When the Earth's oceans first formed, large amounts of atmospheric carbon dioxide dissolved in the water. Marine organisms incorporated the dissolved carbon into their shells and skeletons. Over millions of years, these shells compressed at the bottom of the ocean to form a sedimentary rock, permanently locking away the carbon.
What is the main chemical compound in these shells, and what is the name of the sedimentary rock formed?
Calcium carbonate (CaCO3\text{CaCO}_3CaCO3), forming sandstone
Silicon dioxide (SiO2\text{SiO}_2SiO2), forming limestone
Calcium carbonate (CaCO3\text{CaCO}_3CaCO3), forming limestone
Calcium sulfate (CaSO4\text{CaSO}_4CaSO4), forming gypsum
Practise Edexcel GCSE Chemistry Earth and atmospheric science with exam-style questions for Foundation and Higher tier. 62 questions, matched to the Edexcel GCSE Chemistry (1CH0) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
