pH Flashcards
what is a proton?
H+ ion
what is pH?
logarithmic scale which measures the concentration of H+ ions in a solution
how is pH calculated?
-log10[H+]
how is [H] from pH calculated?
10-pH
what is the assumption of strong acids and bases when calculating pH?
they dissociate fully into H+ and OH- ions
base/acid conc = [ion]
calculate the pH for [H] 0.01
-log(0.01 = 2
calculate the pH for [H] 16.2x10-13
-log(16.2x10-13 = 11.8
calculate the pH for [H] 0.000251
-log(0.000251 = 3.6
calculate [H] for pH 3.12
10(-3.12 = 7.59x10-4
calculate [H] for pH 6.09
10(-6.09 = 8.13x10-7
calculate [H] for pH 12.01
10(-12.01 = 9.77x10-13
what is a high pH value in terms of ion concentration?
- 14
- low conc of H+ ions
what is a low pH value in terms of ion concentration?
- 0
- high conc of H+ ions
what is the strength of an acid?
the extent of its dissociation into H+ and A- ions when in aq solution
describe strong acids
- good proton donors
- dissociate completely
describe weak acids
- poor proton donors
- partially dissociate
(reversible arrow in equation)
where does equilibrium lie when a weak acid dissociates?
left
- only partially dissociates
where does equilibrium lie when a strong acid dissociates?
right
- fully dissociates
write the general equation for dissociation of a weak acid
HA <=> H+ + A-
state the general Ka expression
[H+] [A-] / [HA]
[products]/[reactants]
what does Ka show?
extent of acid dissociation
what does a large value of Ka show?
shift of equilibrium to the right
greater dissociation = greater acid strength
how is pKa calculated?
-logKa
what is pKa?
a way of measuring the strength of an acid similar to pH
what does a low pKa tell you?
stronger acid
