Composition of the atmosphereIB MYP Chemistry: Mind map

Exam questions on Composition of the atmosphere

1. A diving equipment supplier in Cape Town fills cylinders with compressed dry air. Dry air is a mixture of gases. It is mainly nitrogen and oxygen, with small amounts of argon and carbon dioxide.
   The gases other than nitrogen and oxygen make up about 1% of dry air. Name the gas that is the largest part of this 1%, and state the name of the group of elements to which it belongs.2 marks
2. A student in Mumbai measures the percentage of oxygen in air. She puts 100 cm³ of air in a gas syringe that is connected through a tube of heated copper turnings to a second, empty syringe. She pushes the air slowly back and forth over the hot copper until the volume stops changing. When the apparatus has cooled to room temperature, the volume of gas left is 79 cm³.
   Use the results to calculate the percentage of oxygen in the air sample.2 marks
3. Scientists believe that 4 billion years ago the atmosphere of the Earth contained mostly carbon dioxide, with water vapour and nitrogen released by volcanoes, and almost no oxygen. Today, carbon dioxide makes up about 0.04% of the air and oxygen makes up about 21%.
   Describe how the percentage of carbon dioxide in the atmosphere decreased as the Earth cooled.3 marks