Question

The characteristic odor of pineapple is due to ethyl butyrate, a compound containing carbon, hydrogen, and oxygen. combustion of 2.22 mg of ethyl butyrate produces 5.06 mg of co2 and 2.06 mg of h2o. what is the empirical formula of the compound? (type your answer using the format co2 for co2.)

Answer 1

Answer: C₃H₆O

Explanation:

1)  First, calculate the chemical composition, which you do using balance mass using the data given.

2) Data:

i) mass of ethyl butyrate: 2.22 mg

ii) mass of CO₂: 5.06 mg

iii) mass of H₂O: 2.06 mg

3) Solution

i) All the carbon in CO₂ produced was present in the ehtyl butyrate sample.

ii) The molar mass of CO₂ is 44.01 g/mol

iii) Use proportionality:

12.01 g C / 44.01 g CO₂ = x / 5.06 mg C  ⇒ x = 1.38 mg  C

iv) All the H in H₂O was present in the original sample of ethyl butyrate

v) The molar mass of H₂O is 18.015 g/mol

vi) Use proportionality

2.016 g H / 18.015 g H₂O = x / 2.06 mg H ⇒ x = 0.23 mg H

vii) Mass balance:

mass of O in the sample = mass of the sample - mass of H - mass of C

mass of O = 2.22 mg - 1.38 mg - 0.23 mg = 0.61 mg O.

viii) Composition:

C = 1.38 mg

H = 0.23 mg

O = 0.61 mg

Which in terms of composition is the same that:

C = 1.38 g

H = 0.23 g

O = 0.61 g

ix) Divide each by the molar atomic mass of the corresponding element, to obtain the number of moles:

C = 1.38 g / 12.01 g/mol = 0.115 mol

H = 0.23 g / 1.008 g/mol = 0.228 mol

O = 0.61 g / 16 g/mol = 0.0381 mol

x) Divide each by the least number of moles to obtain mole proportion

C = 0.115 / 0.0381 = 3.02 ≈ 3

H = 0.228 / 0.0381 = 1.98 ≈ 5.98 ≈ 6

O = 0.0381 / 0.0381 = 1

xi) Therefore the empirical formula searched is C₃H₆O.