Properties of hydrocarbons

Crude oil is a mixture of hydrocarbons.

The majority of hydrocarbons in crude oil belong to one homologous series.

Give the name of this series.

When hydrocarbons undergo combustion, water is produced.

Draw a dot and cross diagram of a molecule of water.

One compound in crude oil contains 0.96 g of carbon atoms combined with 0.32 g of hydrogen atoms.

Calculate the empirical formula of this compound.

(relative atomic masses: C = 12, H = 1.0)

*(d) Crude oil is separated into useful products called fractions using fractional distillation.

Figure 14 shows a fractional distillation column and the fractions kerosene and fuel oil.

Kerosene and fuel oil have different uses depending on their properties.

Describe the properties and uses of kerosene and fuel oil. Include in your answer

• the difference in boiling point

• the difference in viscosity

• the difference in ease of ignition

• their uses and how fuel oil can be converted into kerosene.

Crude oil is a mixture of hydrocarbons.

The majority of hydrocarbons in crude oil belong to one homologous series.

Give the name of this series.

When hydrocarbons undergo combustion, water is produced.

Draw a dot and cross diagram of a molecule of water.

One compound in crude oil contains 0.96 g of carbon atoms combined with 0.32 g of hydrogen atoms.

Calculate the empirical formula of this compound.

(relative atomic masses: C = 12, H = 1.0)

Figure 9 shows the structure of one molecule of three different compounds, X, Y and Z.

The molecules of the compounds shown in Figure 9 all contain the same number of carbon atoms.

Give the number of carbon atoms in a molecule of compound X.

Compound X contains carbon and one other element.

Give the name of the other element in compound X.

Which of the compounds in Figure 9 is a hydrocarbon?

Which of the compounds in Figure 9 have the same molecular formula?

Figure 10 shows where fractions are produced in the fractional distillation of crude oil.

Complete the sentences about fractions obtained from crude oil.

The fraction with the smallest molecules is called_........ .

Compared to petrol, the boiling point of kerosene is_........ .

When petrol burns, one product is_........ .

When some impure hydrocarbon fuels are burned, sulfur dioxide is one of the products.

Some sulfur dioxide gas is dissolved in water to form solution W.

When solution W is added to sodium hydroxide solution of pH 12

• the pH changes

• the temperature increases.

Explain how the pH changes and why the temperature increases.

Most hydrocarbons found in fossil fuels are members of the alkane homologous series.

State two features of an homologous series.

Which molecule is in the same homologous series as CH₄?

A fossil fuel contains carbon and sulfur.

Explain how the products of the complete combustion of this fossil fuel would affect the environment.

Incomplete combustion of fuels may produce carbon monoxide.

Write the balanced equation for the incomplete combustion of heptane, C₇H₁₆, where all of the carbon atoms form carbon monoxide.

Damp iron wool reacts with oxygen in the air. A student uses the apparatus in Figure 7 to investigate the percentage of oxygen in the atmosphere.

The initial volume of air in the measuring cylinder was 18.0 cm³.

The student left the apparatus overnight.

The volume of gas in the measuring cylinder the next day was 14.5 cm³.

To the nearest whole number, what percentage of the air has reacted with the iron wool?

Describe one improvement the student could make to this method to ensure that all of the oxygen in the measuring cylinder has reacted.

When hydrocarbon fuels are burned, the products are water and carbon dioxide.

Describe what needs to be done to the apparatus in Figure 8 to collect the water and show that carbon dioxide has been produced.

A hydrocarbon, C_xH_y, is burned in excess oxygen, forming 26.4 g of carbon dioxide and 5.4 g of water.

The relative formula mass of C_xH_y is 78.

Calculate the molecular formula of the hydrocarbon C_xH_y.

(relative atomic masses: H = 1.0, C = 12; relative formula masses: H₂O = 18, CO₂ = 44)

molecular formula =_........

Crude oil is a mixture of hydrocarbons.

Crude oil can be separated into useful fractions by the process of fractional distillation in a fractionating column.

Figure 15 shows a fractionating column, the fractions obtained and the trend in viscosity of the fractions.

Which row shows the correct uses for bitumen, diesel oil and fuel oil?

Explain the trend in the viscosity of the fractions.

Hydrocarbon X was cracked to form one molecule of hexane, C₆H₁₄, and one molecule of alkene Y.

The relative formula mass of Y is 56. The empirical formula of Y is CH₂.

Deduce the molecular formula of hydrocarbon X.

Show your working.

(relative atomic masses: H = 1.0, C = 12)

*(c) Large quantities of methane are used as a fuel.

Figure 16 shows a Bunsen burner.

Methane can be used as fuel for the Bunsen burner.

The air-hole on the chimney of the Bunsen burner can be opened and closed.

Explain the effect of opening and closing the air-hole of the Bunsen burner on the products of combustion of methane and the harm that using large quantities of methane as a fuel can cause.

The structure of one molecule of a compound is shown in Figure 10.

What is the molecular formula of the compound in Figure 10?

The compound in Figure 10 is an unsaturated hydrocarbon.

