In order to calculate the mass percent of nitrogen in Pb(NO3)2, first, list the molar mass of all elements.
Pb = 207.2 g/mol N = 14 g/mol O = 16 g/mol
Then, multiply each element to the number of each atom in the compound to get the mass contribution of each element, in this case:
Pb = (207.2 x 1) = 207.2 N = (14 x 2) = 28 O = (16 x 6) = 96
Add the resulting products to obtain the total molecular mass of the compound. This is equal to 331.2 g/mol. Finally, to get the mass percent of nitrogen, divide its mass contribution by the total molecular mass, as in, (28/331.2) x 100%. Thus, the mass percent of nitrogen in Pb(NO3)2 is 8.45%.
