Which statement is true about the molar mass of chlorine gas (Cl_2)?

• A. The molar mass of Cl_2 is less than the molar mass of oxygen gas (O_2).
• B. The molar mass of Cl_2 is the same as that of a single chlorine atom.
• C. The molar mass of Cl_2 is approximately 70.90 g/mol.
• D. The molar mass of Cl_2 is approximately 35.45 g/mol.

Answer: (C)

Verified step by step guidance

1. Recall that the molar mass of a diatomic molecule like chlorine gas (Cl_2) is the sum of the molar masses of two chlorine atoms.
2. Find the atomic mass of a single chlorine atom, which is approximately 35.45 g/mol.
3. Calculate the molar mass of Cl_2 by multiplying the atomic mass of chlorine by 2: \(\text{Molar mass of Cl}_2 = 2 \times 35.45\ \text{g/mol}\).
4. Compare this value to the molar mass of oxygen gas (O_2), which is \$2 \times 16.00 = 32.00\ \text{g/mol}$, to understand the relative sizes.
5. Understand that the molar mass of Cl_2 is not the same as a single chlorine atom, but approximately double, which leads to the correct molar mass being about 70.90 g/mol.