B. Tubular reactor
C. CSTR
D. Packed bed reactor
Answer: C
Explanation: CSTR is operated in such a way that the reaction mixture is perfectly mixed. Hence, there are no spatial variations.
7. The kinetic rate law is ______
A. a differential eqn
B. a linear eqn
C. an algebraic eqn
D. a quadratic eqn
Answer: C
Explanation: Rate law is experimentally determined. It is a product of rate constant and algebra function of concentration.
8. In a PFR, the extent of reaction achieved does not depend on the shape of the reactor.
A. True
B. False
Answer: A
Explanation: From design eqn (frac{dFi}{dV}) = ri. The reaction rate doesn’t depend on shape of the reactor.
9. The unit for rate of reaction for a homogeneous reaction is __________
A. mol/s. g catalyst
B. mol/s. mmHg
C. mol/s. m3
D. mol/s. m2
Answer: C
Explanation: The reaction rate is defined in terms of reaction volume for homogeneous reactions.
10. Rate of gaseous phase reaction depends on __________
A. Temperature of reactants only
B. Pressure of reactants only
C. Concentration of reactants only
D. Temperature, Pressure and Concentration of reactants
Answer: D
Explanation: The reaction rate of gaseous phase reaction is dependent on all of them.