How many hydrogen atoms are present in 35.0 grams of hydrogen gas (H_2)?

• A. 6.02 × 10^{23} atoms
• B. 3.50 × 10^{24} atoms
• C. 2.10 × 10^{25} atoms
• D. 1.05 × 10^{25} atoms

Answer: (D)

Verified step by step guidance

1. Determine the molar mass of hydrogen gas (H\_2). Since each hydrogen atom has an atomic mass of approximately 1.00 g/mol, the molar mass of H\_2 is calculated as \$2 \times 1.00 = 2.00$ g/mol.
2. Calculate the number of moles of hydrogen gas in 35.0 grams using the formula: \(\text{moles} = \frac{\text{mass}}{\text{molar mass}} = \frac{35.0}{2.00}\) mol.
3. Find the number of molecules of H\_2 by multiplying the moles of H\_2 by Avogadro's number: \(\text{molecules} = \text{moles} \times 6.02 \times 10^{23}\) molecules/mol.
4. Since each molecule of H\_2 contains 2 hydrogen atoms, multiply the number of H\_2 molecules by 2 to get the total number of hydrogen atoms: \(\text{atoms} = \text{molecules} \times 2\).
5. Express the final answer in scientific notation to match the given options.