Which of the following contain the same number of atoms? (Given : Molar mass in g mol-1 of H, He, O and S are 1, 4, 16 and 32 respectively) Choose the correct answer from the options given below :
- A and B only
- B and C only
- C and D only
- A, C and E only
Answer
(4) A, C and E only
Solution
Number of atoms ∝ moles of atoms = moles of molecules × atomicity
A. 2 g O2: n = 232 = 0.0625 mol ⇒ atoms = 0.0625 × 2 = 0.125 mol
B. 4 g SO2: n = 464 = 0.0625 mol ⇒ atoms = 0.0625 × 3 = 0.1875 mol
C. 1400 mL O2 at STP: n = 1.422.4 = 0.0625 mol ⇒ atoms = 0.0625 × 2 = 0.125 mol
D. 0.05 L He at STP: n = 0.0522.4 = 2.23 10-3 mol (monoatomic) ⇒ atoms = 2.23 10-3 mol
E. 0.0625 mol H2 ⇒ atoms = 0.0625 × 2 = 0.125 mol
∴ A, C and E contain the same number of atoms (0.125 NA each).
Answer: (4)