What is the percentage by mass of nitrogen in nitroglycerin?

Sure, to find the percentage by mass of nitrogen in nitroglycerin, we need to follow these steps:

1. First, we need to know the molecular formula of nitroglycerin, which is C3H5N3O9.

2. Next, we need to calculate the molar mass of nitroglycerin. To do this, we add up the molar masses of all the atoms in the formula. The molar mass of carbon (C) is approximately 12.01 g/mol, hydrogen (H) is approximately 1.01 g/mol, nitrogen (N) is approximately 14.01 g/mol, and oxygen (O) is approximately 16.00 g/mol. So, the molar mass of nitroglycerin is (312.01 g/mol) + (51.01 g/mol) + (314.01 g/mol) + (916.00 g/mol) = 227.09 g/mol.

3. Then, we need to find the total mass of nitrogen in the formula. Since there are three nitrogen atoms, the total mass of nitrogen is 3*14.01 g/mol = 42.03 g/mol.

4. Finally, we find the percentage by mass of nitrogen in nitroglycerin by dividing the total mass of nitrogen by the molar mass of nitroglycerin and then multiplying by 100. So, the percentage by mass of nitrogen in nitroglycerin is (42.03 g/mol / 227.09 g/mol) * 100 = 18.5%.

So, the percentage by mass of nitrogen in nitroglycerin is approximately 18.5%.