Acids and Bases Flashcards
What is an acid
An acid is a proton donor
What is a base
A base is a proton acceptor
What is an alkali
A base that is soluble
What is a strong acid
An acid which fully dissociates into its ions
HA—–> H+ + A-
Give 4 examples of strong acids and how they dissociate
HCl —-> H+ + Cl- monoprotic
H2SO4 ———> 2H+ + SO4^2- diprotic
HNO3 ———> H+ + NO3- monoprotic
H3PO4 ———> 3H+ + PO4^3- triprotic
What is a weak acid
An acid which only slightly dissociates into its ions
HA <===> H+ + A-
Give an example of a weak acid
-All organic acids e.g. ethanoic acid CH3COOH
-Any other acid that is not a strong acid
State the 5 types of acid-base reactions
1) Acid + Metal ——–> Salt + Hydrogen
2) Acid + Metal Oxide ———-> Salt + Water
3) Acid + Metal Hydroxide ——–> Salt + Water
4) Acid + Metal Carbonate ——–> Salt + CO2 + Water
5) Acid + Ammonia ———> Ammonioum + whats left
Define pH
pH=-Log10[H+]
Rearranges to [H+]=10^-pH
How do you calculate the pH of a strong acid
EG monoprotic, diprotic
[HA]= conc of strong of strong acid
monotropic pH=-Log10[HA]
Diprotic (H2SO4) pH=-Log10[H+]—–> Ph=-log[2HA]
ect
How do you calculate the pH of a weak acid
ka= products/reactants
ka= [H+][A-]/[HA]
1:1 Ratio so
Ka= [H+]^2/[HA]
Can rearrange to fine conc of acid [H+]
[H+]=√ka[HA]
Pure water
Pure water only VERY slightly dissociates
H2O <====> H+ + OH-
How do you calculate the pH of pure water
Kw=[H+][OH-]
No H2O at bottom as this is a constant
[H+]^2= Kw
[H+]=√Kw
Why is pure water always neutral
Because [H+]=[OH-]
The conc of H+ equals to conc of OH-
Strong Alkalis
A strong acid fully dissociates
MOH—–> M+ + OH-
How do you calculate the pH of a strong alkali
Kw=[H+][OH-]
[H+]= Kw/[OH-]
[H+]= kw/[nMOH]
-n= number of OH- in formula of alkali (mono, di,tri)
Give the equation of pKa and it’s rearranged form
Define buffer solution
A buffer is a solution that can resist changes in pH when a small amount of acid or base is added
Define acidic buffer and basic buffer
Acidic buffer- Made of a weak acid and a soluble salt of that acid, maintains a pH below 7
Basic buffer- Made of a weak BASE and a soluble salt of the BASE, maintains a pH above 7
How do acidic buffers work when added to an
Acid
Base
How do basic buffers work when added to an
-acid
-base
Outline the steps in a normal titration
Outline the steps for a pH titration
Why do you need to calibrate a pH meter before use
- After storage pH meter may not produce accurate readings
- To calibrate place the pH meter in a solution of known pH and adjust the meter accordingly
What are the 4 pH titration graphs, sketch them
What are the key points of the pH titration graphs
What is the half- neutralisation point
The volume halfway between 0 and the equivalence point
It is useful when carrying out buffer calculations because:
[weak acid]=[salt]
Define equivalence point
When exactly enough acid has been added to neutralise the base (or vice versa)
Define end point
The exact volume of acid or base which needs to be added to cause an indicator to change colour
How do you know if an indicator is suitable
What would be a suitable indicator for this graph
Find Ka for the half equivalence point on this graph
