Carboxylic acids

A student heats a known volume of water by burning propanol.

The student investigates the mass of propanol needed to increase the temperature of the water by 50 °C.

Figure 9 shows the apparatus the student uses.

The student carries out the investigation using the following six steps.

The steps are not shown in the correct order.

step P find the final mass of the spirit burner containing propanol

step Q measure the initial temperature of the water

step R put 100 cm³ water into the beaker

step S find the initial mass of the spirit burner containing propanol

step T when the temperature of the water has increased by 50 °C extinguish the flame

step U place the spirit burner under the beaker of water and light the spirit burner

Write the steps in the correct order.

The first two steps have been completed for you.

State what should be used to find the mass of the spirit burner.

The student finds that 1.40 g of propanol is needed to increase the temperature of the water by 50 °C.

Calculate the mass of propanol needed to increase the temperature of the water by 1 °C.

Alcohols can be oxidised to produce carboxylic acids.

Propanol can be oxidised to propanoic acid.

Complete Figure 10 by giving the names of the missing compounds.

*(c) Compound J is a carboxylic acid and compound K is an alcohol.

Figure 11 gives some information about compounds J and K.

Describe, using Figure 11 and your own knowledge, the similarities and differences between compounds J and K.

Include information about

• the atoms in each molecule

• the structure and bonding

• the properties of each substance.

Crisp packets are often made from poly(propene) coated with a thin layer of aluminium on the inside.

Poly(propene) is a polymer made from the monomer propene, CH₂CHCH₃.

What is the relative formula mass of propene?

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

Describe how monomer molecules combine to make polymers.

Crisps go stale when exposed to the atmosphere.

In an experiment some crisp packets were made from aluminium, some from poly(propene) and some from poly(propene) coated with aluminium. These packets were tested.

Figure 15 shows the results.

Low porosity is an advantage of using poly(propene) coated with aluminium as it prevents the crisps from becoming damp.

Explain, using Figure 15, one other advantage of using poly(propene) coated with aluminium.

The aluminium coating can be replaced by a very thin layer of material called a nanosheet.

The nanosheet is made from amino acids and is less than 100 nm thick.

Explain why the nanosheet layer would be better than aluminium as a coating for crisp packets.

Nanosheet layers can be made from amino acids.

An equation showing a reaction of an amino acid, C₂H₅NO₂, is

Calculate the mass of water formed when 105 g of this amino acid reacts.

(relative formula masses: C₂H₅NO₂ = 75, H₂O = 18)

Some crisps contain malic acid.

The structure of one molecule of malic acid is shown in Figure 16.

Malic acid has two types of functional group.

One type is the –COOH functional group.

Give the name of this functional group.

Name the other functional group.

Crisp packets are often made from poly(propene) coated with a thin layer of aluminium on the inside.

Poly(propene) is a polymer made from the monomer propene, CH₂CHCH₃.

What is the relative formula mass of propene?

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

Describe how monomer molecules combine to make polymers.

Crisps go stale when exposed to the atmosphere.

In an experiment some crisp packets were made from aluminium, some from poly(propene) and some from poly(propene) coated with aluminium. These packets were tested.

Figure 5 shows the results.

Low porosity is an advantage of using poly(propene) coated with aluminium as it prevents the crisps from becoming damp.

Explain, using Figure 5, one other advantage of using poly(propene) coated with aluminium.

The aluminium coating can be replaced by a very thin layer of material called a nanosheet.

The nanosheet is made from amino acids and is less than 100 nm thick.

Explain why the nanosheet layer would be better than aluminium as a coating for crisp packets.

Nanosheet layers can be made from amino acids.

An equation showing a reaction of an amino acid, C₂H₅NO₂, is

Calculate the mass of water formed when 105 g of this amino acid reacts.

(relative formula masses: C₂H₅NO₂ = 75, H₂O = 18)

Some crisps contain malic acid.

The structure of one molecule of malic acid is shown in Figure 6.

Malic acid has two types of functional group.

One type is the –COOH functional group.

Give the name of this functional group.

Name the other functional group.

Figure 12 shows the structure of the molecules of three organic compounds.

Each molecule in Figure 12 contains a different functional group.

Circle the alkene functional group in propene.

Propene reacts with bromine water.

Complete the equation for the reaction of propene with bromine by drawing the structure of a molecule of the product.

H H

H H

propene bromine product

Propanoic acid reacts with calcium carbonate, CaCO₃, to form calcium propanoate, Ca(C₂H₅COO)₂, and two other products.

Name the two other products.

*(b) Glucose, C₆H₁₂O₆, is a carbohydrate.

A dilute solution of ethanol can be produced from glucose by fermentation.

The dilute solution of ethanol can then be processed to form a concentrated solution of ethanol.

Describe how the fermentation of glucose is carried out and how the dilute solution of ethanol produced can then be processed to form a concentrated solution of ethanol.

You may include diagrams in your answer.

Figure 14 shows the structure of a molecule of hydrocarbon Z, C₄H₈.

Give the name of hydrocarbon Z shown in Figure 14.

Complete the balanced equation for the reaction of hydrocarbon Z, C₄H₈, with bromine.

Draw the repeating unit of the addition polymer formed when hydrocarbon Z undergoes polymerisation.

Figure 15 shows the arrangement of atoms in a molecule of an alcohol.

Give the name of the carbon‑containing product formed when the alcohol in Figure 15 undergoes dehydration.

Give the formula of the functional group of the product formed when the alcohol in Figure 15 undergoes oxidation.

