To calculate the mass of 3 moles of ammonia, we can use its molar mass. The molar mass of ammonia (NH3) is approximately 17.04 g/mol. This value represents the mass of one mole of ammonia.

Now, to find the mass of 3 moles of ammonia, we simply multiply the molar mass by the number of moles:

Mass = Molar mass × Number of moles

Mass = 17.04 g/mol × 3 moles

Mass ≈ 51.12 grams

Therefore, the mass of 3 moles of ammonia is approximately 51.12 grams.