What is the mass, in grams, of 8.50 × 10^{22} molecules of NH_3?

• A. 1.20 g
• B. 4.53 g
• C. 2.39 g
• D. 17.0 g

Answer: (C)

Verified step by step guidance

1. Identify the given quantity: 8.50 \times 10^{22} molecules of NH_3.
2. Recall that to convert molecules to moles, use Avogadro's number, which is 6.022 \times 10^{23} molecules per mole. The formula is: \(\text{moles} = \frac{\text{number of molecules}}{6.022 \times 10^{23}}\).
3. Calculate the number of moles of NH_3 by dividing 8.50 \times 10^{22} molecules by Avogadro's number.
4. Determine the molar mass of NH_3 by adding the atomic masses: N (14.01 g/mol) + 3 \times H (1.008 g/mol) = molar mass of NH_3.
5. Find the mass in grams by multiplying the number of moles by the molar mass: \(\text{mass} = \text{moles} \times \text{molar mass}\).