how many molecules are 25 grams of NH3

Answer 1

Find moles of NH₃ and then convert to molecules using Avogadro's number (6.02x10²³ molecules/mole)

molar mass NH₃ = 14 + 3 = 17 g/mole

moles NH₃ = 25 g x 1 mole/17 g = 1.47 moles

molecules NH₃ = 1.47 moles x 6.02x10²³ molecules/mole = 8.9x10²³ molecules of NH₃ (to 2 sig. figs.)