State why the compound is described as an unsaturated hydrocarbon.

Many molecules of the compound in Figure 10 combine to form substance Y. Figure 11 shows part of a molecule of substance Y.

H H H H H H H H

Figure 11

What type of substance is Y?

One molecule of the compound in Figure 10 has a mass of 6.9810^–23g.

64 800 of these molecules combine to form one molecule of Y.

Calculate the mass of this molecule of Y in g.

*(d) Alkanes can be burned in air. Different products can be formed as the combustion of alkanes can be complete or incomplete.

An investigation was carried out to compare the energy released when the first four alkanes in the homologous series were burned. Equal amounts of these alkanes were burned to heat 100 cm³ of water. The temperature change for each alkane is shown in Figure 12.

Discuss the complete and incomplete combustion of these alkanes and the trend in the energy changes they produced.

You should give word equations in your answer.

Figure 8 shows some information about the composition of pollutant exhaust gases from the engines of two different vehicles.

Give two ways in which the data in Figure 8 shows that the diesel engine is more damaging to the environment than the petrol engine.

Explain, using information from Figure 8, one way in which the diesel engine is less damaging to the environment than the petrol engine.

Which statement about the members of the alkane homologous series is correct?

Which one of the following hydrocarbons belongs to the same homologous series as octane, C₈H₁₈?

Write the balanced equation for the complete combustion of octane, C₈H₁₈.

Pentadecane, C₁₅H₃₂, is a hydrocarbon and is used as a fuel.

The incomplete combustion of pentadecane produces carbon monoxide. Carbon monoxide is a toxic gas.

Explain why the incomplete combustion of pentadecane can produce carbon monoxide as one of the products.

Explain how carbon monoxide behaves as a toxic gas.

1 mole of pentadecane can be cracked to form 1 mole of octane, C₈H₁₈, and 1 mole of propene, C₃H₆, and 2 moles of another product.

Complete the balanced equation for this reaction by adding the formula of the missing product.

Figure 11 shows the reaction of propene, C₃H₆, with water.

H H H

Figure 11

Figure 12 shows some bond energies.

Use the bond energies in Figure 12 to calculate the energy change of the reaction in Figure 11.

energy change of reaction =_........ kJ

Methane gas, CH₄, was burned using the apparatus shown in Figure 13.

Explain why water droplets form on the bottom of the beaker of cold water.

Methane is a hydrocarbon fuel.

Complete the word equation for the complete combustion of methane in oxygen.

methane +_........ water +_........

The incomplete combustion of methane can produce carbon and carbon monoxide.

Give the reason why carbon and carbon monoxide are produced in the incomplete combustion of methane.

Crude oil is a complex mixture of hydrocarbons. Crude oil can be separated into useful fractions by fractional distillation.

Figure 10 shows a fractional distillation column and the fractions produced when crude oil is distilled.

Name the fraction in Figure 10 that is used to surface roads.

Name the fraction in Figure 10 that contains hydrocarbons with the lowest boiling point.

When crude oil is fractionally distilled, the demand for some fractions is more than the amount produced.

Figure 11 shows the relative amounts of each fraction in a crude oil and the relative demand for each of these fractions.

Which of the following shows the fractions where the relative demand is greater than the relative amount in the crude oil?

Cracking involves the breaking down of large hydrocarbon molecules into smaller hydrocarbon molecules.

Octane, C₈H₁₈, can be cracked to produce one molecule of ethene, C₂H₄, and one molecule of C_xH₁₄.

Determine the value of x in the molecule of C_xH₁₄.

Dodecane is a large hydrocarbon molecule. When one molecule of dodecane is cracked the products are one molecule of octane and one molecule of butene.

dodecane octane + butene

Calculate the maximum mass of octane that could be produced when 340 g of dodecane is cracked in this reaction.

(relative formula masses: dodecane = 170, octane = 114)

Propene can be produced by the cracking of some hydrocarbons obtained from crude oil.

The equation shows the cracking of one molecule of decane to produce one molecule of butene and one molecule of another product.

decane butene

Calculate the values of x and y in C_xH_y.

State the total mass of products formed if 25 g of decane is cracked in this way.

The structure of a molecule of ethene is shown in Figure 8.

Figure 9 shows the incomplete dot and cross diagram for a molecule of ethene.

Complete Figure 9 to show the electrons of the C C double bond.

The incomplete combustion of ethene in air produces water as one of the products.

Give the name of another product of the incomplete combustion of ethene.

Substance X is an unsaturated hydrocarbon. The structure of a molecule of substance X is shown in Figure 10.

Explain how the structure of substance X shows that it is an unsaturated hydrocarbon.

Two liquid hydrocarbons, A and B, were tested with bromine water. One hydrocarbon was known to be an alkane. The other hydrocarbon was known to be an alkene.

Each hydrocarbon was shaken with a few drops of bromine water.

The results of the tests were hydrocarbon A + bromine water: the mixture turned from orange to colourless. hydrocarbon B + bromine water: the orange colour remained.

Explain these results.

Most of the fuels used today are obtained from crude oil.