A student wants to investigate the amount of energy released when 1.00 g of the alcohol is burned.

They set up the apparatus shown in Figure 16 to measure the temperature rise of the water.

State why this apparatus is not suitable for use in this experiment.

Some alcohols can react with some carboxylic acids to form polyesters, which are condensation polymers.

Figure 17 shows the repeating unit of the polyester molecule formed in a reaction between a carboxylic acid and an alcohol.

Give the formula of the other product formed in this reaction.

Draw the structure of one molecule of the alcohol used to produce the polyester shown in Figure 17, showing all covalent bonds.

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

Figure 14

What happens to propanol when it forms compound Y ?

Compound Y can also be formed in the following reaction

C H C H

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

Compound Z is a carboxylic acid.

Which of the following shows the functional group of a carboxylic acid?

Compound Z is an acid and turns litmus and universal indicator papers red. Compound Z also shows other acidic properties.

Devise an experiment that would show another acidic property of compound Z.

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

sucrose

Calculate the minimum mass of sucrose needed to produce 26.9 g of ethanol.

(relative formula masses: C₂H₅OH = 46, C₁₂H₂₂O₁₁ = 342)

minimum mass of sucrose =_........

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

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

number of atoms =_........

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.

Pentanol is the next member of this series. A molecule of pentanol contains five carbon atoms.

Suggest the formula of a molecule of pentanol.

Draw the structure of a molecule of ethanol. Show all bonds.

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.

Complete the equation for this reaction.

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, CH3₃COOH = 60)

*(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.

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

Figure 3 shows the structure of two monomers.

Monomer B contains a carboxylic acid group.

Describe what you would see when a small amount of solid sodium carbonate is added to a solution of monomer B.

When monomer A and monomer B react together they polymerise to form a polymer and one other product.

Name the type of polymerisation that takes place and name the other product.

type of polymerisation_........

name of other product_........

A naturally occurring polymer is made by combining monomers called nucleotides.

Give the name of this natural polymer.

Some polymerisation reactions produce ammonia as a waste product.

A student is given a sample of pure, dry ammonia gas.

The student suggests the following method to test for ammonia gas.

step 1 take some dry, blue litmus paper step 2 place the dry litmus paper into the dry gas step 3 observe any change in colour of the litmus paper

This test for ammonia will not work.

Give two changes that should be made to this test for it to work.

Alcohols can be dehydrated.

Complete the balanced equation for the dehydration of butan‑1‑ol by drawing the structures of the two products in the boxes. Name the two products.

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

The reaction is carried out at 30C.

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

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

In this reaction ethanol is

Draw the structure of a molecule of ethanoic acid, CH₃COOH, showing all covalent bonds.

The apparatus in Figure 16 can be used to investigate the temperature rise produced in a known mass of water when a sample of ethanol is burned.

The first steps of the method are

NK =$put=NMMcm³ 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

Describe the remaining steps of the method that are needed to determine the mass of ethanol required to raise the temperature of the water by 30C.

In a different experiment, separate samples of the alcohols methanol, ethanol, propanol, butanol and pentanol were burned to determine the mass of each alcohol that needs to be burned to raise the temperature of 100 cm³ water by 10C.

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

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

The reaction is carried out at 30C.

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

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

In this reaction ethanol is

Draw the structure of a molecule of ethanoic acid, CH₃COOH, showing all covalent bonds.

The apparatus in Figure 3 can be used to investigate the temperature rise produced in a known mass of water when a sample of ethanol is burned.

The first steps of the method are

NK $put NMMcm³ 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

Describe the remaining steps of the method that are needed to determine the mass of ethanol required to raise the temperature of the water by 30C.

In a different experiment, separate samples of the alcohols methanol, ethanol, propanol, butanol and pentanol were burned to determine the mass of each alcohol that needs to be burned to raise the temperature of 100 cm³ water by 10C.

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

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.

The theoretical temperature rise for burning a given mass of ethanol is 82.4 °C.

In the experiment the actual temperature rise for burning this mass of ethanol was only 34.8 °C. One reason why the temperature rise is less than expected is that the ethanol does not burn completely.

Give a reason why, even if the ethanol burns completely, the actual temperature rise is much less than the theoretical value.

Explain how the method described above could be improved to give a temperature rise closer to the theoretical value.

The amount of heat energy used to raise the temperature of the water by 34.8 °C can be calculated using

heat energy = 210 × temperature rise

Calculate the amount of heat energy used.

heat energy =_........ (energy units)

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

H H H
H H H H

H H H
H H H H

propanol butanol

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.

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.

Write the word equation for the reaction when propanol oxidises when it is exposed to air.

What is the formula of the functional group in carboxylic acids?

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 3.

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.

The theoretical temperature rise for burning a given mass of ethanol is 82.4 °C.

In the experiment the actual temperature rise for burning this mass of ethanol was only 34.8 °C. One reason why the temperature rise is less than expected is that the ethanol does not burn completely.

Give a reason why, even if the ethanol burns completely, the actual temperature rise is much less than the theoretical value.

Explain how the method described above could be improved to give a temperature rise closer to the theoretical value.

The amount of heat energy used to raise the temperature of the water by 34.8 °C can be calculated using

heat energy = 210 × temperature rise

Calculate the amount of heat energy used.

heat energy =_........ (energy units)

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.

Write the word equation for the reaction when propanol oxidises when it is exposed to air.

What is the formula of the functional group in carboxylic acids?