Question

Compound X has a molar mass of 135.13 and the following composition: element mass % carbon 44.44% hydrogen 3.73% nitrogen 51.83% Write the molecular formula of X.

Answer 1

Hello!

First, let's see what a molar mass is. A molar mass is how much a mole weighs, or how much 6.02214076×10²³ of an element weighs.

Now, let's find the molar mass of each of these three elements.

Carbon: 12.0107 g/mol

Hydrogen: 1.00784 g/mol

Nitrogen: 14.0067 g/mol

Now, see how much of the molar mass of compound x each of these contributes.

Carbon: 44.44% * 135.13 = 60.051772 g/mol

Hydrogen: 3.73% * 135.13 = 5.040349 g/mol

Nitrogen: 51.83% * 135.13 = 70.037879 g/mol

Finally, calculate how many atoms there are in the molecule. Do this my dividing the "how much they contribute to the molar mass" by the molar mass.

Carbon: 60.051772 / 12.0107 = 5

Hydrogen: 5.040349 / 1.00784 = 5

Nitrogen: 70.037879 / 14.0067 = 5

Therefore, we know that there are 5 Carbons, 5 hydrogens, and 5 nitrogens.

Put this all together to get the molecular formula: C5H5N5 (note that the numbers should be written as subscript)

Hope this helps!