# How can I find the molecular formula from molar mass?

You start by determining the empirical formula for the compound.

1. Determine the mass in grams of each element in the sample. If you are given , you can directly convert the percentage of each element to grams.

For example, a molecule has a molecular weight of 180.18 g/mol. It is found to contain 40.00% carbon, 6.72% hydrogen and 53.28% oxygen.

Convert the percentages to grams.

40.00 grams of carbon
6.72 grams of hydrogen
53.28 grams of oxygen

1. Determine the number of moles of each element by dividing its mass in grams by its molar mass (atomic weight in g/mol).

moles C = 40.00 g x 1 mol C/12.01 g/mol C = 3.33 moles C

moles H = 6.72 g x 1 mol H/1.01 g/mol H = 6.65 moles H

moles O = 53.28 g x 1 mol O/16.00 g/mol O = 3.33 moles O

1. Calculate the by dividing the number of moles of each element by the lowest number of moles to get the lowest whole number ratio.

C = 3.33/3.33 = 1.00
H = 6.65/3.33 = 2.00
O = 3.33/3.33 = 1.00

1. Use the whole number ratio of moles to determine the empirical formula. The whole number ratio for each element becomes its subscript.

Empirical formula is ##”C””H”_2″O”##

1. Determine the empirical formula weight.

Empirical formula weight = (1 x 12.01g/mol) + (2 x 1.01g/mol) + (1 x 16.00g/mol) = 30.02g/mol.

1. Divide the molar mass for the molecular formula by the empirical formula mass. The result determines how many times to multiply the subscripts in the empirical formula to get the molecular formula.

The molecular weight of this compound is 180.18g/mol.
180.18/30.02 = 6.002

Multiply each subscript in the empirical formula to get the molecular formula. The molecular formula is ##”C”_6″H”_12″O”_6″##.

1. Double check by calculating your molecular molar mass.
C = (6 x 12.01g/mol) = 72.06
H = (12 x 1.01g/mol) = 12.12
O = (16.00 x 6g/mol) = 96
Total: 180.18g/mol

## Calculate the price of your order

550 words
We'll send you the first draft for approval by September 11, 2018 at 10:52 AM
Total price:
\$26
The price is based on these factors:
Number of pages
Urgency
Basic features
• Free title page and bibliography
• Unlimited revisions
• Plagiarism-free guarantee
• Money-back guarantee
On-demand options
• Writer’s samples
• Part-by-part delivery
• Overnight delivery
• Copies of used sources
Paper format
• 275 words per page
• 12 pt Arial/Times New Roman
• Double line spacing
• Any citation style (APA, MLA, Chicago/Turabian, Harvard)

# Our guarantees

Delivering a high-quality product at a reasonable price is not enough anymore.
That’s why we have developed 5 beneficial guarantees that will make your experience with our service enjoyable, easy, and safe.

### Money-back guarantee

You have to be 100% sure of the quality of your product to give a money-back guarantee. This describes us perfectly. Make sure that this guarantee is totally transparent.

### Zero-plagiarism guarantee

Each paper is composed from scratch, according to your instructions. It is then checked by our plagiarism-detection software. There is no gap where plagiarism could squeeze in.

### Free-revision policy

Thanks to our free revisions, there is no way for you to be unsatisfied. We will work on your paper until you are completely happy with the result.