Air Quality & Climate (Cambridge O Level Chemistry)

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The major gases in unpolluted air are 79% nitrogen and 20% oxygen.
 

Two common pollutants in air are carbon monoxide and the oxides of nitrogen.
 

This question is concerned with the following oxides.

Two of the oxides are responsible for acid rain.

Identify the two oxides and explain their presence in the atmosphere.

Lithium oxide is an ionic compound.

When nitrogen dioxide is cooled, it forms a yellow liquid and then pale yellow crystals. These crystals are heated and the temperature is measured every minute. The following graph can be drawn.

Nitrogen dioxide and other oxides of nitrogen are formed in car engines.

Nitrogen dioxide, oxygen and water react to form dilute nitric acid.

Describe how lead(II) nitrate crystals could be prepared from dilute nitric acid and lead(II) oxide.

The reactions in this question are all examples of photochemical reactions.

Explain the phrase photochemical reaction.

Many millions of years ago, the Earth’s atmosphere was rich in carbon dioxide and contained negligible amounts of oxygen. After the appearance of green plant-like bacteria, the proportions of these two gases in the atmosphere changed.

Minimising air pollution is essential for health and for the environment.

Natural gas is methane.

Low sulfur fuels are being introduced. Ordinary diesel contains 500 ppm of sulfur but low sulfur diesel contains less than 50 ppm. Why is this an advantage to the environment?

Catalytic converters reduce pollution from motor vehicles, as shown in the following diagram.

Coal is a solid fossil fuel.

Name two other fossil fuels.

Two of the elements present in a sample of coal are carbon and sulfur. 

A sample of coal was heated in the absence of air and the products included water, ammonia and hydrocarbons.

Name three other elements present in this sample of coal.

Sulfur, present in coal, is one major cause of acid rain. Sulfur burns to form sulfur dioxide which reacts with rain water to form sulfuric acid.

In 2010, a large coal-burning power station in the UK was converted to burn both coal and wood.

Explain why the combustion of wood rather than coal can reduce the effect of the emissions from this power station on the level of carbon dioxide in the atmosphere.

The properties of five alkenes at room temperature are shown in the table.

When propene undergoes incomplete combustion, carbon monoxide is formed.

What condition is needed for incomplete combustion?

Give one adverse effect of carbon monoxide on health.

Carbon dioxide and water vapour are greenhouse gases found in air.

Draw the dot-and-cross diagram to show the bonding in a molecule of carbon dioxide. Only show the outer shell electrons.

Some power stations burn methane, CH₄.

Construct the equation to show the complete combustion of methane. 

The carbon dioxide made in power stations can be removed by a reversible reaction with water.

CO₂(g) + H₂O(l) ⇋  H₂CO₃(aq)

The forward reaction is exothermic.

Carbonic acid, H₂CO₃(aq), is a weak acid.

Air contains a mixture of gases including the noble gases neon, argon, krypton and xenon. These noble gases are monatomic elements.

State what is meant by monatomic.

State why noble gases are unreactive.

State why fractional distillation can be used to separate a liquid mixture of neon, argon, krypton and xenon.

State which noble gas, neon, argon, krypton or xenon, has the fastest rate of diffusion at 20 °C.

Explain your answer.

Air also contains oxides of nitrogen that are pollutants.

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Clean dry air contains mainly nitrogen and oxygen.

Name two other gases that are in clean dry air.

Air often contains pollutants.

Identify three common gaseous pollutants in air and state how each of these pollutants are produced.

pollutant gas 1 ..................................................
how it is produced ..................................................

pollutant gas 2 ..................................................
how it is produced ..................................................

pollutant gas 3 ..................................................
how it is produced ..................................................

Air is a mixture of gases.

The main constituents are the elements oxygen and nitrogen.

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Common pollutants present in air are the oxides of nitrogen and sulfur dioxide.

The percentage of oxygen in air can be determined by the following experiment.

The gas syringe contains 50 cm³ of air. The large pile of copper is heated and the air is passed from one gas syringe to the other over the hot copper. The large pile of copper turns black. The gas is allowed to cool and its volume measured. The small pile of copper is heated and the remaining gas passed over the hot copper. The copper does not turn black. The final volume of gas left in the apparatus is less than 50 cm³.

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Plant growth is improved by the availability of essential elements, such as nitrogen, and by the soil having a suitable pH.

Nitrogen-based fertilisers are made from ammonia. Ammonia is manufactured by the Haber process.

Crops do not grow well if the soil is too acidic.

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Polluted air contains two oxides of carbon and two oxides of nitrogen. A major source of these pollutants is motor vehicles.

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Predict the possible adverse effect on the environment when this non-metal oxide, NO_2, reacts with water and oxygen.

How are the amounts of carbon monoxide and nitrogen monoxide emitted by modern motor vehicles reduced?

Include an equation in your answer.

Three common pollutants in the air are carbon monoxide, the oxides of nitrogen, NO and NO₂ and unburnt hydrocarbons. They are all emitted by motor vehicles.

Describe how the oxides of nitrogen are formed.

Describe how a catalytic converter reduces the emission of these three pollutants.

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The burning of fossil fuels is largely responsible for the formation of acid rain. Two of the acids in acid rain are sulfuric acid and nitric acid.

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