Question

For a chemical reaction to occur

• A. the reacting molecules must collide with each other
• B. reacting molecules should have sufficient energy at the time of the collision
• C. reacting molecules must be properly oriented
• D. all of the above

Answer 1

The correct option is D

all of the above

The explanation for the correct option: (D)

According to collision theory:

1) Chemical reactions can occur only upon collisions between reactant molecules.
2) However all the collisions do not lead to the formation of products. Otherwise, all the reactions could occur within a fraction of a second since there are millions of collisions possible. The minimum amount of energy required by the colliding molecules to yield the products is called Threshold Energy (ET).
The reactant molecules must cross this energy barrier to be converted to products.
4) The energy possessed by the normal reactant molecules under STP conditions is called ‘Average Energy’.
The difference between threshold energy and average energy of the reacting molecules is called Activation energy.

The explanation for the incorrect options:

(a) According to collision theory the reacting molecules must collide with each other for a chemical reaction to occur. This is true but other options are also true.

(b) All the above options are required for a chemical reaction to occur.

(c) According to collision theory for a chemical reaction to occur reacting molecules must be properly oriented. This is true but other options are also true.

Conclusion: Hence option (d) is correct - All the above.