Final answer:
The mass of 8.50 x 10²² molecules of NH₃ is calculated to be 2.403 grams, using Avogadro's number and the molar mass of NH₃.
Step-by-step explanation:
To calculate the mass of 8.50 x 10²² molecules of NH₃, you need to use Avogadro's number (6.022 x 10²³ molecules/mol) and the molar mass of NH₃. Since one mole of any substance contains Avogadro's number of entities (molecules, in this case), we can determine the number of moles first. The molar mass of NH₃ is 17.03 g/mol, calculated by adding together the atomic masses of nitrogen (14.01 g/mol) and three hydrogen atoms (3 x 1.01 g/mol).
The number of moles of NH₃ is obtained using the formula:
moles = (number of molecules) / (Avogadro's number)
moles NH₃ = (8.50 x 10²² molecules) / (6.022 x 10²³ molecules/mol) = 1.411 x 10^-1 mol
Now, by multiplying the moles of NH₃ by its molar mass, we'll get the mass:
mass NH₃ = moles NH₃ x molar mass NH₃
mass NH₃ = (1.411 x 10^-1 mol) x (17.03 g/mol) = 2.403 g
Therefore, the mass of 8.50 x 10²² molecules of NH₃ is 2.403 grams.