Apentix/AP Chemistry/Unit 1: Atomic Structure and Properties/Question

AP Chemistrymediummcq1 pt

Which sample contains more atoms: 1.0 g of H₂ or 1.0 g of He?

A.H₂, because its lower molar mass gives more moles

B.He, because helium atoms are heavier

C.They contain equal numbers of atoms

D.H₂, because its molecules contain two atoms

Explanation

Core Concept

1.0 g H₂ = 0.50 mol of molecules, each with 2 atoms, so 1.0 mol of H atoms. 1.0 g He = 0.25 mol of atoms. Hydrogen has four times the atoms because each mole of H₂ contributes two atoms and H₂'s molar mass is half He's.

Correct Answer

AH₂, because its lower molar mass gives more moles

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