AQA A Level Chemistry復習筆記3.1.2 Types of Formulae
Types of Formulae
- The?general formula?is a formula that represents a?homologous series?of compounds using letters and numbers
- Eg. the general formula of alkanes is CnH2n+2
- A homologous series is a group of organic compounds that have the same functional group, the same general formula and the same chemical properties
- The?structural formula?is a formula that shows how the atoms are bonded to each carbon atom in a molecule
- The?displayed formula?is a 2D representation of an organic molecule showing?all?its atoms (by their?symbols) and their bonds (by single, double or triple bonds)
- The?skeletal formula?is a simplified displayed formula with all the carbon and hydrogen (C-H) bonds removed
Overview of the Formulae of Organic Compounds Table
Worked Example
Drawing skeletal formulae of molecules
Draw the skeletal formula of the following molecules:
- CH3(CH2)3OH
- (CH3)2CHCH2OH
- CH3CH2OCH2CH3
Answer:
Worked Example
Drawing displayed formulae of molecules
Draw the displayed formula of the following molecules:
Answer
Molecular & Empirical Formulae
- The?molecular formula?shows the number and type of each atom in a molecule
- Eg. the molecular formula of ethanoic acid is C2H4O2
- The?empirical formula?shows the simplest whole number ratio of the elements present in one molecule of the compound
- Eg. the empirical formula of ethanoic acid is CH2O
Worked Example
Deducing molecular & empirical formulaeDeduce the molecular and empirical formula of the following compounds:
Answer
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