Acids and base Flashcards
HCl
Acid
H2SO4
Acid
HNO3
Acid
CH3COOH
acid
KOH
Base
NaOH
Base
Ba(OH)2
Base
What is the general equation for a neutralisation reaction?
Acid+ base —>salt + water
When an acid + metal react what do they form?
Salt+ hydrogen
When an acid and metal oxide react what do they form?
Salt + water
When an acid and metal carbonate react, what do they form?
Salt + carbon dioxide + water
What is the Arrhenius model?
Acids and bases are defined based on how they dissolve in water.
Arrhenius acids?
Dissociate to give
H+ ions
Arrhenius bases?
Dissociate to give
OH- ions
What is the brondsted Lowry model?
Acids and bases are defined based on how they react
Bronsted Lowry acid?
Proton donator
Bronsted Lowry base?
Proton acceptor
Define acidity?
Concentration of H+ ions
How do you find pH?
pH= -log10[H+]
How do you find concentration of H+ ions form pH?
[H+]=10^-pH
What does water dissociate into?
H2O=H+ + OH-
What is the equilibrium constant for water dissociation?
Kw
(Ionic product of water)
What unit does Kw have?
Mol2 dm-6
How does temperature affect pH?
The ionisation of water is endothermic. So increasing the temperature shifts the equilibrium to the right. This increases the concentration of H+ ions and so decreases the pH.
Explain how Kw increases as temperature increases?
The ionisation of water is endothermic p so increasing temperature shifts the equilibrium to the right. This increases the concentration of H+ and OH- ions, which increases Kw.
How does the low solubility of some group 2 hydroxide affect pH?
Some group 2 has low hydroxides have low solubility as a result salts don’t fully dissolve and leading to a pH value which isn’t always as high as expected.
Why is water always neutral?
As the concretatuon of OH- and H+ ions are equal
When weak acids dissociate what do they form?
Dynamic equilibrium
What is the equilibrium constant for this reaction?
Ka
(Acid dissociation constant
What is the unit for Ka?
Mol dm-3
The larger the Ka for an acid….
The stronger the acid
To make it easier to compare Ka values what is used
pKa value is used
How do you find pKa?
pKa =-log(Ka)
How do you find Ka from pKa?
10-pKa
The smaller the pKa value..
The stronger the acid is
What is an monoprotic acid?
Produces 1 proton.
Examples of monoprotic acids
HCl
HNO3
CH3COOH
What is a diprotic acid?
Produces 2 protons
Examples of diprotic acids
H2SO4
What is a triprotic acid?
Produces 3 protons
Which proton dissociates strongly?
1st proton
Which proton dissociates weakly ?
2nd and 3rd
How do you find pH after a neutralisation reactions?
Find which reactant is in excess.Calculate the amount of the excess reactant once the reaction is complete. Use your answer to step 2 alongside the volume to find concentration of [H+]or [OH-].
Find pH.
What is a buffer solution?
A buffer solution resists changes in pH when small amounts of acid or base are added.
What do buffer solutions contain?
Must containHA and A-
The concentration of HA and A- must be high.
How to make a buffer solution?
Mixing a weak acid with the salt of its conjugate base.
Or partially neutralising a weak acid with a strong base.
Equation of a buffer solution.
HA= H+ + A-
What happens when small amounts of acid or base are added to the buffer?
The equilibrium position shifts to maintain the concentration of H+.
Adding acid to a buffer solution
Adding HCl increases the concentration of H+ ions which makes the equilibrium shift to the left. This decreases the concentration of H+
Adding a bases to a buffer solution.
Add NaOH.
OH- + H+—>H2O
this decreases the concentration of H+ ions so the equilibrium shifts to the right. D increase the concentration of H+