Chemistry MCQs
Topic Notes: Chemistry
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
1
Evaluate the following statements: Assertion (A) BHC is also known as gammexane or 666. Reason (R) BHC is synthesized by the reaction of benzene with chlorine in the presence of ultraviolet light.
Answer:
Both A and R are true, but R is not the correct explanation of A
BHC (Benzene Hexachloride) is indeed called gammexane or 666. It is prepared by the free-radical addition of chlorine to benzene under UV light. While both statements are factually correct, the name '666' refers to the molecular formula C6H6Cl6, and the reaction mechanism is the standard method of preparation, though the name origin is distinct from the synthesis method.
2
How many ozone molecules can be destroyed by a single chlorine free radical?
Answer:
100000
A single chlorine free radical can initiate a chain reaction that destroys a large number of ozone molecules. It is estimated that one chlorine free radical can destroy up to 100,000 ozone molecules, contributing to ozone depletion in the stratosphere.
3
What is the primary product when toluene undergoes a reaction with chlorine in the presence of sunlight?
Answer:
Benzyl chloride
In the presence of sunlight, toluene reacts with chlorine through a free radical mechanism, leading to the substitution of a hydrogen atom at the benzylic position. This results in the formation of benzyl chloride as the first major product.
4
Rancidity in oils and fats is due to
Answer:
Oxidation
Oxygen is eight times more soluble in fats than in water and it is the oxidation resulting from this exposure that is the primary cause of rancidity. Oxidation primarily occurs with unsaturated fats by a free radical-mediated process.