Neutralisation
Acid + Base → Salt + Water
H2SO4 + 2NaOH → Na2SO4 + 2H2O
When an acid and a base react in exact quantities to ‘cancel’ each other out.
Exactly how many moles of NaOH will neutralise exactly 1 mole of sulphuric acid?
Titrations
An experiment that can measure exact reacting volumes which can help determine the concentrations of unknown solutions.
Example of How a Titration Works
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In the burette a solution of unknown concentration is placed e.g. H2SO4 → |
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In the conical flask, a known volume of a solution with a known concentration e.g. 25cm3 of 0.1moldm-3 NaOH → |
Also essential is an indicator. This will show a certain colour when the solution is exactly neutral.
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The solution in the burette is added slowly
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The total volume added can be read off the burette → |
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When the colour of the indicator changes permanently you must stop adding the solution in the burette. → |
So using the following neutralisation reaction: H2SO4 + 2NaOH → Na2SO4 + 2H2O
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H2SO4 + |
2NaOH → |
Na2SO4 + |
2H2O |
| Before the experiment: |
Volume: ? |
Volume: 25cm3 |
In titration experiments you do not care about the volumes or concentrations of the products.
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| Conc: ? |
Conc: 0.1moldm-3 |
| After the experiment: |
Volume: Given from Burette Reading cm3 |
Volume: 25cm3 |
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| Conc: ? |
Conc: 0.1moldm-3 |
Here is an example of some results: H2SO4 + 2NaOH → Na2SO4 + 2H2O
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H2SO4 + |
2NaOH → |
Na2SO4 + |
2H2O |
| Before the experiment: |
Volume: ? |
Volume: 25cm3 |
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| Conc: ? |
Conc: 0.1moldm-3 |
| After the experiment: |
Volume: 18cm3 |
Volume: 25cm3 |
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| Conc: ? |
Conc: 0.1moldm-3 |
Find the unknown concentration of the sulphuric acid
Answer
5 Steps:
- Write balanced equation.
- Find the moles of the substance you know the most about.
- Find the ratio of acid to base from the equation.
- Convert the number of moles you have from 2 using ratio into the actual moles used.
- Convert the actual moles into concentration using the volume.
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