(f) Carboxylic acids

4:35 (Triple only) understand how to draw structural and displayed formulae for unbranched- chain carboxylic acids with up to four carbon atoms in the molecule, and name each compound

The four simplest carboxylic acids are methanoic acid, ethanoic acid, propanoic acid and butanoic acid.

 

Methanoic acid

Displayed formula:Image result for methanoic acid

Molecular formula: CH₂O₂

Structural formula: HCOOH

 

Ethanoic acid

Displayed formula:

Molecular formula: C₂H₄O₂

Structural formula: CH₃COOH

 

Propanoic acid

Displayed formula:Image result for propanoic acid

Molecular formula: C₃H₆O₂

Structural formula: CH₃CH₂COOH

 

Butanoic acid

Displayed formula:Image result for butanoic acid

Molecular formula: C₄H₈O₂

Structural formula: CH₃CH₂CH₂COOH

4:36 (Triple only) describe the reactions of aqueous solutions of carboxylic acids with metals and metal carbonates

Dilute carboxylic acids react with metals in the same way as other dilute acids (e.g. hydrochloric acid) only more slowly.

For example, dilute ethanoic acid reacts with magnesium with a lot of fizzing to produce a salt and hydrogen, leaving a colourless solution of magnesium ethanoate:

magnesium      +      ethanoic acid      →      magnesium ethanoate      +      hydrogen

Mg (s)         +         2CH₃COOH (aq)         →         (CH₃COO)₂Mg (aq)         +         H₂ (g)

 

Dilute carboxylic acids react with metal carbonates as they do with other acids, to give a salt, carbon dioxide and water.

For example, dilute ethanoic acid reacts with sodium carbonate with a lot of fizzing to produce a salt,  carbon dioxide and water, leaving a colourless solution of sodium ethanoate:

sodium carbonate      +      ethanoic acid      →      sodium ethanoate      +      carbon dioxide      +      water

Na₂CO₃ (s)         +         2CH₃COOH (aq)         →         2CH₃COONa (aq)         +         CO₂ (g)         +         H₂O (l)

 

As can be seen in the examples above the charge on the ethanoate ion is -1.

 

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Section 1: Principles of chemistry

      a) States of matter

      b) Atoms

      c) Atomic structure

     d) Relative formula masses and molar volumes of gases

     e) Chemical formulae and chemical equations

     f) Ionic compounds

     g) Covalent substances

     h) Metallic crystals

     i) Electrolysis

 Section 2: Chemistry of the elements

     a) The Periodic Table

     b) Group 1 elements: lithium, sodium and potassium

     c) Group 7 elements: chlorine, bromine and iodine

     d) Oxygen and oxides

     e) Hydrogen and water

     f) Reactivity series

     g) Tests for ions and gases

Section 3: Organic chemistry

     a) Introduction

     b) Alkanes

     c) Alkenes

     d) Ethanol

Section 4: Physical chemistry

     a) Acids, alkalis and salts

     b) Energetics

     c) Rates of reaction

     d) Equilibria

Section 5: Chemistry in industry

     a) Extraction and uses of metals

     b) Crude oil

     c) Synthetic polymers

     d) The industrial manufacture of chemicals