Chemical Reaction Engineering Questions and Answers – Mole Balances

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This set of Chemical Reaction Engineering Multiple Choice Questions & Answers (MCQs) focuses 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
View Answer

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.
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2. Chemical reaction rate is ___________
a) an extensive property
b) an intensive property
c) a chemical property
d) a physical property
View Answer

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
View Answer

Answer: b
Explanation: rA indicates the rate of formation of A whereas –rA indicates the rate of disappearance of A.
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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
View Answer

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
View Answer

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 = \(\frac{1}{V} \frac{dNi}{dt}. \)
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6. In ________ there are no spatial variations in concentration and temperature.
a) PFR
b) Tubular reactor
c) CSTR
d) Packed bed reactor
View Answer

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
View Answer

Answer: c
Explanation: Rate law is experimentally determined. It is a product of rate constant and algebra function of concentration.
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8. In a PFR, the extent of reaction achieved does not depend on the shape of the reactor.
a) True
b) False
View Answer

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
View Answer

Answer: c
Explanation: The reaction rate is defined in terms of reaction volume for homogeneous reactions.
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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
View Answer

Answer: d
Explanation: The reaction rate of gaseous phase reaction is dependent on all of them.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter