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Edexcel IAL Chemistry 20.1 empirical, molecular and structural formulae

Work from the evidence in order: convert combustion masses to moles, use spectra and functional-group tests, then check the final structure against the molecular formula.

Syllabus
First assessment 2019
Course
Chemistry YCH11
Level
A2

Exam points

  • Calculate empirical formulae from CO2, H2O and oxygen-by-difference data.
  • Use functional-group tests and IR, MS, 13C NMR or proton NMR to justify structures.
  • Deduce structural formulae from empirical formulae, molecular formulae and test evidence.

20.1—Deduce the empirical formulae, molecular formulae and structural formulae from data drawn from combustion analysis, element question 1

[Maximum number: 4]

This question concerns six isomers each with the molecular formula C5H10O2\mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}_{2}.

Isomer F is a neutral compound that smells of pears.

It can be formed by the reaction between compounds V and W in the presence of concentrated sulfuric acid.

Compound V has an absorption in its infrared spectrum at 1720 cm−11720 \mathrm{~cm}^{-1} and a broad absorption around 3050 cm−13050 \mathrm{~cm}^{-1}.

Compound W can be formed directly from propanal.

Identify, by name or formula, compounds V, W and F.

Justify your answer by using all the available information.

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