This set of Engineering Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Molecularity of a Reaction”.
1. Molecularity of a reaction is equal to the total number of _____________
a) Products formed in the elementary step
b) Reactants taking part in elementary step
c) Reactants and products in the elementary step
d) Reactants and products in the final step
View Answer
Explanation: Molecularity of a reaction is equal to the total number of reactants taking part in an elementary step. It is defined as the number of molecules or ions that participate in the rate determining step.
2. The molecularity of a multi-step reaction does not make any sense.
a) True
b) False
View Answer
Explanation: The molecularity of a multi-step reaction does not make any sense. The molecularity of each step is different. And molecularity of one step can only be determined at a time.
3. The elementary processes with molecularity greater than ________ are not known.
a) 1
b) 2
c) 3
d) 0
View Answer
Explanation: The elementary processes with molecularity greater than three are not known. There is no such reaction which has the molecularity greater than three.
4. Which of the following statement is incorrect about the molecularity of a reaction?
a) It is a theoretical concept
b) Each step of a multi-step reaction has a unique molecularity
c) It is equal to the total number of reactants taking part in elementary step
d) It can be zero, fractional or integer
View Answer
Explanation: Molecularity is always a whole number. It can be neither zero nor fractional. All the other options are correct.
5. Which of the following factor does not effect the rate of reaction?
a) Concentration of the reactant
b) Temperature
c) Pressure
d) Effect of catalyst
View Answer
Explanation: The reaction rate does not depend upon the pressure. It only depends upon the concentration of the reactant, temperature and effect of catalyst.
6. The effective collisions between the reactant molecules at higher temperatures ___________
a) Increase
b) Decrease
c) Remains same
d) First increase then decrease
View Answer
Explanation: The effective collisions between the reactant molecules at higher temperatures increase. At higher temperature randomness increases and molecules moves with a faster velocity which results in more collision between the reactants.
7. Concentration of the reactants is __________ proportional to the number of collisions and _________ proportional to the reaction rate.
a) Directly, inversely
b) Directly, directly
c) Inversely, directly
d) Inversely, inversely
View Answer
Explanation: Concentration of the reactants is directly proportional to the number of collisions and also directly proportional to the reaction rate. The more the collision, more will be the reaction rate and hence more will be the concentration of reactants.
8. The reaction rate is greatly influenced by ___________
a) Nature of bond in the reactant molecules
b) Strength of bond in the reactant molecules
c) Both nature and strength of the reactant molecules
d) It does not depend on either nature or strength of the reactant molecules
View Answer
Explanation: The reaction rate is greatly influenced by both nature and strength of the reactant molecules. Reactants are the major factor that affects the rate of the reaction.
9. The reactions register an increase in rates in the presence of radiations of specific wavelengths.
a) True
b) False
View Answer
Explanation: The reactions register an increase in rates in the presence of radiations of specific wavelengths.
10. Select the correct option from the following option.
a) Catalyst is used to increase the rate of reaction by altering chemically during the course of reaction
b) Catalyst is used to decrease the rate of reaction by altering chemically during the course of reaction
c) Catalyst is used to increase the rate of reaction and remains unaltered chemically during the course of reaction
d) Catalyst is used to decrease the rate of reaction and remains altered chemically during the course of reaction
View Answer
Explanation: Catalyst is used to increase the rate of reaction and remains unaltered chemically during the course of the reaction. With a catalyst, reactions occur faster and require less activation energy. Because catalysts are not consumed in the catalyzed reaction, they can continue to catalyze the reaction of further quantities of reactant.
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