Define a primary alcohol .

A standard hydrogen electrode is the reference half-cell against which all standard electrode potentials are measured. It consists of H 2 gas at 100 kPa bubbled over a platinum electrode in 1 mol dm -3 H + at 298 K, and is assigned a potential of 0.00 V.

True or False? Tertiary alcohols can be oxidised by acidified potassium dichromate(VI).

False. Tertiary alcohols have no hydrogen atom on the carbon bearing the –OH group, so they cannot be oxidised by acidified K 2 Cr 2 O 7 . No colour change is observed.

A secondary alcohol is oxidised to a .......... by acidified potassium dichromate(VI). The orange Cr 2 O 7 2− ions are reduced to .......... Cr 3+ ions.

A secondary alcohol is oxidised to a ketone by acidified potassium dichromate(VI). The orange Cr 2 O 7 2− ions are reduced to green Cr 3+ ions.

How do primary, secondary and tertiary alcohols differ in terms of the carbon attached to the –OH group?

Primary: C bonded to –OH is attached to one other carbon. Secondary: C bonded to –OH is attached to two other carbons. Tertiary: C bonded to –OH is attached to three other carbons.

A primary alcohol can be oxidised first to an .......... and then further oxidised to a .......... acid if excess oxidising agent is used under reflux.

A primary alcohol can be oxidised first to an aldehyde and then further oxidised to a carboxylic acid if excess oxidising agent is used under reflux.

True or False? The colour change from orange to green with acidified K 2 Cr 2 O 7 confirms that an alcohol has been oxidised.

True. When a primary or secondary alcohol is oxidised, the Cr 2 O 7 2− ions are reduced to Cr 3+ , changing the colour from orange to green. Tertiary alcohols give no colour change.

Define a tertiary alcohol .

A fuel cell is an electrochemical cell that converts the chemical energy from a fuel (such as hydrogen) directly into electrical energy, with water as the only product in hydrogen fuel cells.

Define fermentation in alcohol production.

A standard cell potential is the potential difference between two half-cells under standard conditions, calculated as E°(cathode) − E°(anode). A positive value indicates a spontaneous reaction.

C 6 H 12 O 6 .......... 2CO 2 + 2C 2 H 5 OH The arrow is labelled with .......... to show the reaction is catalysed.

C 6 H 12 O 6 → 2CO 2 + 2C 2 H 5 OH The arrow is labelled with enzymes to show the reaction is catalysed.

True or False? Fermentation can produce ethanol at concentrations above 15% because yeast can tolerate high alcohol concentrations.

False. Yeast enzymes are killed once the ethanol concentration reaches approximately 15%, so fermentation stops before higher concentrations are achieved.

What catalyst is used in the production of ethanol from ethene and steam?

Concentrated phosphoric(V) acid (H 3 PO 4 ) or sulfuric acid is used as the catalyst in the electrophilic addition of steam to ethene.

An aldehyde can be reduced to a primary alcohol using .......... as a reducing agent.

An aldehyde can be reduced to a primary alcohol using NaBH 4 (or LiAlH 4 ) as a reducing agent.

True or False? Hydrolysis of an ester with dilute acid produces an alcohol and a carboxylic acid.

True. When an ester is heated with dilute acid or alkali, the ester bond is hydrolysed to regenerate the original alcohol and carboxylic acid.

What is the electrophilic addition route to alcohol production?

An Arrhenius equation is the mathematical relationship between the rate constant k , the activation energy E a , and the temperature T : k = Ae – E a/ RT , where A is the pre-exponential factor and R is the gas constant.

What is Tollens' reagent and what does a positive result look like?

A reducing agent is a species that loses electrons (is oxidised) in a redox reaction, causing another species to be reduced.

To obtain an aldehyde from a primary alcohol, use a .......... amount of acidified K 2 Cr 2 O 7 and .......... the aldehyde off as it forms.

To obtain an aldehyde from a primary alcohol, use a limited amount of acidified K 2 Cr 2 O 7 and distil the aldehyde off as it forms.

True or False? Ketones give a positive result with Tollens' reagent, producing a silver mirror.

False. Ketones cannot be oxidised and give a negative result with Tollens' reagent. Only aldehydes are oxidised, reducing Ag + to silver atoms and forming the silver mirror.

What colour change is observed when acidified potassium manganate(VII) oxidises an alcohol?

The purple MnO 4 - ions are reduced to colourless Mn 2+ ions, so the solution changes from purple to colourless.

