a. How many atoms of hydrogen are in 25.0 g of ammonia (NH3)? Use the format 6.02E+23 for 6.02 x 1023

b. How many atoms of nitrogen are in the same amount of ammonia? Use the molar mass to two decimal places found on the periodic table in the front of your text.

mols NH3 = grams/molar mass

mols H = 3x mols NH3 because there are 3 atoms of H for every molecule of NH3.
Then atoms H = mols H x 6.02E23.

You try b part. Post your work if you run into trouble.