Question

The molecular formula for a compound with a molar mass of 180.18g that contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass is

Answer 1

Answer:

C6H12O6

Explanation:

First you need to find the empirical formula by the percents that they're giving you. You assume that is 100 grams and if for example you have 40% of carbon you will have 40 grams of carbon.

1.Find the number of moles of each atom

C: 40g÷12g/mol= 3.33 mol

H: 6.7g÷1g/mol= 6.7 mol

O: 53.3g÷16g/mol= 3.33 mol

You divide all ratios by the minimum ratio and you obtain the empirical formula

CH2O

Since you're given the molar mass, you now have to find the molar mass of CH2O by adding the molar mass of each element present and repeated in the compound.

CH2O= 30g/mol

Now you know that the molar mass of the molecular formula we are looking for is 180.18 g/mol, and since the empirical formula is the molecular formula in its smaller ratio, by logic you can say that:

180.18g/mol ÷ 30g/mol= 6

So, you now know that the empirical formula is being multiplied by a factor of 6 to reach a compound with a molar mass of 180.18g/mol, so you multiply each subscript of the empirical formula by 6 obtaining:

C6H12O6