Question

A 425.00-gram sample of a compound decomposes into 196.01 grams of carbon, 41.14 grams of hydrogen, 130.56 grams of oxygen, and 57.29 grams of silicon. Experiments have shown the compound has a molecular weight of 208.329. What is the molecular formula?

Answer 1

Answer:

C₈H₂₀O₄Si

Explanation:

The moles of each atom (Using atomic weight) are:

C: 196.01g × (1mol / 12.01g) = 16.32 moles of C

H: 41.14g × (1mol / 1.01g) = 40.73 moles of H

O: 130.56g × (1mol / 16g) = 8.16 moles of O

Si: 57.29g × (1mol / 28.09g) = 2.04 moles of Si

Dividing in the number of moles of Si to obtain the simplest ratio:

C: 16.32mol C / 2.04mol: 8

H: 40.73mol H / 2.04mol: 20

O: 8.16 mol O / 2.04mol: 4

Si: 2.04mol / 2.04mol: 1

Thus, empirical formula of the compound is:

C₈H₂₀O₄Si.

Molar mass for this formula is:

12.01g/mol × 8 + 1.01g/mol × 20 + 16g/mol × 4 + 28.09g/mol × 1 =

208.37 g/mol ≈ Molecular weight obtained in the experiment.

Thus, molecular formula of the compound is:

C₈H₂₀O₄Si