NYGH O’ Level Database Questions for Practice and Revision_Chemistry

1 Chem!stry Name: …………………… ( ) Class: ……………… Date: …… / …… / …… O’ Level Database Questions for Practice and Revision • Note: A link to the answers is given on pg. 47. A copy of the Periodic Table is given on pg. 48. Question 1. This graph shows how the percentage of three of the gases in the Earth’s atmosphere has changed over five thousand million years. Use the information from the graph to answer the following questions. (a) (i) How long have the percentages of all gases in the atmosphere remained unchanged? …………………………………………………………………………………………………… (ii) Name gas 3. Give a reason for your answer. [3] …………………………………………………………………………………………………… ……………………………………………………………………………………………………

2 (b) (i) Describe how the percentages of carbon dioxide and oxygen have changed. …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… (ii) Suggest an explanation for the changes that have taken place in carbon dioxide and oxygen percentages, identifying the processes involved and giving equations for any reactions. [7] …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… [Total: 10]

3 Question 2. Read the information about the chlorides of the elements in Period 3 of the Periodic Table. Elements and their Chlorides The formulae and chemical properties of the chlorides of the elements change across Period 3. The chlorides behave differently when they are added to water. Some of the chlorides dissolve in water to form a solution. Some hydrolyse when they are added to water. This means that they react chemically with water to produce new products. element metal or non- metal formula of main chloride bonding in chloride effect of adding chloride to water products of adding chloride to water Na metal NaCl ionic dissolves NaCl(aq) Mg metal MgCl2 ionic dissolves MgCl2(aq) Al metal AlCl3 covalent hydrolyses complex mixture of products including HCl(aq) Si non-metal SiCl4 covalent hydrolyses SiO2(s) HCl(aq) P non-metal PCl3 covalent hydrolyses H3PO3(a