Question

C3H2N, 208.17g/mol molecular formula?

Answer 1

The empirical formula is listed as C3H2N, and the molecular weight of the compound is listed as 208.17 g/mol. A molecular formula is always a multiple of the empirical formula, and the molecular weight is also a multiple of the empirical weight. From the empirical formula, we can calculate the empirical weight. We are given the molecular weight so we can calculate this multiple. First, we will determine the weight of the empirical formula. Using a periodic table, we see the weight of C is 12.01 g/mol. The weight of H is 1.008 g/mol. The weight of N is 14.01 g/mol. The weight of the empirical formula then is: (3*C)+(2*H)+(N) = (3*12.01) + (2*1.008) + (14.01) g/mol. This is equal to 52.06 g/mol with rounding to the least precise digit (100th's place). We now take the molecular formula weight and divide it by the empirical formula weight (208.17/52.06) = 3.999. This number is close enough to 4 that we assume to the multiple to be 4. We take the empirical formula and multiple it by 4: 4(C3H2N) and get C12H8N4. This is the molecular formula.