Chemical Reaction Engineering Questions and Answers – Reaction Order and Elementary Rate Law


This set of Chemical Reaction Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Reaction Order and Elementary Rate Law”.

1. Molecularity refers to an elementary reaction.
a) True
b) False
View Answer

Answer: a
Explanation: Elementary reaction occurs in single reaction step with no intermediates and molecularity is the number of particles involved in the reaction.

2. Molecularity is ___________ value and order is ___________ value.
a) an integer, a fractional
b) a fractional, an integer
c) both fractional
d) both integers
View Answer

Answer: a
Explanation: Order is empirical, hence can be a fractional value but molecularity refers to the mechanism and is applicable only for elementary reactions.

3. The overall order of reaction for –rA = kCA0.7CB1.3 is _______
a) 0
b) 1
c) 2
d) 3
View Answer

Answer: c
Explanation: Order w.r.t A is 0.7 and B is 1.3.Hence, Overall order is 2.

4. What is the relative rate of reaction for the given reaction.
2A + 9B → 7C + 4D
a) –rA = -9rB=7rC=–4rD
b) –rA =-rB/9=rC/7=rD/4
c) –rA =-rB/9=7rC=4rD
d) –rA = 9rB=-7rC=–4rD
View Answer

Answer: b
Explanation: Relative rate of reaction can be obtained from the ratio of stoichiometric co -efficient.

5. The units of rate constant of nth order is ___________
a) time-1
b) concentration(n-1)
c) time-1 concentration(1-n)
d) time-1 concentration(n-1)
View Answer

Answer: c
Explanation: General expression for the rate constant is time-1 concentration(1-n).

6. The unit for concentration equilibrium constant for the following reaction is _________
2A + 9B ←→7C + 4D
a) \((\frac{mol}{dm^3})\)2
b) \((\frac{mol}{dm^3})\)9
c) \((\frac{mol}{dm^3})\)-4
d) \((\frac{mol}{dm^3})\)-3
View Answer

Answer: d
Explanation: Concentration eqm constant for a reversible reaction is
aA + bB → cC + dD is
K = \(\frac{cC^c cD^d}{cA^a cB^b}\) unit is \((\frac{mol}{dm^3})\)c+d-a-b when it is applied to the above equation we get -3.

7. The overall reaction order for A + B → C + D is two. It implies that ______
a) reaction may be non-elementary and molecularity is two
b) reaction may be elementary and molecularity is two
c) reaction is non-elementary and molecularity is two
d) reaction is elementary and molecularity is two
View Answer

Answer: d
Explanation: Order is equal to molecularity when reaction is elementary.

8. Reaction corresponding to stoichiometric equation is called __________
a) Non-elementary
b) Elementary
c) Heterogeneous
d) Homogeneous
View Answer

Answer: b
Explanation: Elementary reactions are the ones with single reaction step and the reaction rate corresponds to stoichiometric equation.

9. The rate constant for a first order reaction depends on _____________
a) Pressure
b) Temperature
c) Concentration
d) Time
View Answer

Answer: b
Explanation: The reaction rate constant depends on temperature only.

10. The mlecularity of the following single step reaction is ___________
aA + bB → pP
a) a+b-p
b) a+b+p
c) a+b
d) a-p
View Answer

Answer: c
Explanation: The above single step reaction is an elementary reaction. Molecularity is the number of molecules participating in the reaction.

Sanfoundry Global Education & Learning Series – Chemical Reaction Engineering.

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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