Atmospheric pollutants

This question is about carbon and some carbon compounds.

Two forms of pure carbon are graphite and Buckminsterfullerene.

Explain why graphite is used as a lubricant.

Calculate the mass, in kg, of five moles of Buckminsterfullerene, C₆₀.

(relative atomic mass: C = 12)

A molecule in an homologous series has the formula C₉H₂₁N.

What is the formula of the next molecule in this homologous series?

A Bunsen burner burns methane gas, CH₄.

A student investigates the time taken to heat up a beaker of water using this Bunsen burner.

Figure 9 shows the apparatus used.

The student sees that a large amount of carbon forms as a black solid on the underside of the gauze.

The teacher said that the investigation would be improved if no carbon forms.

Explain what the student should do to stop carbon forming on the underside of the gauze.

*(d) Natural processes and human activities change the amount of carbon dioxide in the atmosphere.

Figure 10 shows the concentration of carbon dioxide in the atmosphere measured in one location and the mean global temperature from 1960 to 2000.

Evaluate whether the data in Figure 10 shows that the change in the amount of carbon dioxide is leading to climate change.

Your answer should include

• the natural processes that change the amount of carbon dioxide in the atmosphere

• the human activities that change the amount of carbon dioxide in the atmosphere

• how carbon dioxide contributes to the greenhouse effect and climate change.

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.

Figure 9 shows the percentage of three gases, X, Y and Z, in the Earth’s early atmosphere.

What is the name of gas Z ?

It is thought that small quantities of hydrogen sulfide, H₂S, were also in the Earth’s early atmosphere.

Draw the dot and cross diagram for a molecule of hydrogen sulfide.

Show outer electrons only.

Acid rain is caused by some pollutant gases present in the atmosphere.

Explain how impurities in fossil fuels can result in acid rain.

A student investigates the effect of acid rain on cress plants.

The student uses this method.

step 1 grow 20 cress plants in each of two dishes, A and B

step 2 water the cress plants in dish A with 10 cm³ of dilute hydrochloric acid with a pH of 2

step 3water the cress plants in dish B with 10 cm³ of pure water with a pH of 7

step 4 repeat steps 2 and 3 every day for one week

step 5 count how many plants are still alive after one week.

State what piece of equipment the student could use to measure the pH of each liquid.

Explain one improvement that the student could make to the method to make the results more valid.

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.

Diesel oil is a mixture of hydrocarbons that can be obtained from crude oil.

State the name of the process used to separate diesel oil from crude oil.

Diesel oil contains alkanes. These alkanes are part of an homologous series.

Which statement about compounds in this homologous series is true?

When fuels such as diesel oil are burned, the high temperatures produced can cause nitrogen and oxygen in the air to form the pollutant nitrogen dioxide.

Complete the balanced equation for the reaction.

Explain how the greenhouse effect is caused by the gases produced by the complete combustion of diesel oil.

*(e) Diesel oil can contain impurities of sulfur. Burning diesel oil containing impurities of sulfur can result in acid rain. Acid rain is harmful to the environment.

Explain how acid rain is formed and the harm it can do.

Diesel oil is a mixture of hydrocarbons that can be obtained from crude oil.

State the name of the process used to separate diesel oil from crude oil.

Diesel oil contains alkanes. These alkanes are part of an homologous series.

Which statement about compounds in this homologous series is true?

When fuels such as diesel oil are burned, the high temperatures produced can cause nitrogen and oxygen in the air to form the pollutant nitrogen dioxide.

Complete the balanced equation for the reaction.

Explain how the greenhouse effect is caused by the gases produced by the complete combustion of diesel oil.

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)

An impure hydrocarbon fuel is burned in the apparatus in Figure 7.

When the fuel is burned

the funnel becomes hot a colourless liquid forms in tube A the indicator in tube B changes colour to show an acidic gas.

Explain these observations.

*(c) Petrol and diesel are used as fuels for cars. The emissions from three similar sized cars were investigated. The first car was the oldest, had no catalytic converter and used petrol. The other two cars were only a few years old. One of these was fitted with a catalytic converter and used petrol and the other car used diesel.

Figure 9 shows the emissions in grams for each kilometre travelled by these three cars.

Discuss and compare the impact on the environment of the emissions from these three cars using the information from Figure 9.

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.