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C4 End of Topic - Coggle Diagram
C4 End of Topic
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pH and Neutralisation
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The reaction between an alkali and an acid produces a salt and water when the hydroxide ions react with the hydrogen ions.
As the pH of a solution decreases by a one unit, the hydrogen ion concentration increases by a factor or 10
The Reactivity Series
As we move down the reactivity series, the elements shown become less reactive.
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When reacting together, more reactive elements can displace less reactive element in a compound
Electrolysis
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Components
The ionic compound must first be made molten or aqueous as to allow the ions within to move, it can now conduct electricity (it is now an electrolyte)
The electrodes used are often made from carbon as it is a very good conductor because of the free electrons present in its allotropes
Typically, a 6 volt battery or cell is used as a power source during electrolysis
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Sometimes, during electrolysis, the positive carbon electrode reacts with the oxygen in the compound or in the water and CO2 is produced as a product, this means the positive electrode has to be replaced frequently. This could be prevented with the use of platinum which is a good conductor but is very low on the reactivity series,
Titrations
For Titration Calculations:
Number of Moles (mol) = Concentration (mol /dm^3) x Volume (dm^3)
Number of Moles (mol) = Mass (g) / Molar Mass(Relative Formula Mass in Grams)
If stated, to convert mol/dm^3 into g/dm^3 multiply the answer by the solution's relative formula mass.
Using a burette whilst titrating an acid or alkali allows for more accurate results when adding the solution 'drop by drop'.
Method: 1) Pipette 25.0cm^3 of alkali into a conical flask, add a phenolphthalein indicator.
2) Fill a burette with an acid of known concentration.
3) Take the initial reading on the burette and record it.
4) Swirling the flask, use a tap to add the acid into the alkali drop by drop.
5) Stop when the first permanent colour change occurs.
6) Record the final volume in the burette.
7) Repeat until titres are within 0.05cm^3
Strong and Weak Acids
A strong acid is completely ionised in an aqueous solution (Nitric, Sulphuric) whilst a weak acid only ionises partially (Citric, Carbonic)
The larger the amount of acid in a certain volume of liquid, the more concentrated the acid is.
When weak acids react, the reaction is reversable.
Reduction With Carbon
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When carbon reacts with the metal oxide, the metal loses oxygen and is therefore reduced and carbon gains oxygen, therefore being oxidised; this releases carbon dioxide and the metal as a product.
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