Which of the following samples contains the greatest number of atoms?

• A. 18 g of H2O
• B. 44 g of CO2
• C. 12 g of He
• D. 32 g of O2

Answer: (C)

Verified step by step guidance

1. Identify the molar mass of each substance: calculate the molar mass of H\_2O, CO\_2, He, and O\_2 using the atomic masses from the periodic table.
2. Calculate the number of moles in each sample by dividing the given mass by the molar mass: use the formula \(\text{moles} = \frac{\text{mass}}{\text{molar mass}}\) for each substance.
3. Determine the total number of atoms in each sample: for molecular substances like H\_2O, CO\_2, and O\_2, multiply the number of moles by Avogadro's number (\$6.022 \times 10^{23}$) and then by the number of atoms per molecule (e.g., 3 atoms for H\_2O, 3 atoms for CO\_2, 2 atoms for O\_2). For helium (He), which is monoatomic, multiply the moles by Avogadro's number directly.
4. Compare the total number of atoms calculated for each sample to determine which one contains the greatest number of atoms.
5. Conclude by identifying the sample with the highest total atom count based on your calculations.