MEDIUMMCQ SINGLEIChO (Chemistry Olympiad)Physical ChemistryMole _ Equivalent ConceptAtomic and Molecular Masses

If 1021 molecules are removed from 200mg of CO₂, then the number of moles of CO₂ left are

A.2.85 × 10–3✓ Correct

B.28.8 × 10–3

C.0.288 × 10–3

D.1.68 × 10–2

Explanation

Molar mass of 2 44 CO g Given mass=200 mg=0.2g Number of moles = 0.2 1 0.004545 mole 44 220 Since 23 6.023 10 x molecules are present in 1 mole of 2 CO . 21 21 23 2 1 1 10 molecules are present in = 1 10 6.023 10 = 0.0016603 mole Hence number of moles of CO left =0.00454-0.00166 x xx x 3 = 2.885 10 x Thus, correct option is (a). Percentage Composition ; Empirical & Molecular Formula

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