Acids & Bases Flashcards
What is a buffer solution?
A solution containing a weak acid and its salt
What happens when an alkali is added to a buffer solution?
The weak acid dissociates to form H+ ions. These react with OH- ions to form water molecules, therefore the H+ ions are removed, however as the H+ ions are removed more weak acid dissociates to replace the lost ions and so the pH is maintained
What happens when an acid is added to a buffer solution?
The H+ ions from the acid react with the CH3COO- ions provided by the salted the weak acid
Give the rearranged Ka equation for buffers?
[H+] = Ka [HA] / [A-]
Give the pH equation
pH= -log[H+]
Special case - in buffer solution, if the conc of [HA] and [A-] are the same what can we deduce about pKa and pH?
If [HA] = [A-] Then they cancel out in the Ka equation Then we can assume pH = pKa So we use the pKa = -log[Ka]
According to Bronsted-Lowry law, what is an acid and what is a base?
An acid is a proton donor
A base is a proton acceptor
What is the conjugate acid/base pair in the forward reaction for this example?
HA + H2O —> H30+ + A-
HA is the acid as it is donating H+ to water, therefore A- is its conjugate base
Water is the base as it is accepting proton from HA, therefore H3O- is its conjugate acid
What is a strong acid
An acid which completely dissociates
What is a weak acid
An acid which only partly dissociates
Give an example of three strong acids
HCl
HNO3
H2SO4
Give an example of a weak acid
Ch3COOH
What is pH
A measure of the concentration of hydrogen ions in solution
