BMAT PREP CHEMISTRY QUESTIONS AND ANSWERS

SALTS All solid salts consist of positive and negative ions, and some of them contain water molecules as well. The water in a lattice is called water of crystallisation. One mole of a hydrated salt always has a certain number of moles of water of crystallisation shown in the formula. For example, hydrated copper sulphate (CuSO4.5H2O) has five moles of water for each mole of the salt. GROUP 1 Group 1 elements are alkali metals. They are metals that are usually stored under oil or argon to stop them from reacting with the air. They have to be handled with care because the products of their reaction with air or water are corrosive. They all react with water to form an alkaline solution, producing hydrogen gas and the metal hydroxide. Alkali metals all react with oxygen to form an oxide. When this happens, they tarnish and lose their shininess. GROUP 7 Group 7 elements are the halogens. They are colourful non-metals Fluorine-yellow gas chlorine-dense green gas bromine - dense red brown liquid iodine- dark grey solid or purple vapour GROUP 8 Group 8 are the 'Noble Gases'. These elements are inert, non-flammable, colourless gases. Noble Gases have very low boiling points as their atoms are not bonded together and there are only very weak forces between them. Going down the group, the boiling point increases as the atoms get heavier and the forces between the atoms increase. The density also increases as we move down the group. USES OF NOBLE GASES Argon is used to make filament lamps. It can also be used to protect metals that are being welded. The inert atmosphere stops the hot metal reacting with oxygen. Helium is less dense than air, so if a balloon is filled with helium gas, it will float. Helium balloons are popular decorations at parties. Helium is also used in airships. REDUCTION PROCESS Chemical reactions, such as reduction, can be used to extract metals from their ores. In the reduction process, oxygen is removed from the ore, to give the native metal. This is done by smelting the ore (heating it in a furnace).