What is the molecular formula of this compound?

Question

Elemental ananalysis of a compound results in the following data

65.45 % C

5.49 % H

29.06 % O



5.51 g of the compound fills a 191.0 ml bottle with a pressure of 4846.2 mm Hg at a temperature of 23.7oC. What is the molecular formula of this compound ?

Answer 1

1) determine the mass of carbon, hydrogen and oxygen.
carbon: 65.45% x 4.13 g = 2.703 g
hydrogen: 5.49% x 4.13 g = 0.227 g
oxygen: 29.06% x 4.13 g = 1.200 g

2) convert to moles.
carbon: 2.703 / 12 = 0.225 mol
hydrogen: 0.27 / 1 = 0.227 mol
oxygen: 1.200 / 16 = 0.0750 mol

3) divide each molar amount by the lowest value to obtain small integers
carbon: 0.225 / 0.075 = 3
hydrogen: 0.227 / 0.075 = 3
oxygen: 0.075 / 0.075 = 1

The empirical formula of the substance is (C3H3O)k
The atomic masses add up to 55. To find k we need the molar mass of the compound. Use PV=nRT and plug in the data given *in the correct SI units*. Solve for n the number of moles in the sample. You problably find 5.51/55 or 5.51/110 so that k=1 or 2

Answer 2

sodium chloride and other ionic compounds form a crystal lattice with all + ions surrounded by - ions. So NaCl is a formula unit or unit cell, Ionic compounds do not form molecules. The formula tells how many of Na and Cl there are in one unit.

Answer 3

soda pop, or wine?
something carbonated?

Answer 4

DYOH