Question

Which of the following pairs does not share the same empirical formula?
CH2O and C3H6O3

PbCl2 and PbCl4

NO2 and N2O4

C3H12 and CH4

Answer 1

I prefer to use intuition to solve certain empirical formula problems, even though there are mathematical solutions. If the empirical formula is 1:1, then use the atomic weights and your intuition to figure out a formula.

78.06 g/mol = CnHn

Let's try 6 for n, arbitrarily speaking.

C6H6 = (12*6) + (1*6) = 78.06 roughly. This formula is for benzene.

For the second one, take the molecule with the fewest substituents and compare it to the one with more. If they have a common multiple, then they are an empirical pair.

For example, if i multiplied CH2O by 3, I'd get C3H6O3. Therefore they are a pair. However, if I multiply PbCl2 by 2 I'd get Pb2Cl4, which is not what is shown. So the answer is B.

Hope this helps. Best of luck

Answer 2

@Forthegraduation