(a)[1]
Name the catalyst involved in this reaction.
(b)[1]
Draw a ‘dot-and-cross’ diagram for an oxygen molecule. Include only the outer-shell electrons.
(c(i))[3]
Describe how, and explain why, the percentage yield of sulfur trioxide varies with temperature.
(c(ii))[2]
Suggest why the reaction is carried out at 450$^\circ$C and not at 250$^\circ$C.
(d)[2]
Describe how, and explain why, the position of equilibrium changes when the pressure increases.
(e)[1]
Sulfur trioxide oxidises hydrogen bromide to produce sulfur dioxide, bromine and water. Construct the equation for this reaction.