chem - separate chem I (5)

• Transition metals have a high melting point due to electrostatic forces between + charged metal ions and electrons.
• Transition metals have a high density.
• Transition metals have ions with many different charges.
• Transition metals form coloured compounds.
• Transition metals are useful as catalysts, shown by iron and its use in the Haber process as a catalyst.
• Corrosion is the destruction of materials by chemical reactions with substances in the environment.
• Rusting is a type of corrosion that occurs when both air and water are necessary for iron to rust, resulting in oxidation.
• Rusting can be prevented by excluding oxygen and water, for example, by painting, coating with plastic, or using oil/grease.
• Aluminium has an oxide coating that protects the metal from further corrosion.
• Water can be kept away using a desiccant in the container, which absorbs water vapour.
• Oxygen can be kept away by storing the metal in a vacuum container.
• Sacrificial protection involves the metal you’re protecting from rusting being galvanised with a more reactive metal that will rust first and prevent water and oxygen reaching the layer underneath.
• Electroplating acts as a barrier to exclude oxygen and water.
• Alloys are mixtures of similar metals used for everyday use.
• In a pure metal, all the + metal ions are the same size and in a regular arrangement, making the metal soft/malleable.
• In an alloy, you have + ions of different metals, which have different sized ions, disrupting the regular structure and preventing the ions from sliding as easily, leaving a stronger metal.
• Steels are alloys since they use mixtures of carbon and iron.
• Some steels contain other metals.
• Alloys can be designed to specific uses, for example, low-carbon steels are easily shaped and used for sheeting, while high carbon steels are hard and used for cutting tools.
• Stainless steels, containing chromium and nickel, are resistant to corrosion and used for cutlery.
• Aluminium has a low density and is used for aircraft.
• Copper is a good conductor and is used in electrical cables.
• Gold has good resistance to corrosion and is used in jewellery.
• In industry, the reactants for the Haber process are natural gas, air, water (ammonia) and sulphur, air, water (sulphuric acid), and the process is large scale and involves many stages.
• A chemical cell produces a voltage until one of the reactants is used up.
• The overall reaction in a hydrogen-oxygen fuel cell is the oxidation of hydrogen to produce water 2H2 + O2 → 2H2O.
• The equation for the volume of 1 mol of any gas at RTP (room temperature and pressure: 20 degrees C and 1 atmosphere pressure) is Volume (dm3) of gas at RTP = Mol x 24.
• Chemical reactions stop when one of the reactants has been used up.
• If a balanced equation is given, the mass/volume of a reactant can be calculated using moles.
• Atom economy is a measure of the amount of starting materials that end up as useful products.
• Avogadro's law states that one mole of a substance contains 6.02 x 1023 particles.
• Equilibrium is reached at a faster rate when a higher temperature is used, a higher pressure/concentration is used, a catalyst is used, or a combination of these factors is used.
• Actual yield is less than theoretical yield due to incomplete reactions, practical losses during the experiment, and side reactions.
• In a hydrogen-oxygen fuel cell, hydrogen and oxygen are used to produce a voltage and water is the only product.
• The concentration of an alkali can be calculated using concentration = mol/volume.
• The amount of product obtained is known as yield.
• If 10 moles of a substance are present, there would be 10 x 6.02 x 1023 particles = 6.02 x 1024 particles.
• Compounds of nitrogen, phosphorus, and potassium are fertilisers that improve agricultural productivity.
• In the lab, the reactants for the Haber process are ammonia solution and dilute sulfuric acid, which are bought from chemical manufacturers, and the process is small scale and involves a few stages.
• If both concentrations and volumes are known, the percentage yield can be calculated as Amount of product produced/Maximum amount of product possible x 100.