Fehling's solution contains .......... ions that oxidise an aldehyde. A positive result gives a .......... precipitate of copper(I) oxide.

Fehling's solution contains Cu 2+ ions that oxidise an aldehyde. A positive result gives a brick red precipitate of copper(I) oxide.

True or False? A secondary alcohol can be oxidised to a carboxylic acid by heating under reflux with excess acidified K 2 Cr 2 O 7 .

False. Secondary alcohols are oxidised only to ketones. They cannot be oxidised further. Only primary alcohols and aldehydes can be oxidised to carboxylic acids.

Describe heating under reflux as a laboratory technique.

A standard electrode potential is the potential of a half-cell measured relative to the standard hydrogen electrode under standard conditions (298 K, 100 kPa, 1 mol dm -3 solutions).

True or False? Acidified potassium dichromate(VI) must be in an acidic medium to act as an oxidising agent.

True. The reduction of Cr 2 O 7 2− requires H + ions supplied by the acid. Without them the dichromate cannot accept electrons and act as an oxidising agent.

Describe complete combustion of alcohols.

A half-equation is an equation showing either the oxidation or the reduction half-reaction separately, with electrons included explicitly to balance the charges.

True or False? Ethanol produced by fermentation is considered a sustainable fuel source.

True. Ethanol produced by fermentation uses crops that absorb CO 2 as they grow, making the cycle approximately carbon neutral and the fuel source renewable.

Blending ethanol with gasoline lowers the .......... density of the fuel, meaning a larger volume is needed for the same distance. Fires are also safer because the flame from pure ethanol is .......... .

Blending ethanol with gasoline lowers the energy density of the fuel, meaning a larger volume is needed for the same distance. Fires are also safer because the flame from pure ethanol is almost invisible .

What socio-economic concern is associated with large-scale ethanol fuel production?

Large quantities of farmland are used to grow fermentation crops, which could otherwise be used for food production. This raises concerns about food security and land use.

The energy density of ethanol is .......... than that of gasoline, so vehicles running on pure ethanol need a .......... fuel tank or more frequent refuelling.

The energy density of ethanol is lower than that of gasoline, so vehicles running on pure ethanol need a larger fuel tank or more frequent refuelling.

True or False? When balancing combustion equations for alcohols, the oxygen atom within the alcohol molecule should be ignored.

False. The oxygen atom already present in the alcohol must be counted when balancing the equation. Ignoring it is a common error that leads to incorrect coefficients.

What is meant by an elimination reaction in organic chemistry?

An endothermic reaction is a reaction in which energy is absorbed from the surroundings, causing the temperature of the surroundings to decrease. The enthalpy change (ΔH) is positive.

Alcohol vapour is passed over a hot catalyst of .......... at around 300 °C to undergo dehydration, or excess hot concentrated .......... or .......... acid can be used instead.

Alcohol vapour is passed over a hot catalyst of aluminium oxide (Al 2 O 3 ) at around 300 °C to undergo dehydration, or excess hot concentrated sulfuric or phosphoric(V) acid can be used instead.

What type of product is formed when an alcohol undergoes an elimination (dehydration) reaction?

An alkene is formed, as water is eliminated and a C=C double bond is produced.

True or False? In the acid-catalysed elimination of an alcohol, the H + from the acid catalyst is consumed in the reaction and is not regenerated.

False. The H + is regenerated: it protonates the –OH group, which leaves as water, and then a neighbouring C–H bond breaks to re-release H + , so the acid acts as a catalyst.

In the elimination mechanism for an alcohol, the water molecule is formed from the .......... group of the alcohol and the .......... from the acid catalyst.

In the elimination mechanism for an alcohol, the water molecule is formed from the –OH group of the alcohol and the H + from the acid catalyst.

Why can alkenes produced by dehydration of alcohols be considered more sustainable than those from crude oil?

Alcohols can be obtained from fermentation of plant material (a renewable source), so the alkene monomers they produce do not depend on crude oil — a finite fossil fuel.

True or False? The common exam error of drawing OH - attacking a hydrogen in the alcohol elimination mechanism is penalised, because this mechanism applies to halogenoalkane elimination, not alcohol dehydration.

True. In acid-catalysed elimination of alcohols, H + protonates the –OH group first; OH - attacking H is the base-induced halogenoalkane elimination mechanism and must not be mixed up.

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Alcohols (AQA A Level Chemistry): Flashcards

Exam code: 7405

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FrontClassifying Alcohols
Define a primary alcohol.

