Which compound has the greatest percentage by mass of nitrogen atoms?A.     N2H4B.     NH3C.     N2O4D.     NaNO3

To answer this question, we need to calculate the percentage by mass of nitrogen in each compound.

1. N2H4: The molar mass of N2H4 is (214.007) + (41.008) = 32.052 g/mol. The mass of nitrogen in this compound is 2*14.007 = 28.014 g/mol. So, the percentage by mass of nitrogen is (28.014 / 32.052) * 100 = 87.4%.

2. NH3: The molar mass of NH3 is 14.007 + (3*1.008) = 17.031 g/mol. The mass of nitrogen in this compound is 14.007 g/mol. So, the percentage by mass of nitrogen is (14.007 / 17.031) * 100 = 82.2%.

3. N2O4: The molar mass of N2O4 is (214.007) + (415.999) = 92.02 g/mol. The mass of nitrogen in this compound is 2*14.007 = 28.014 g/mol. So, the percentage by mass of nitrogen is (28.014 / 92.02) * 100 = 30.4%.

4. NaNO3: The molar mass of NaNO3 is 22.990 + 14.007 + (3*15.999) = 84.994 g/mol. The mass of nitrogen in this compound is 14.007 g/mol. So, the percentage by mass of nitrogen is (14.007 / 84.994) * 100 = 16.5%.

Therefore, the compound with the greatest percentage by mass of nitrogen atoms is N2H4.