2 g of hydrogen combines with 16 g of oxygen to form 18 g of water. Class 9

2 g of hydrogen combines with 16 g of oxygen to form 18 g of water. Class 9

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Question 1.

Assertion (A): 2 g of hydrogen combines with 16 g of oxygen to form 18 g of water.

Reason (R): According to Dalton’s Atomic Theory, atoms combine in a simple whole number ratio by mass to form compounds. Class 9

Choose the correct option:

(i) Both A and R are true, and R is the correct explanation of A.

(ii) Both A and R are true, but R is not the correct explanation of A.

(iii) A is true, but R is false.

(iv) A is false, but R is true.

Answer:

(ii) Both A and R are true, but R is not the correct explanation of A.

Assertion A is true: 2 g of hydrogen + 16 g of oxygen = 18 g of water (consistent with the Law of Conservation of Mass and the formula H₂O). Reason R is also true: Dalton's Atomic Theory does state that atoms combine in simple whole number ratios. However, R is not the correct explanation of A. Assertion A is explained by the Law of Conservation of Mass (total mass of reactants = total mass of products), not directly by the statement that atoms combine in simple whole number ratios by mass. The combining ratio in A is by number of atoms (2 hydrogen atoms to 1 oxygen atom), not by mass.