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Topic 3a -Acids Bases and Salts - Coggle Diagram
Topic 3a -Acids Bases and Salts
Making salts
Soluble salts
1) Gently heat sulfuric acid in a water bath
2) Add copper oxide and sir until it is in excess
3) This shows the acid is neutralised and the reaction is finished
4) Filter out the excess coppper oxide from the copper sulphate to make sure there is no contamination
5) After filtration, crystalize the copper sulphater solution by evapouration
6) Once salt starts to form, stop heating and leave to cystalize, it is now a pure soluble salt
Making copper sulphate
We add excess to ensure the acid reacts completely
The remaining solution is salt and water only because the acid has fully reacted and the other product has been filtered
We filter out the excess reactant so that you are left with just salt and water
Insoluble salts
1) Mix two solutions together, lead nitrate and sodium cholride, a salt will form as a precipitate
2) Set up a filtration process
3) Pour the solution through the funnel
4) Once any excess water is drained, wash the salt (lead chloride) using distilled water
5) Leave the salt out to dry
Acids
Weak Acids
Only partially dissociate in water, only some of the molecles realease H+ ions
Carboxylic acids are weak acids, like citric and carbonic acids
Weak acids tend to have a pH of around 2-6
Ionisation of a weak acid is reversible
Strong acids
Almost completely dissociate in water
Sulfuric acid and nitric acid
pH of 0-2
Higher concentration of H+ ions than a weak acid
When acids are added to an aqueous solution, they ionise, the strength of an acid tells you about the proportion of acid particles that will dissociate
Acid strength
An acid with a high volume of water compared to the acid is dilute
The more grams of acid per dm3, the more concentrated
A concentrated solution has a greater amount of dissolved solute particles than a dilute solution
Acid strength tells you the proportion of water to acid molecules
You can change the concentrated solution into a dilute solution by adding more water to it
You can change a dilute solution into a concentrated solution by dissolving more solute in it or evapourating some of the water
Source of hydrogen ions .
Concentration
When an acid is in solution, a higher concentration of H+ ions means the solution is more acidic, thus having a lower pH
When an alkali is in solution, a higher concentration of OH- ions means that the solution is more alkaline, thus having a higher pH
Concentrated = larger amount of substance in a given volume
Dilute = less amount of substrance in a given volume
pH indicators
Methyl orange
Red in acid
Peach in neutral
Yellow in alkaline
Litmus
Red in acid
Blue in alkaline
purple in neutral
Phenolphthalein
colourless in acid
colourless in neutral
bright pink in alkaline
Reactions
Neutralisation reactions
H+(aq) + OH-(aq) --> H20(l)
Solution formed in neutral
At pH 7, the concentration of OH- ions equals the concentration of H+ ions
Acid + Base --> Salt + Water
Method
Add some dilute HCl into the beaker
Measure and record the pH of the contents of the beaker
Add a small madd of calcium hydroxide powder, stir and then measure and record the pH again
Repeat until the pH no longer changes
Reactions with metals
Acid + Metal --> metal salt + hydrogen
Metals react with acids to produce a salt and hydrogen only
Reactions of acids
Acid + Metal hydroxide --> Salt + Water
Reactions with metal carbonates
Acid + Metal carbonate --> Metal Salt + CO2 + H2O
Metal carbonates react with acids to produce a salt, water and carbon dioxide only
Solubility rules
Carbonates
Soluble = Ammonium, Potassium, Sodium Carbonate
Insoluble = All others
Hydroxides
Soluble = Ammonium, Potassium, Sodium Hydroxide
Insoluble = All others
Chlorides
Insoluble = Lead and Silver Chloride
Soluble = All others
Sulphates
Insoluble = Barium, Calcium, Lead Sulphate
Soluble = All others
Nitrates
All Soluble
Tests
Test of CO2
Limewater test
Bubble the gas through limewater
If it turns cloudy, then CO2 is present
Caused by Calcium carbonate forming
Test for Hydrogen
Squeaky pop test
Light a splint and put it at the open end of a test tube
If you hear a squeaky pop, then there is hydrogen present
Noise comes from hydrogen burning in the air with the oxygen
Concentration and pH
Concentration meansures how much acid there is in a litre of water
If the concentration of H+ ions decreases by X10, the pH decreases by 1
Base
Any substance than reacts with an acid to from salt and water only
Metal hydroxides and metal oxides