Question

Assertion (A): On burning magnesium in oxygen, the mass of magnesium oxide formed is equal to the total mass of magnesium and oxygen.
Reason (R): In a chemical substance, the elements are always present in a definite proportion
a) Both A and R are true and R is the correct explanation of A
b) Both A and R are true but R is not the correct explanation of A
c) A is true but R is false
d) A is false but R is true

Answer 1

Answer:

B) both A and R correct but R is not the correct explanation of q

this is govern by rule mass can neither be created nor destroyed in a chemical reaction

Answer 2

b) Both A and R are true but R is not the correct explanation of A is correct about given statements.

• As per the law of conservation of mass, assertion is true. This is because the combination reaction produces only magnesium oxide.
• So, combined mass of reactant side will be equal to the mass of compound on product side.
• According to law of definite proportion, irrespective of the source of magnesium oxide, the number of atoms of magnesium and oxygen will remain constant.