Which statement about crude oil is correct?

Crude oil is separated into several fractions by fractional distillation. Two of these fractions are kerosene and diesel oil.

State a use for each of these fractions.

Figure 13 shows where the fractions kerosene and diesel oil are produced in the fractionating column.

Kerosene is obtained higher up the column than diesel oil. Kerosene and diesel oil fractions have slightly different properties.

Choose a property. State how this property for kerosene compares with the property for diesel oil.

Figure 14 shows the formulae of a molecule of butane and of a molecule of pentane. Butane and pentane are neighbouring members of the same homologous series.

H H H H
H H H H H

H H H H
H H H H H

butane pentane

Figure 14

Explain, using these formulae, why butane and pentane are neighbouring members of the same homologous series.

Butane has the formula C₄H₁₀.

Calculate the mass of carbon in 100 g of butane.

Give your answer to three significant figures.

(relative atomic masses: H = 1.00, C = 12.0; relative formula mass: C₄H₁₀ = 58.0)

You must show your working.

Butane burns completely in air to form carbon dioxide and water.

Write the word equation for this reaction.

Most of the fuels used today are obtained from crude oil.

Which statement about crude oil is correct?

Crude oil is separated into several fractions by fractional distillation. Two of these fractions are kerosene and diesel oil.

State a use for each of these fractions.

Figure 1 shows where the fractions kerosene and diesel oil are produced in the fractionating column.

Kerosene is obtained higher up the column than diesel oil. Kerosene and diesel oil fractions have slightly different properties.

Choose a property. State how this property for kerosene compares with the property for diesel oil.

Figure 2 shows the formulae of a molecule of butane and of a molecule of pentane. Butane and pentane are neighbouring members of the same homologous series.

H H H H
H H H H H

butane pentane

Figure 2

Explain, using these formulae, why butane and pentane are neighbouring members of the same homologous series.

Butane has the formula C₄H₁₀.

Calculate the mass of carbon in 100 g of butane.

Give your answer to three significant figures.

(relative atomic masses: H = 1.00, C = 12.0; relative formula mass: C₄H₁₀ = 58.0)

You must show your working.

Ethene, C₂H₄, is an unsaturated hydrocarbon.

Explain why ethene is an unsaturated hydrocarbon.

A sample of ethene is burned completely in oxygen.

Write the balanced equation for this reaction.

Ethene can be polymerised to form poly(ethene).

Describe what you would see when a sample of ethene and a sample of poly(ethene) are shaken with separate, small volumes of bromine water.

A different hydrocarbon has a relative formula mass of 84. It has an empirical formula of CH₂.

Deduce the molecular formula of this hydrocarbon.

You must show your working.

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

Crude oil is found in the Earth’s crust.

Which of the statements about crude oil is correct?

The substances ethane, C₂H₆, octane, C₈H₁₈, and pentadecane, C₁₅H₃₂, are all found in crude oil.

These substances

Use a word from the box to complete each of the sentences about the fractional distillation of crude oil.

Each word may be used once, more than once, or not at all.

The separation of crude oil into fractions occurs in a fractional distillation column.

Before crude oil is passed into the column it is_........ .

During the distillation, vapour rises up the column until it is cold enough for the

vapour to form a liquid. The vapour has been_........ .

Complete this sentence by underlining the correct answer in the box.

Compared with the fraction from the top of the column,

has more carbon atoms per molecule.

the fraction from the bottom of the column has a lower viscosity.

is easier to ignite.

When crude oil is separated into fractions, the amount of each fraction obtained rarely matches the demand for that fraction.

Figure 7 shows the relative amounts of four of the fractions obtained from a crude oil and the relative demand for each of these fractions.

State the fraction for which the relative amount obtained exceeds the relative demand.

In January 2015 the United Kingdom produced 850 000 barrels of crude oil per day. 45% of this crude oil was fuel oil.

Calculate the number of barrels of fuel oil present in the 850 000 barrels of crude oil.

Give your answer to two significant figures.

Crude oil is a complex mixture of substances.

Crude oil can be separated into useful fractions by fractional distillation.

Figure 7 shows a fractional distillation column and the fractions produced when a sample of crude oil is distilled.

The properties of these fractions vary from the top of the column to the bottom of the column.

Which of the following is a trend in a property of the fractions obtained from the top of the column to those obtained from the bottom?

Most of the substances in crude oil are alkanes.

Explain why alkanes are described as hydrocarbons.

Figure 8 shows a graph of the boiling points of some alkanes against the number of carbon atoms in one molecule of each alkane.

Explain the pattern shown by this graph.

Use the information in Figure 9 to give the name of the fraction that is most likely to need to be cracked.

_........

In a cracking reaction, reactants are heated to form products. This reaction is endothermic.

On the axes provided, draw the reaction profile of this reaction. Label the energy of the reactants, the energy of the products and the activation energy of the reaction.

Dodecane, C₁₂H₂₆, can be cracked to form useful products.

Complete the equation for the cracking of dodecane by filling in the formula of the single molecule needed to balance the equation.