C5 - Chemical Changes
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- Created on: 14-11-17 17:52
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- The metals can be placed in order of reactivity by their reactions with water and dilute acid
- The Reactivity Series
- C5 - Chemical changes
- Displacement Reactions
- A more reactive metal will displace a less reactive metal from its aqueous solution
- The non-metals hydrogen and carbon can be given positions in the reactivity series on the basis of displacement reactions
- OIL - Oxidation is the loss of the electrons
- RIG - Reduction is the gain of electrons
- Extracting Metals
- A metal ore contains enough of the metal to make it economic to extract the metal. Ores are mined from the ground and might need to be concentrated before the metal is extracted and purified
- Gold and other unreactive metals can be found in their native state.
- The reactivity series helps you to decide the best way to extract a metal from its ore. The oxides of metals below carbon in the series can be reduced by carbon to give the metal element
- Salts from metals
- A salt is a compound formed when the hydrogen in an acid is wholly or partially replaced by metal or ammonium ions
- Salts can be made by reacting a suitable metal with an acid. The metal must be above hydrogen in the reactivity series, but not dangerously reactive
- The reaction between a metal and an acid produces hydrogen gas as well as a salt. A sample of the salt made can then be crystallized out of solution by evaporating off the water
- The reaction between a metal and an acid is an example of a redox reaction.The metal atoms lose electrons and are oxidised, and hydrogen ions from the acid gain electrons and are reduced
- Salts from insoluble bases
- When an acid reacts with a base, a neutralisation reaction occurs
- The reaction between an acid and a base produces a salt and water
- The sum of the charges on the ions in a salt adds up to zero. This enables you to work out the formula of salts, knowing the charges on the ions present
- A pure, dry sample of the salt made in an acid-base reaction can be crystallised out of solution by evaporating off most of the water, and drying with filter papers if necessary
- Making more salts
- An indicator is needed when a soluble salt is prepared by reacting an alkali with an acid
- The titration can be repeated without the indicator to make a salt, and then a pure, dry sample of its crystals can be prepared
- A carbonate reacts with an acid to produce a salt, water, and a carbon dioxide gas.
- Neutralisation and the pH scale
- Acids are substances that produce H+ (aq) ions when you add them to water
- Bases are substances that will neutralise acids
- An alkali is a soluble hydroxide. Alkalis produce OH- (aq) ions when you add them to water
- You can use the pH scale to show how acidic or alkaline a solution is
- Solutions with pH values less than 7 are acidic, pH values more than 7 are alkaline, and a pH value of 7 indicates a neutral solution
- Strong and weak acids
- Aqueous solutions of weak acids, such as carboxylic acids, have a higher pH value than solutions of strong acids with the same concentration
- As the pH decreases by one unit, the hydrogen ion concentration of the solution increases by a factor of 10
- Displacement Reactions
- Hydrogen gas is given off if metals react with water or dilute acids. The gas 'pops' with a lighted spill
- C5 - Chemical changes
- The Reactivity Series
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