AC19: Neutralisation Flashcards
What is the equivalence point on a neutralisation graph
Where the moles of H+ = the moles of OH-
When predicting a neutralisation curve what 3 points are needed
- pH at the start
- The volume at the equivalence point
- End pH
What is the difference between a neutralisation curve with a weak and a strong acid
The cliff edge of a weak acid is less steep since the pH doesn’t reach the lower pHs
Why does a weak acid into a strong alkali not have a pH 7, at the equivalence point
Since the weak acid has a strong conjugate base, so the base picks up protons making the solution basic
Why does a weak alkali into a strong acid not have a pH 7, at equivalence point
Since the weak base has a strong conjugate acid which increase proton concentration making the solution acidic
What is the pH range of methyl orange
3.1-4.4
What is the pH range of bromothymol blue
6.0-7.6
What is the pH range of phenolppthalein
8.3-10
What colour is methyl orange in acidic solution
Red
What colour is methyl orange in more basic solution
Yellow
What colour is bromothymol blue is more acidic solutions
Yellow
What colour is bromothymol blue is more basic solutions
blue
What colour is bromothymol blue is mid solution
Greenish
What colour is phenolpthalein
Pink
What indicator is used for weak acid and weak base
No indicator
How can you work out the end point of the indicator pH, when given the pKa
pKa=pH
What is a pH meter
A probe which dips into the solution
What does a pH meter measure
Voltage and then converts it into a pH reading
What are indicators
Weak acids
Is a neutralisation reaction endo or exo thermic
Exothermic
When reading a temperature against volume of alkali graph, where is the equivalence point
When no more heat is released
What is the enthalpy change of neutralisation
The change in enthalpy when an acid and base undergo a neutralisation reaction to form one mole of water
