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Chemistry C4 (Electrolysis: (Metal electrolysis: (Ionic half equations can…
Chemistry C4
Electrolysis:
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An electronic current is tased through an electrolyte. The electrolyte is a molten or dissolved ionic compound. The positive ions move towards the elctrons, where they react, and the compound decomposes. The positive ions move to the cathode and gain electrons. The negative ions move towards to anode where they lose electrons. This creates a flow of charge as the ions travel through the electrolyte.
An ionic solid can't be electrolysed, it must be dissolved or molten. This means the ions can move freely and conduct electricity.
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Metal electrolysis:
Metals can extract from their ores using electrolysis. If a metal is to reduce carbon or reacts with carbon, Electrolysis can be used. It is very expensive as lots of energy is required to melt ores.
Ionic half equations can be used as notation for the reactions occurring at either the cathode or anode during electrolysis
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At the positive electrode: If the negative ion from the ionic compound is simple (eg Cl- or Br-), then that element is produced. If the negative ion is a complex ion (eg NO3-, SO42-, CO32-), then oxygen is produced from the hydroxide ion present instead.
At the negative electrode: Metal ions and hydrogen ions are positively charged. Whether you get the metal or hydrogen during electrolysis depends on the position of the metal in the reactivity series.
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Acids and Bases:
The Ph scale:
Goes from 0 to 14, with 0 being highly acidic and 14 being highly alkaline. A universal indicator can be used to measure the Ph of a solution.
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Neutralising
Acids and Bases neutralise one another, A base is any substance that will react with an acid to form a salt.
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Strong acids, Weak Acids and their reactions:
Acids can be strong or weak. Strong acids ionise completely in water. All the acid particles dissociate to release h+ ions.
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The Ph is a measure of the concentration of H+ ions in the solution.
For every Ph decrease of 1, the concentration of H+ ions increase by a factor of 10
Strong acids are not concentrated acids! Concentration is a measure of how much acid there is in a volume of water. Acids can be dilute or concentrated. Ph will decrease with an increase in concentration regardless of how strong or weak the acid is
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Redox reactions:
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REDuction and Oxidation happen at the same time, Hence the name REDOX reactions
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