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Cards in this collection (35)

Define a primary alcohol.
A standard hydrogen electrode is the reference half-cell against which all standard electrode potentials are measured. It consists of H₂ gas at 100 kPa bubbled over a platinum electrode in 1 mol dm^-3 H⁺ at 298 K, and is assigned a potential of 0.00 V.
True or False?
Tertiary alcohols can be oxidised by acidified potassium dichromate(VI).
False.
Tertiary alcohols have no hydrogen atom on the carbon bearing the –OH group, so they cannot be oxidised by acidified K₂Cr₂O₇. No colour change is observed.
A secondary alcohol is oxidised to a .......... by acidified potassium dichromate(VI). The orange Cr₂O₇²⁻ ions are reduced to .......... Cr³⁺ ions.
A secondary alcohol is oxidised to a ketone by acidified potassium dichromate(VI). The orange Cr₂O₇²⁻ ions are reduced to green Cr³⁺ ions.
How do primary, secondary and tertiary alcohols differ in terms of the carbon attached to the –OH group?
Primary: C bonded to –OH is attached to one other carbon.
Secondary: C bonded to –OH is attached to two other carbons.
Tertiary: C bonded to –OH is attached to three other carbons.
A primary alcohol can be oxidised first to an .......... and then further oxidised to a .......... acid if excess oxidising agent is used under reflux.
A primary alcohol can be oxidised first to an aldehyde and then further oxidised to a carboxylic acid if excess oxidising agent is used under reflux.
True or False?
The colour change from orange to green with acidified K₂Cr₂O₇ confirms that an alcohol has been oxidised.
True.
When a primary or secondary alcohol is oxidised, the Cr₂O₇²⁻ ions are reduced to Cr³⁺, changing the colour from orange to green. Tertiary alcohols give no colour change.
Define a tertiary alcohol.
A fuel cell is an electrochemical cell that converts the chemical energy from a fuel (such as hydrogen) directly into electrical energy, with water as the only product in hydrogen fuel cells.
Define fermentation in alcohol production.
A standard cell potential is the potential difference between two half-cells under standard conditions, calculated as E°(cathode) − E°(anode). A positive value indicates a spontaneous reaction.
C₆H₁₂O₆ .......... 2CO₂ + 2C₂H₅OH
The arrow is labelled with .......... to show the reaction is catalysed.
C₆H₁₂O₆ → 2CO₂ + 2C₂H₅OH
The arrow is labelled with enzymes to show the reaction is catalysed.
True or False?
Fermentation can produce ethanol at concentrations above 15% because yeast can tolerate high alcohol concentrations.
False.
Yeast enzymes are killed once the ethanol concentration reaches approximately 15%, so fermentation stops before higher concentrations are achieved.
What catalyst is used in the production of ethanol from ethene and steam?
Concentrated phosphoric(V) acid (H₃PO₄) or sulfuric acid is used as the catalyst in the electrophilic addition of steam to ethene.
An aldehyde can be reduced to a primary alcohol using .......... as a reducing agent.
An aldehyde can be reduced to a primary alcohol using NaBH₄ (or LiAlH₄) as a reducing agent.
True or False?
Hydrolysis of an ester with dilute acid produces an alcohol and a carboxylic acid.
True.
When an ester is heated with dilute acid or alkali, the ester bond is hydrolysed to regenerate the original alcohol and carboxylic acid.
What is the electrophilic addition route to alcohol production?
An Arrhenius equation is the mathematical relationship between the rate constant k, the activation energy E_a, and the temperature T: k = Ae^–^E^a/^RT, where A is the pre-exponential factor and R is the gas constant.
What is Tollens' reagent and what does a positive result look like?
A reducing agent is a species that loses electrons (is oxidised) in a redox reaction, causing another species to be reduced.
To obtain an aldehyde from a primary alcohol, use a .......... amount of acidified K₂Cr₂O₇ and .......... the aldehyde off as it forms.
To obtain an aldehyde from a primary alcohol, use a limited amount of acidified K₂Cr₂O₇ and distil the aldehyde off as it forms.
True or False?
Ketones give a positive result with Tollens' reagent, producing a silver mirror.
False.
Ketones cannot be oxidised and give a negative result with Tollens' reagent. Only aldehydes are oxidised, reducing Ag⁺ to silver atoms and forming the silver mirror.
What colour change is observed when acidified potassium manganate(VII) oxidises an alcohol?
The purple MnO₄^- ions are reduced to colourless Mn²⁺ ions, so the solution changes from purple to colourless.
Fehling's solution contains .......... ions that oxidise an aldehyde. A positive result gives a .......... precipitate of copper(I) oxide.
