To calculate the number of molecules of NBr3 in 25.0 g of NBr3, we need to follow a few steps:
1. Determine the molar mass of NBr3:
- N: atomic mass = 14.01 g/mol
- Br: atomic mass = 79.90 g/mol
- NBr3 has one nitrogen atom and three bromine atoms, so the molar mass of NBr3 is:
(1 * N) + (3 * Br) = (1 * 14.01 g/mol) + (3 * 79.90 g/mol) = 252.71 g/mol
2. Calculate the number of moles of NBr3 using the given mass and molar mass:
- Moles = Mass / Molar mass
- Moles = 25.0 g / 252.71 g/mol
- Moles ≈ 0.099 mol (rounded to three significant figures)
3. Finally, calculate the number of molecules using Avogadro's number:
- Avogadro's number (NA) = 6.022 × 10^23 molecules/mol
- Number of molecules = Moles * NA
= 0.099 mol * (6.022 × 10^23 molecules/mol)
≈ 5.95 × 10^22 molecules
Therefore, there are approximately 5.95 × 10^22 molecules of NBr3 in 25.0 g NBr3.