Question

The foul odor of rancid butter is due largely to butyric acid, a compound containing carbon, hydrogen, and oxygen. Combustion analysis of a 4.30-g sample of butyric acid pro- duces 8.59 g CO2 and 3.52 g H2O. Determine the empirical formula for butyric acid.

Answer 1

The answer to your question is: C₂H₄O

Step-by-step explanation:

Data

Butyric acid CxHyOz

mass = 4.30 g

mass CO2 = 8.59 g

mass H2O = 3.52 g

Empirical formula = ?

Molecular weight CO2 = 44g

Molecular weight H2O = 18 g

Reaction

CxHyOz + O2 ⇒ CO2 + H2O

Process

Find the mass and moles of carbon

44g of CO2 ------------- 12 g of C

8.59g of CO2 ---------- x

x = 2.34 g of C

12 g of C ----------------- 1 mol of C

2.34 g of C ------------ x

x = 0.195 moles of carbon

Find the moles and mass of hidrogen

18 g of H2O ------------- 2 g of H

3.52 g of H2O --------- x

x = 0.39 g of H

1 g of H ----------------- 1 mol of H

0.39 g of H --------------- x

x = 0.39 mol of H

Find the mass and moles of oxygen

Mass of O = 4.30 - 2.34 - 0.39

= 1.57 g

Moles of Oxygen

16 g of O ----------------- 1 mol

1.57 g of O ------------- x

x = 0.098 moles

Divide the number of moles by the lowest number

Carbon 0.195/0.098 = 1.98 ≈ 2

Hydrogen 0.39/0.098 = 3.97 ≈ 4

Oxygen 0.098/0.098 = 1

Finally

Empirical formula = C₂H₄O