Question

One method for determining the identity of an unknown organic compound is through combustion analysis. A sample of an unknown substance is burned, and the amounts of water and carbon dioxide produced can be used to find the relative amounts of carbon, hydrogen, and oxygen. These devices can be modified to determine the composition of inorganic compounds as well. A combustion analysis shows that an unknown sample of gas is made of 85.5% carbon and 14.3% hydrogen. What is the empirical formula of the compound

Answer 1

Answer:

Empirical formula: CH₂

Explanation:

We need to find the empirical formula of a compound that has carbon and hydrogen.

To find the empirical formula of any compound, if we have the mass or mass percent, we should follow 3 steps:

1. Calculate the moles, dividing by the atomic weight.

The atomic weight for carbon and hydrogen are 12 g/mol and 1 g/mol, so, doing the division we have:

C = 85.5 / 12 = 7.125

H = 14.3 / 1 = 14.3

2. Determine the number of atoms of each element in the formula

To do this, we just divide the previous moles by the lowest quantity we obtain. In this case, the carbon:

C = 7,125 / 7,125 = 1

H = 14,3 / 7,125 = 2

This means we have 1 atom of carbon and 2 atoms of hydrogen.

3. Write the empirical formula with the previously obtained atoms

Now that we obtained the atoms of each element, we just write the empirical formula with these numbers:

C₁H₂  but we can neglect the number one so:

Empirical formula: CH₂

Hope this helps