Carboxylic Acids - Evaluative Prep.

I am creating these cards as preperation for a final evaluative task I am completing as part of my AS chemistry coursework.

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What are carboxylic acids?

Carboxylic acids are compounds which contain a -COOH group.


Methanoic Acid, Ethanoic Acid, Propanoic Acid, Butanoic Acid, Pentanoic Acid.

Naming Carboxylic Acids:

The name counts the total number of carbon atoms in the longest chain - including the one in the -COOH group. If you have side groups attached to the chain, notice that you always count from the carbon atom in the -COOH group as being number 1.

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Salts of Carboxylic Acids

Why are carboxylic acids acidic? - Because of the hydrogen in their OH group. When the acids form salts this H+ is lost and replaced by a metal compound.

- In solution in water, a hydrogen ion is transferred from the -COOH group to a water molecule. For example, with ethanoic acid, you get an ethanoate ion formed together with a hydroxonium ion, H3O+.

- This reaction is reversible and, in the case of ethanoic acid, no more than about 1% of the acid has reacted to form ions at any one time.

These are therefore weak acids.


This equation is often simplified to:


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pH of carboxylic acids

The pH depends on both the concentration of the acid and how easily it loses hydrogen ions from the -COOH group.

Ethanoic acid is typical of the acids where the -COOH group is attached to a simple alkyl group. Typical lab solutions have pH's in the 2 - 3 range, depending on their concentrations.

Methanoic acid is rather stronger than the other simple acids, and solutions have pH's about 0.5 pH units less than ethanoic acid of the same concentration.

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Infrared Spectometry for Carboxylic Acids


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Reactions of Carboxylic Acids

Carboxylicacids react in the same wayas dilute mineral acids.
1. The reaction of carboxylicacids with alkalis.

Carboxylic acids are neutralised by alkalis, for example.

methanoic acid+ sodium hydroxide arrow ( sodium methanoate + water.
HCO2H(aq) + NaOH(aq) arrow ( HCO2Na(aq) + H2O(l)

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2. The reaction ofcarboxylicacids with carbonates.

Carboxylic acids are neutralised by carbonates, for example

ethanoic acid + sodiumcarbonate arrow ( sodium ethanoate + carbon dioxide + water.
2CH3CO2H(aq) + Na2CO3(s) arrow ( 2CH3CO2Na(aq) + CO2(g) + H2O(l)

butanoic acid + zinccarbonate arrow ( zinc butanoate +carbon dioxide + water.
2C3H7CO2H(aq) + ZnCO3(s) arrow ( (C3H7CO2)2Zn(aq) + CO2(g) + H2O(l)

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The reaction of carboxylicacids with metals.
magnesium + ethanoic acid - magnesium ethanoate + hydrogen
Mg(s) + 2CH3CO2H(aq) (CH3CO2)2Mg(aq) + H2(g)

zinc + propanoic acid - zincpropanoate + hydrogen.
Zn(s) + 2C2H5CO2H(aq) (C2H5CO2)2Zn(aq) + H2(g)

4. The reaction of Carboxylic acids with alcohols.
Carboxylic acids will react with alcoholsto form esters

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