Alcohols & Carboxylic Acids (Edexcel GCSE Chemistry)

Alcohols and carboxylic acids are important organic compounds.

Figure 8 shows the names and formulae of three alcohols in a homologous series.

Figure 8   

Predict the formula of the alcohol that has five carbon atoms in its molecule, using the information in Figure 8.

Calculate the relative formula mass of ethanol, C₂H₅OH.

(relative atomic masses: H = 1, C = 12, O = 16)

relative formula mass = ..............................................................

Ethanol can be oxidised to form ethanoic acid.

Draw the structure of a molecule of ethanoic acid, showing all the covalent bonds.

The temperature rise in water when liquid fuels burn can be found using the equipment shown in Figure 9.

Figure 9

(2)

Figure 10

(2)

What is the reading on the following thermometer?

Ethanol can be used as a liquid fuel.

A student investigates how much heat energy is released when a known mass of ethanol is burned.

The apparatus is set up as shown in Figure 15.

A known volume of water is placed in a metal can.
The temperature of the water is measured.
The ethanol is ignited and placed under the beaker so that the flame is touching the beaker.
The water is heated by the flame.
The flame is extinguished.
The final temperature of the water is measured.

Figure 15

Propanol and butanol are both members of the same homologous series as ethanol.

Propanol and butanol can also be burned in the apparatus shown in Figure 15.

Give three reasons why ethanol, propanol and butanol are members of the same homologous series.

reason 1 ..............................................

reason 2 ..............................................

reason 3 .............................................

Ethanol can oxidise when exposed to air to produce ethanoic acid and water.
Propanol can also oxidise in a similar reaction when it is exposed to air.

Ethanol is produced by fermentation.

Which of the following conditions is not required to produce ethanol by fermentation?

Ethanol is made by fermentation of a carbohydrate dissolved in water, in the presence of yeast.

The reaction is carried out at 30 °C.

Explain why the reaction is carried out at a temperature of 30 °C rather than at a temperature of 80 °C.

Ethanol, C₂H₅OH, can be converted into ethanoic acid, CH₃COOH.

1. put 100cm³ of water into a beaker
2. determine the mass of the burner containing ethanol
3. measure the initial temperature of the water
4. place the burner under the beaker of water
5. light the wick

(3)

Draw a graph of the mass of each alcohol required to raise the temperature of 100 cm³ of water by 10°C against the number of carbon atoms in one molecule of that alcohol.

(3)

What are the names of compounds A and B?

Ethanol can be produced by the fermentation of glucose solution.

Which of these shows the word equation for the fermentation of glucose solution?

The names and formulae of the first four alcohols in the homologous series of alcohols are given in Figure 12.

Figure 12

Ethanol is present in alcoholic drinks, such as wine.

When a bottle of wine is left open some of the ethanol reacts with the oxygen in the air to form ethanoic acid, CH₃COOH, and water.

(2)

CH₃CH₂OH + .......................... → CH₃COOH + ........................

ii)

Which calculation shows the percentage by mass of hydrogen in ethanoic acid?

(relative atomic mass of hydrogen, H = 1,

relative formula mass of ethanoic acid, CH₃COOH = 60)

(1)

	☐	A
	☐	B
	☐	C
	☐	D

Polymers have many uses.
However, the disposal of polymers after use can be a problem.
The uses of polymers are related to their properties.
Some uses of three common polymers are given in Figure 13.

Figure 13

Discuss the reasons for using these polymers in the ways shown in Figure 13 and the problems in disposing of these polymers.

Fermentation of carbohydrates produces a dilute solution of ethanol.

This need further processing by fractional distillation to produce a concentrated solution of ethanol.

Some of the steps of fractional distillation are shown below.

The steps shown are not in the correct order.

Which of the following shows the correct order of the steps above?

This question is about alcohols.

(2)

Figure 14

(1)

A student used an alcohol burner to find the mass of different alcohols needed to raise the temperature of 100 cm³ of water by 20 °C.

Figure 15 shows their results.

Figure 15

(6)

Which of the following statements about butanol is not correct?

Figure 10 shows a flask fitted with a cotton wool plug.
The flask contains an aqueous solution of a carbohydrate.

Figure 10

Figure 11

This apparatus did not produce a very concentrated solution of ethanol.
Describe how the apparatus can be altered to produce a more concentrated solution of ethanol.

(2)

The equation for the fermentation of a carbohydrate is

C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂

Calculate the maximum mass of carbon dioxide that could be produced if 135 g of this carbohydrate is fully fermented

(relative formula masses: CO₂= 44; C₆H₁₂O₆= 180)

mass of carbon dioxide = ............................... g

Figure 12 shows information about some compounds in the same homologous series.

Figure 12

Explain, using the data in Figure 12, why these compounds belong together in the same homologous series.

Propanol, C₃H₇OH, can undergo reactions to form compounds Y and Z shown in Figure 14.

Figure 14

(1)

Explain how bromine water can be used to distinguish between compound X and compound Y.

(3)

	☐	A
	☐	B
	☐	C
	☐	D

Higher Only

The balanced equation for the production of ethanol from the carbohydrate sucrose is

+ 

Calculate the minimum mass of sucrose needed to produce 26.9 g of ethanol.
(relative formula masses: )

minimum mass of sucrose = ................................. g

Higher Only

Calculate the total number of atoms in 10.0 g of sucrose, C₁₂H₂₂O₁₁.

(relative formula mass: C₁₂H₂₂O₁₁ = 342; Avogadro constant = 6.02 × 10²³)

Propanoic acid is a carboxylic acid. Its formula is CH₃–CH₂–COOH.

Carboxylic acids can be made by the oxidation of alcohols.

Complete the following equations for some of the reactions of propanoic acid.

A piece of magnesium was added to 100 cm³ of an aqueous acid. The time taken for the metal to react completely was measured. 

This experiment was repeated using different aqueous acids. The same volume of acid was used in each experiment and the pieces of magnesium used were identical. 

In one experiment the reaction was carried out at a different temperature.

Explain the following in terms of collision rate between reacting particles.

(2)

(2)

(3)

Ethanol, C₂H₅OH, can be produced by the fermentation of glucose, C₆H₁₂O₆

C₆H₁₂O₆  → 2C₂H₅OH + 2 ........................................

Higher Only

Ethanol can also be produced by the reaction between ethene and steam.
The equation for the reaction is

C₂H₄ (g) + H₂O (g)  C₂H₅OH (g)

This question is about carboxylic acids.

The table below shows information about three carboxylic acids.

Complete the table. 

Higher Only

Solutions of ethanoic acid and hydrochloric acid have different pH levels at the same concentration.

Explain the difference in pH levels between the two acids 

A student adds sodium to a solution of ethanoic acid in an open flask on a balance.

Explain what happens to the mass of the flask and its contents during the reaction.

In a separate reaction, a student adds ethanoic acid to zinc carbonate.

Describe and give the result of a test the student would do to identify the gas produced.