A compound is found to contain 16.66 grams of carbon and 3.49 grams of hydrogen. a. Find the empirical formula. (C2H5) b. The molar mass is 87. Find

Question

A compound is found to contain 16.66 grams of carbon and 3.49 grams of hydrogen.
a. Find the empirical formula. (C2H5)







b. The molar mass is 87. Find the molecular formula: (C6H15)

Answer 1

moles C = 16.66 g C x 1 mole/12.011 g = 1.387 moles C

moles H = 3.49 g H x 1 mole/1.0079 g = 3.4626 moles H

Divide both by 1.387 to obtain 1 mole C and 2.5 moles H

Now multiply both by 2 in order to obtain whole numbers and you get C₂H₅ as the answer.

 

If you want the molecular formula given the molar mass of 87, it would be as follows:

molar mass of C₂H₅ = 29

87/29 = 3, so there are 3 empirical formulae in 1 molecular formula and the molecular formula is C₆H₁₅