A 5.00 g of a certain Compound X, known to be made of carbon, hydrogen and perhaps oxygen, and to have a molecular molar mass of 78./gmol, is burned completely in excess oxygen, and the mass of the products carefully measured:

product mass

carbon dioxide 16.93g

water 3.46g

Use this information to find the molecular formula of X.

C6H6

Explanation:

Step 1:

Data obtained from the question. This include the following:

Mass of the compound = 5g

Molar mass of the compound = 78g/mol

Mass of CO2 = 16.93g

Mass of H2O = 3.46g

Step 2:

Determination of the mass of carbon, hydrogen and oxygen present ij the compound. This can be obtained as follow:

Molar mass of CO2 = 12 + (2x16) = 44g/mol

Mass of C = 12/44 x 16.93 = 4.62g

Molar mass of H2O = (2x1) + 16 = 18g/mol

Mass of H = 2/18 x 3.46 = 0.38g

Mass of O = 5 - (4.62 + 0.38) = 0

Step 3:

Determination of the empirical formula of the compound.

C = 4.62g

H = 0.38g

Divide by their molar mass

C = 4.62/12 = 0.385

H = 0.38/1 = 0.38

Divide by the smallest

C = 0.385/0.38 = 1

H = 0.38/0.38 = 1

Therefore, the empirical formula of the compound is CH.

Step 4:

Determination of the molecular formula of the compound.

The molecular formula of a compound is simply a multiple of the empirical formula.

The molecular formula = > [CH]n

[CH]n = 78

[12 + 1]n = 78

13n = 78

Divide both side by 13

n = 78/13

n = 6

The molecular formula = > [CH]n

=> [CH]6

=> C6H6.

Therefore, the molecular formula of the compound is C6H6.