Lesson 17C.1
17C.1 Carboxylic acids: structure and preparation Quiz: Pearson Edexcel Chemistry, Unit 17
20 questions
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Lesson 17C.1, Carboxylic acids: structure and preparation: 20 multiple choice questions for the Pearson Edexcel Chemistry (9CH0), Unit 17: Organic Chemistry II, written with Revision Ninja.
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The 20 questions
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Which functional group identifies a carboxylic acid?
- -COO-, an ester group bonded to two carbon atoms
- -COOH, a carbonyl group bonded to a hydroxyl group
- -CHO, a carbonyl group bonded to a hydrogen atom
- -CO-, a carbonyl group bonded to two carbon atoms
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Why do carboxylic acids have higher boiling temperatures than alcohols of similar molar mass?
- They have a larger number of carbon atoms per molecule
- They contain more covalent bonds, which are stronger than hydrogen bonds
- They form hydrogen-bonded dimers, which requires more energy to separate
- They are ionic compounds with strong electrostatic forces
-
Which reagent converts a primary alcohol into a carboxylic acid in one step by heating under reflux?
- Concentrated sulfuric acid at room temperature
- Lithium tetrahydridoaluminate in dry ether
- Phosphorus(V) chloride
- Acidified potassium dichromate(VI)
-
What is produced when a nitrile is hydrolysed by heating with dilute acid?
- A carboxylic acid and an ammonium salt
- An alcohol and carbon dioxide, released as the nitrile loses carbon
- A primary amine and water, formed by reduction of the nitrile group
- An ester and water, formed by condensation of the nitrile group
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Which reaction forms a sodium salt from a carboxylic acid?
- Reaction with phosphorus(V) chloride, giving an acyl chloride
- Reaction with lithium tetrahydridoaluminate, giving a primary alcohol
- Reaction with concentrated sulfuric acid, giving an alkene
- Reaction with sodium hydroxide solution, giving the sodium carboxylate and water
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What is the product when a carboxylic acid is reduced by lithium tetrahydridoaluminate?
- A ketone with one fewer carbon atom
- A primary alcohol
- A secondary alcohol with one more carbon atom
- An aldehyde with the same number of carbon atoms
-
Carboxylic acids react with phosphorus(V) chloride. What is the organic product?
- A nitrile
- An acyl chloride
- An alkene
- A primary alcohol
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Which reagents are used to make an ester from a carboxylic acid?
- An alcohol with a concentrated acid catalyst, heated under reflux
- Lithium tetrahydridoaluminate in dry ether
- An alcohol with sodium hydroxide at room temperature
- Phosphorus(V) chloride in cold conditions
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Why is the esterification of a carboxylic acid with an alcohol described as reversible?
- The water formed can hydrolyse the ester back to the acid and alcohol
- The alcohol is consumed completely and cannot be regenerated
- The catalyst is used up during the reaction and must be replaced
- The ester can react with the acid to form a salt and water
-
What is a suitable method for preparing ethanoic acid from ethanol?
- Oxidation with acidified dichromate(VI) under reflux
- Hydrolysis of a nitrile with sodium hydroxide
- Reduction with lithium tetrahydridoaluminate in dry ether
- Heating with sulfuric acid to form ethene
-
Which functional group identifies an ester?
- -CN, a carbon bonded to nitrogen by a triple bond at the end of the chain
- -OH, a hydroxyl group bonded to a carbon atom that is also part of a carbonyl
- -CO-, with a carbonyl group bonded to two carbon atoms in a chain or ring structure
- -COO-, with a carbonyl group bonded to an oxygen that is bonded to a carbon atom
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Why do carboxylic acids have lower solubility in water as the carbon chain length increases?
- The molecules become larger, so they cannot form any hydrogen bonds with the water molecules in solution
- The carboxyl group becomes less polar as the chain gets longer, so the acid no longer dissolves in water
- The acid ionises less in water as the chain gets longer, reducing the number of ions present in solution
- The hydrophobic alkyl part becomes larger, outweighing the hydrogen bonding of the carboxyl group
-
A carboxylic acid is made by hydrolysing a nitrile. Which molecule is the starting material?
- A compound with a -NH2 group, such as ethylamine
- A compound with a -CHO group, such as ethanal
- A compound with a -COCl group, such as ethanoyl chloride
- A compound with a -CN group, such as ethanenitrile
-
What is the product when ethanoic acid reacts with sodium carbonate?
- Ethyl ethanoate and water
- Sodium ethanoate, water and carbon dioxide
- Ethanol and sodium hydrogencarbonate
- Sodium ethanoate and hydrogen gas
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Why is lithium tetrahydridoaluminate needed in dry ether for reducing a carboxylic acid?
- Dry ether is needed to convert the acid into an acyl chloride
- It reacts violently with water, so the reaction must exclude water to work
- It is only soluble in dry ether, which is needed to dissolve the acid
- The reaction needs water to be removed to form an ester
-
Which product forms from the reaction of ethanoic acid with ethanol under acid catalysis?
- Ethyl ethanoate and water
- Ethanal and hydrogen gas
- Ethanol and ethanoate ions
- Ethene and carbon dioxide
-
A student adds sodium hydrogencarbonate to a carboxylic acid and sees gas bubbles. What does this show?
- The acid has reduced the hydrogencarbonate to hydrogen
- The acid is strong enough to release carbon dioxide from hydrogencarbonate
- The acid is a base and has accepted protons from the solution
- The acid has formed a precipitate of sodium carbonate
-
What is the molecular formula of the ester formed from methanoic acid and propan-1-ol?
- C4H10O2
- C4H8O2
- C3H6O2
- C3H8O2
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What is the name of the ester formed from ethanoic acid and ethanol?
- Ethanol ethanoate
- Methyl propanoate
- Ethyl ethanoate
- Ethyl ethanoic acid
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Which reagent oxidises an aldehyde to a carboxylic acid?
- Acidified potassium dichromate(VI) with warming
- Sodium hydroxide solution with heating
- Lithium tetrahydridoaluminate in dry ether
- Phosphorus(V) chloride at room temperature
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