(a(i))[1]
State the percentage of oxygen present in clean, dry air.
(a(ii))[2]
Name any two other elements in clean, dry air.
(b)[4]
Lead and sulfur dioxide are air pollutants. For each pollutant, state where it comes from and give one harmful effect of the pollutant.
(c(i))[2]
Complete the dot-and-cross diagram to show how the electrons are arranged in a water molecule.
(c(ii))[2]
Anhydrous copper(II) sulfate is used to test for water. State the colour change seen in this test.