Chemistry 3_ acids, bases and titration.txt
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- What did Arrhenius do?
- Noticed that some substances become ionised when dissolved in water. Acids produce H+ ions and bases produce OH- ions.
What did Arrhenius NOT explain?
That some acid/base reactions work in different solvents or with no solvents at all.
Why was Arrhenius' explanation not readily accepted like Bronsted and Lowry's?
- There was not enough evidence
- No previously proven theory of ion formation
- Lack of communication/technology
- His idea did not work for ammonia gas
Bronsted and Lowry defined an acid (H+) as...
A proton donor
Bronsted and Lowry defined a base (OH-) as...
A proton acceptor
Who defined acids and bases as proton donors and acceptors?
Bronsted and Lowry
On litmus, acids turn it...
On litmus, alkalis turn it...
pH tells us?
How strong and acid or alkali is
SALT + WATER
ACID + ALKALI =?
SALT + WATER
Acid + metal =?
Salt + hydrogen
Acid + metalCARBONATE =?
salt + CARBON DIOXIDE + water
What must be present for a substance to ACT as an acid or base?
Acids produce what in aqueous solution?
H+, in water this is represented as H+(aq)
An alkali is...
A base in an aqueous solution
Which ion is produced by alkalis in aqueous solution?
Acids and alkalis are classified by...
How much they ionise in water.
What does the term 'strong' mean on terms of acids and alkalis?
One that is completely ionised in water
In what situation can acids not donate a proton?
If there is no appropriate alkali (proton acceptor), the acid cannot donate a proton
What does the term 'weak' mean on terms of acids and alkalis?
It is only partially ionised.
List 3 STRONG ACIDS
- Hydrochloric acid
- Sulphuric acid
- Nitric acid
List 2 STRONG ALKALIS
- Sodium hydroxide
- Potassium hydroxide
List 3 WEAK ACIDS
- Ethanoic acid
- Citric acid
- Carbonic acid
List 1 WEAK ALKALI
You can use titration to find out....
How much of an acid it takes to neutralise an alkali
Show the neutralisation equation (which happens in titration)
H+(aq) + OH-(aq) = H2O(l)
The benifit of titration is...
Volumes are measured fairly precisely
The end point in titration is...
The point at which the acid and alkali have reacted completely
Which indicator is usually used for titration?
Phenolphthalein (it is pink in alkali and goes colourless in acidic or neutral solution)
Summarise titration in 7 MAIN POINTS
- Wash/rinse pipette in the alkali you are using.
- Use it to measure a KNOWN AND ACCURATE volume of alkali.
- Place the alkali in a clean CONICAL FLASK and add an indicator, usually PHENOLPHTHALEIN.
- Put acid in acid-rinsed BURETTE and take the initial reading.
- Carefully add it until the solution is neutral. Take a final reading.
- Calculate the volume of acid added (initial minus final reading).
What can be done in titration to check results?
Method can be repeated
STRONG acid + STRONG alkali =(which indicator?)
Any. Universal, litmus, methyl orange, phenolphthalein...
STRONG acid + WEAK alkali =(which indicator?)
WEAK acid + STRONG alkali =(which indicator?)
To calculate concentrations in titration (write the formula)
- When a=acid and b=base, M=moles and V=volume
- Ma x Va = Mb x Vb
What would you like to do?
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