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ICSE Class 10 Chemistry Question 6 of 23

Model Paper 1 — Question 11

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11
Question

Question 1(xi)

Assertion (A): The RMM of a gas is 64, then its vapour density is 32.

Reason (R): RMM is twice the vapour density.

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
Answer

Both A and R are true and R is the correct explanation of A.

Reason — Vapour density (V.D.) is related to relative molecular mass by:

V.D.= Relative molecular mass2\text{V.D.} = \dfrac{\text{ Relative molecular mass}}{2}

Substituting the given value:

V.D.=622=32\text{V.D.} = \dfrac{62}{2} = 32

Thus the assertion is correct. Because the reason states the same relationship—“The RMM is twice the vapour density”—it correctly explains why the vapour density is 32.