Which pair of gases may have been present in small proportions in the Earth's early atmosphere?
Chlorine and helium
Hydrogen and helium
Methane and ammonia
Methane and chlorine
79 exam-style questions on AQA GCSE Chemistry 9.1 The composition and evolution of the Earth's atmosphere, covering 9.1.1 The proportions of different gases in the atmosphere, 9.1.2 The Earth's early atmosphere, 9.1.3 How oxygen increased, and 9.1.4 How carbon dioxide decreased. Each one has a worked solution and a mark scheme showing where the marks go.