Which of the following samples contains a total of 9.0 × 10^{23} atoms?

• A. 2.0 moles of carbon dioxide (CO_2)
• B. 1.5 moles of helium (He)
• C. 0.5 moles of oxygen gas (O_2)
• D. 3.0 moles of sodium chloride (NaCl)

Answer: (B)

Verified step by step guidance

1. Recall that 1 mole of any substance contains Avogadro's number of particles, which is approximately \$6.022 \times 10^{23}$ atoms or molecules.
2. Calculate the total number of atoms in each sample by multiplying the number of moles by Avogadro's number and considering the number of atoms per molecule or formula unit.
3. For \(\mathrm{CO_2}\): Each molecule contains 3 atoms (1 carbon + 2 oxygen). So, total atoms = moles of \(\mathrm{CO_2}\) \times Avogadro's number \times 3.
4. For \(\mathrm{He}\): Each atom is a single atom, so total atoms = moles of \(\mathrm{He}\) \times Avogadro's number.
5. For \(\mathrm{O_2}\): Each molecule contains 2 atoms, so total atoms = moles of \(\mathrm{O_2}\) \times Avogadro's number \times 2. For \(\mathrm{NaCl}\): Each formula unit contains 2 atoms (1 Na + 1 Cl), so total atoms = moles of \(\mathrm{NaCl}\) \times Avogadro's number \times 2. Compare these totals to \$9.0 \times 10^{23}$ atoms to find the correct sample.