Compare total atoms by multiplying moles of compound by atoms per molecule

Steps:

• Recall 1 mole of any substance contains 6.022 × 10²³ particles (Avogadro's number).
• Calculate atoms per molecule: H₂O (3), CO₂ (3), CH₄ (5), HCl (2).
• Compute total moles of atoms: multiply moles of compound by atoms per molecule.
• Compare: A (1.5), B (3), C (5), D (4)—C is highest.

Why C is correct:

• Methane (CH₄) has 5 atoms per molecule; 1.0 mol yields 5 moles of atoms, the maximum per Avogadro's number.

Why the others are wrong:

• A: 0.5 mol H₂O has 3 atoms/molecule, totaling 1.5 moles of atoms—least.
• B: 1.0 mol CO₂ has 3 atoms/molecule, totaling 3 moles of atoms—fewer than C.
• D: 2.0 mol HCl has 2 atoms/molecule, totaling 4 moles of atoms—still less than C.

Final answer: C