More Lessons for IGCSE Chemistry
A series of free IGCSE Chemistry Activities and Experiments (Cambridge IGCSE Chemistry).
• Draw the structures of methanoic acid, ethanoic acid and propanoic acid.
• Describe the reactions of carboxylic acids.
• Explain why carboxylic acids are weak acids.
Hydrochloric acid is a strong acid as it fully ionises. Hydrochloric acid has a low pH.
Carboxylic acid are weak acids as they do not fully ionise. Carboxylic acids have a higher pH.
Carboxylic Acid Reactions
Ethanol and Ethanoic Acid
Ethanol is produced from ethene, a chemical produced from the fractional distillation of crude oil and involving cracking using a catalyst at high temperature and pressure. Ethanol can be made in two ways:
1. Hydration of Ethene
Ethene + steam → ethanol
C2H4 + H2O → C2H5OH
2. Fermentation of Glucose
Fermentation of sugar from standard crops like sugar cane and corn, under warm and anaerobic conditions.
sugar (glucose) → ethanol + carbon dioxide
C6H12O6 → 2C2H5OH + 2CO2
This process uses yeast as an enzyme.
Ethanol + oxygen → ethanoic acid + water
C2H5OH + O2 → CH3COOH + H2O
Ethanoic acid is also known as acetic acid or vinegar.
Carboxylic Acids - Reactions
• Ethanoic acid is a typical acid. It will turn litmus paper and universal indicator red.
Ethanoic acid reacts with metal to form hydrogen gas.
• Magnesium + ethanoic acid → magnesium ethanoate + hydrogen
Mg(s) + 2CH3COOH(aq) → (CH3COO)2Mg(aq) + H2(g)
• Ethanoic acid reacts with bases to form water in a neutralisation reaction.
Ethanoic acid + sodium hydroxide → sodium ethanoate + water
2CH3COOH(aq) + NaOH(aq) → CH3COO2Na(aq) + H2O(l)
• Ethanoic acid reacts with carbonates to form water and carbon dioxide.
Ethanoic acid + sodium carbonate → sodium ethanoate + water
2CH3COOH(aq) + Na2CO3(aq) → 2CH3COO2Na(aq) + CO2(g) + H2O(l)
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