What is the mass in grams of 2.57 × 10^{23} molecules of I_2?

• A. 86.8 g
• B. 86.8 g
• C. 0.87 g
• D. 108.8 g

Answer: (B)

Verified step by step guidance

1. Identify the given quantity: 2.57 \times 10^{23} molecules of I_2.
2. Recall that to find the mass from the number of molecules, you need to convert molecules to moles using Avogadro's number, which is 6.022 \times 10^{23} molecules per mole.
3. Calculate the number of moles of I_2 by dividing the given number of molecules by Avogadro's number: \(\text{moles} = \frac{2.57 \times 10^{23}}{6.022 \times 10^{23}}\).
4. Find the molar mass of I_2. Since iodine (I) has an atomic mass of approximately 126.9 g/mol, the molar mass of I_2 is \$2 \times 126.9$ g/mol.
5. Calculate the mass by multiplying the number of moles by the molar mass: \(\text{mass} = \text{moles} \times \text{molar mass}\).