Chapter 21 (Acid, Bases and Buffers) Flashcards
Define Bronsted-Lowry acid
A substance the can donate a proton
Define Bronsted-Lowry base
A substance that can accept a proton
Give the equation for calculating pH
-log [H+]
What are strong acids?
Acids where the H+ ions are completely dissociated
How many decimal places should pH value have?
2
What is the equation for finding the concentration of H+?
10^-pH
What is the ionic equation for water?
H2O(l) ⇌ H+(aq) + OH-(aq)
What is the equation used for water and aqueous solutions?
Kw = [H+][OH-]
What is the equation used for pure water?
Kw = [H+]²
What is the equation for weak acids and buffer solutions?
Ka = [H+][A-]/[HA]
What is the equation for a weak acid with nothing else added?
Ka = [H+]²/[HA]
OR
[H+] = √ (Ka x [HA])
What is the equation for a half neutralised weak acid?
Ka = [H+]
OR
pH = pKa
How do you find pKa?
-log(Ka)
How do you find Ka?
10^-pKa
What is the equation for the pH of a strong acid?
-log[H+]
What is the equation for the pH of a diluted strong acid?
[H+]old x (old vol/new vol) = [H+]
-log [H+}
What is the equation for the pH of a strong base?
[H+] = Kw/[OH-]
-log [H+}
What is the equation for the pH of a diluted base?
[OH-] = [OH-]old x (old vol/new vol)
[H+] = Kw/[OH-]
-log [H+}
What is the equation for pH of a weak acid?
[H+] = √ (Ka x [HA])
-log [H+}
What is the equation for pH of half neutralised weak acid?
Ka = [H+]
-log [H+}
What is the equation for the pH of water?
√ Kw = [H+]
-log [H+}
How do you find the pH of a strong acid and base solution?
1) Calculate moles of H+
2) Calculate moles of OH-
3) Find which is in excess
If H+ in excess
Moles of XS H+/Total volume
-log [H+}
If OH- in excess
Moles of XS OH-/Total volume
[H+] = Kw/[OH-]
-log [H+}
How do you find the pH of a buffer solution?
[H+] = Ka x ([HA]/[A-])
-log [H+]
How do you find the pH of a weak acid and base solution?
1) Calculate moles of HA
2) Calculate moles of OH-
3) Find which is in excess
If HA in excess
[HA] = (initial OH moles-moles of OH- added)/Total volume
[A-] = Moles of OH- added/total volume
[H+] = Ka x ([HA]/[A-])
-log [H+]
If OH- is in excess
[OH-] = Moles XS of OH-/Total volume
[H+] = Kw/[OH-]
-log [H+]
