Acids and bases Flashcards
Define acid:
A substance that donates a proton
Define Base
Substance that accepts a proton
Define alkali:
A substance that produces OH- in water.
Define conjugate acid:
Species formed from the acceptance of a proton by the base
Define conjugate base:
Species formed from the removal of a proton from the acid.
Write 2 equations to show how water is amphoteric:
HCL + H2O –> H3O+ + Cl-
NH3 + H2O –> NH4+ + OH-
What does it mean if we have a larger Ka value?
The stronger the acid.
Equilibrium lies more to the right.
Why do data books not contain Ka values for strong acids?
Strong acids completely disassociate so there’s no equilibrium.
When completing an acids and bases question with weak acids and strong bases, what must we remember?
We calculate the number of moles assuming there is no disassociation, so we don’t consider the salt produced.
You do the calculation the same as strong acid and strong bases.
What is the definition of a buffer solution?
A solution that resists changes in pH when small amounts of acid, alkali or water are added to it.
The pH does change, just not by a lot.
An acidic buffer solution contains:
Give an example
- A weak acid
- A salt of the weak acid
A buffer solution needs lots of HA and A- in the solution.
Ethanoic acid and sodium ethanoate
What are the 2 ways of making a buffer solution?
Why does method 2 make a buffer solution?
1- Directly dissolving a salt of the weak acid in a solution of the acid.
2- Adding a strong base to an excess of weak acid.
Acid + base will make a salt. If the acid is in excess, there will be lots left over, therefore you get the HA and the A-.
