What is the mass of 9.00 × 10^{22} molecules of NH_3?

• A. 1.50 g
• B. 2.55 g
• C. 0.75 g
• D. 4.50 g

Answer: (B)

Verified step by step guidance

1. Identify the given information: the number of molecules of NH_3 is \$9.00 \times 10^{22}$ molecules.
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 NH_3 by dividing the given number of molecules by Avogadro's number: \(\text{moles} = \frac{9.00 \times 10^{22}}{6.022 \times 10^{23}}\).
4. Determine the molar mass of NH_3 by adding the atomic masses of nitrogen (N) and hydrogen (H): \(\text{molar mass} = 14.01 + 3 \times 1.008\) g/mol.
5. Calculate the mass of NH_3 by multiplying the number of moles by the molar mass: \(\text{mass} = \text{moles} \times \text{molar mass}\).