Q1. The substance generally used in the tip of safety match stick is
(a) Red phosphorus
(b) Sodium
(c) Yellow phosphorus
(d) Antimony trisulphide
(UPSC Prelims 1980)
Answer: (d)
Explanation: Antimony trisulphide is commonly used in the match head along with oxidizing agents. It helps in ignition when struck against the friction surface, which typically contains red phosphorus.
Q131. Assertion: Alkalies are used for washing utensils.
Reason: Alkalies are readily soluble in water.
(a) if A and R both are correct and R is the correct explanation of A
(b) if A and R both are correct but R is not the correct explanation of A
(c) if A is correct and R is incorrect
(d) if A is incorrect and R is correct
(UPSC Prelims 1986)
Answer: (a) if A and R both are correct and R is the correct explanation of A
Explanation: Alkalies, such as sodium hydroxide, are commonly used in cleaning agents because they are highly soluble in water and can break down grease and food particles. Their solubility makes them effective for washing utensils, validating both the assertion and the reason.