Sec 4 Chemistry Maintaining Air Quality topical questions

State the approximate percentage by volume of each gas in clean, dry air.

1. (a)Nitrogen[1]
2. (b)Oxygen[1]
3. (c)Carbon dioxide[1]

Name the pollutant gas produced when each fuel burns in a limited air supply, and state one effect of each.

1. (a)Coal containing sulfur impurities → gas and one effect[2]
2. (b)Petrol in a badly tuned engine → gas and one effect[2]

Write the equation for the reaction catalysed inside a catalytic converter between nitrogen monoxide and carbon monoxide.

Name two greenhouse gases.

Complete the pollutant table with the source and one harmful effect of each gas.

1. (a)Give the source and one effect for CO.[2]
2. (b)Give the source and one effect for SO₂.[2]

Write balanced equations for three combustion reactions.

1. (a)Carbon (coke) burning in oxygen.[1]
2. (b)Carbon monoxide burning in oxygen.[1]
3. (c)Methane burning completely in oxygen.[1]

Describe an experiment to determine the percentage of oxygen in a sample of air, including the readings taken and the calculation.

Explain, with equations, how sulfur dioxide from a power station becomes acid rain, and state two effects of acid rain.

Explain why the level of carbon dioxide in the atmosphere is rising, and why this raises the average temperature of the Earth.

A city installs catalytic converters on all its vehicles. Predict which pollutant levels fall, which gas rises slightly, and why the change is still worthwhile.

Explain why burning methane (natural gas) is considered cleaner than burning coal, even though both release carbon dioxide.

Excess hot copper foil is placed in a tube and 100 cm³ of air is drawn through it several times until the syringe reading no longer falls. It settles at 79 cm³.

1. (a)Calculate the percentage of oxygen in the sample.[1]
2. (b)Explain why the copper must be in excess and heated.[2]
3. (c)State what remains in the 79 cm³.[1]

Atmospheric carbon dioxide measurements are summarised below.

1. (a)Describe the trend shown by the data.[1]
2. (b)Calculate the average rise per decade over the whole period.[1]
3. (c)Explain how rising CO₂ raises the Earth’s average temperature.[2]
4. (d)Name one consequence of the warming.[1]

A car’s exhaust gases pass through a catalytic converter coated with platinum and rhodium.

1. (a)Write the equation for the main reaction inside the converter.[1]
2. (b)Explain why the gases must be hot for the converter to work.[1]
3. (c)Explain why installing millions of converters still cannot stop global warming.[2]

A power station burns coal; its flue gas contains SO₂. A scrubber sprays the flue gas with powdered limestone suspended in water.

1. (a)Write the equation for the scrubber reaction.[2]
2. (b)Explain why the reaction is an acid–base (neutralisation) style reaction.[2]
3. (c)State what must be done with the calcium sulfite product, and name one difficulty of the process.[2]

Explain why the catalytic converter and the flue-gas scrubber each solve only part of the air-quality problem of fossil fuels.

Air from two cities is tested. City A has high SO₂ but low NOx; city B has low SO₂ but high NOx and unburnt hydrocarbons.

1. (a)Suggest the dominant fuel or activity in each city.[2]
2. (b)State which city suffers more building erosion on limestone monuments, with an equation.[2]
3. (c)State which city more likely suffers summer smog, with a reason.[2]

A transport minister must decide between petrol cars and electric cars charged from the national grid.

1. (a)State which exhaust pollutants disappear immediately with electric cars.[2]
2. (b)Explain why electric cars may still cause CO₂ emissions.[2]
3. (c)State one condition under which the electric fleet becomes nearly CO₂-free, with a reason.[2]