Acid Base Equilibria Flashcards
(19 cards)
Formula for ionic product of water
Kw = [H3O^+] [OH-]
What is the ionic product of oure water at 298K?
Kw = 1.00 x 10^-14
What happens to Kw when temperature increases?
When temperature increases, Kw increases as water dissociates at a larger extent and both H3O+ and OH- at equilibrium increases.
Formula for pH
pH = -lg[H3O+]
Formula for pOH
pOH = -lg[OH-]
Is a solution acidic if the pH of the solution <7?
No, pH is just a measure of concentration of Hydrogen ions in the solution and does not tell us the acidity of the solution. Only when [H+]>[OH-] is when the solution is acidic.
Formula of acid dissociation constant Ka
Ka = [H3O+][A-]/[HA]
How to determine the strength of the acid?
The larger the Ka value or the smaller the pKa value the stronger the acid.
Formula for base dissociation constant Kb
Kb = [OH-][BH+]/[B]
How to determine strength of base?
The larger the Kb value or smaller the pKb value the stronger the base.
What is the relationship between Ka, Kb and Kw?
Ka x Kb = Kw and pKa + pKb = pKw
Define and state the formula for degree of dissociation.
Degree of dissociation is the fraction of acid or base molecules which is dissociated into ions in water. D = amount dissociated/total initial amount
What is the degree of dissociation of strong and weak base/acid?
The degree of dissociation is close to 1 for strong acids and bases and smaller than 1 for weak acid and bases.
What is the relationship between degree of dissociation and dissociation constant?
D = square root of Kb/a / [B or HA]
and Ka/b = D^2 [HA or B]
How to calculate [H3O+] in a weak monobasic acid?
[H3O+] = square root of Ka x [HA] initial
How to calculate [OH-] in a weak monobasic acid?
[OH-] = square root of Kb x [B] initial
Define an Arrhenius Acid and Base.
An Arrhenius acid is a substance that dissociates in water to form hydrogen ions.
An Arrhenius base is a substance that dissociates in water to form hydroxide ions
Define a Bronsted-Lowry Acid and Base.
A Bronsted-Lowry acid is a proton (H+) donor.
A Bronsted-Lowry Base is a proton (H+) acceptor