Fehling's solution contains Cu²⁺ ions that oxidise an aldehyde. A positive result gives a brick red precipitate of copper(I) oxide.
True or False?
A secondary alcohol can be oxidised to a carboxylic acid by heating under reflux with excess acidified K₂Cr₂O₇.
False.
Secondary alcohols are oxidised only to ketones. They cannot be oxidised further. Only primary alcohols and aldehydes can be oxidised to carboxylic acids.
Describe heating under reflux as a laboratory technique.
A standard electrode potential is the potential of a half-cell measured relative to the standard hydrogen electrode under standard conditions (298 K, 100 kPa, 1 mol dm^-3 solutions).
True or False?
Acidified potassium dichromate(VI) must be in an acidic medium to act as an oxidising agent.
True.
The reduction of Cr₂O₇²⁻ requires H⁺ ions supplied by the acid. Without them the dichromate cannot accept electrons and act as an oxidising agent.
Describe complete combustion of alcohols.
A half-equation is an equation showing either the oxidation or the reduction half-reaction separately, with electrons included explicitly to balance the charges.
True or False?
Ethanol produced by fermentation is considered a sustainable fuel source.
True.
Ethanol produced by fermentation uses crops that absorb CO₂ as they grow, making the cycle approximately carbon neutral and the fuel source renewable.
Blending ethanol with gasoline lowers the .......... density of the fuel, meaning a larger volume is needed for the same distance. Fires are also safer because the flame from pure ethanol is .......... .
Blending ethanol with gasoline lowers the energy density of the fuel, meaning a larger volume is needed for the same distance. Fires are also safer because the flame from pure ethanol is almost invisible.
What socio-economic concern is associated with large-scale ethanol fuel production?
Large quantities of farmland are used to grow fermentation crops, which could otherwise be used for food production. This raises concerns about food security and land use.
The energy density of ethanol is .......... than that of gasoline, so vehicles running on pure ethanol need a .......... fuel tank or more frequent refuelling.
The energy density of ethanol is lower than that of gasoline, so vehicles running on pure ethanol need a larger fuel tank or more frequent refuelling.
True or False?
When balancing combustion equations for alcohols, the oxygen atom within the alcohol molecule should be ignored.
False.
The oxygen atom already present in the alcohol must be counted when balancing the equation. Ignoring it is a common error that leads to incorrect coefficients.
What is meant by an elimination reaction in organic chemistry?
An endothermic reaction is a reaction in which energy is absorbed from the surroundings, causing the temperature of the surroundings to decrease. The enthalpy change (ΔH) is positive.
Alcohol vapour is passed over a hot catalyst of .......... at around 300 °C to undergo dehydration, or excess hot concentrated .......... or .......... acid can be used instead.
Alcohol vapour is passed over a hot catalyst of aluminium oxide (Al₂O₃) at around 300 °C to undergo dehydration, or excess hot concentrated sulfuric or phosphoric(V) acid can be used instead.
What type of product is formed when an alcohol undergoes an elimination (dehydration) reaction?
An alkene is formed, as water is eliminated and a C=C double bond is produced.
True or False?
In the acid-catalysed elimination of an alcohol, the H⁺ from the acid catalyst is consumed in the reaction and is not regenerated.
False.
The H⁺ is regenerated: it protonates the –OH group, which leaves as water, and then a neighbouring C–H bond breaks to re-release H⁺, so the acid acts as a catalyst.
In the elimination mechanism for an alcohol, the water molecule is formed from the .......... group of the alcohol and the .......... from the acid catalyst.
In the elimination mechanism for an alcohol, the water molecule is formed from the –OH group of the alcohol and the H⁺ from the acid catalyst.
Why can alkenes produced by dehydration of alcohols be considered more sustainable than those from crude oil?
Alcohols can be obtained from fermentation of plant material (a renewable source), so the alkene monomers they produce do not depend on crude oil — a finite fossil fuel.
True or False?
The common exam error of drawing OH^- attacking a hydrogen in the alcohol elimination mechanism is penalised, because this mechanism applies to halogenoalkane elimination, not alcohol dehydration.
True.
In acid-catalysed elimination of alcohols, H⁺ protonates the –OH group first; OH^- attacking H is the base-induced halogenoalkane elimination mechanism and must not be mixed up.

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