Acids, Bases and pH Flashcards
What is an alkali
a soluble base
What is a bronsted-lowry acid
a proton donor
What is a bronsted-lowry base
a proton acceptor
What is a conjugate acid base pair
contains 2 species that can be interconverted by transfer of a proton
What is a monobasic acid
there is 1 hydrogen ion in the acid that can be replaced per molecule in an acid-base reaction
What is a dibasic acid
there are 2 hydrogen ions in the acid that can be replaced per molecule in an acid-base reaction
What is a tribasic acid
there are 3 hydrogen ions in the acid that can be replaced per molecule in an acid-base reaction
What is pH
-log[H+(aq)]
How to work out H+ concentration from pH
10^-pH
A change of 1 pH number is equal to how many times difference
x10
What is a strong acid
completely dissociates in aqueous solution
What is a weak acid
partially dissociates in aqueous solution
What is Ka
the acid dissociation constant used for acid base equilibria
What is the Ka formula
[H+][A-] /[HA]
What can cause Ka to change
Temperature
What does a large Ka mean
Further equilibrium is to the right. The greater the disassociation/strength of acid
How do you convert Ka to pka
-log(ka)
How do you convert pka to ka
10^-pka
What is the purpose of pka
makes values more manageable than ka and it is much easier to compare relative acid strengths using pka
The stronger the acid…
larger the ka and the smaller the pka
the weaker the acid…
the smaller the ka and the larger the pka
What does [H+] depend upon
concentration of acid and the acid dissociation constant
What approximations are made when calculating pH of acids
- HA dissociates to produce equilibrium concentrations of H+ and A- that are equal.
- the equilibrium concentration of HA is smaller than the undissociated concentration.
How can Ka be calculate used equilibrium concentrations
[H+]eqm[A-]eqm/[HA]eqm or [H+]2/[HA]
How to solve pH of a weak acid using Ka
[H+] = square root of (Ka x [HA])
What can the ka of a weak acid be determined by
preparing a standard solution of a weak acid of a known concentration. Measuring the pH of the standard solution using a pH meter.
What approximations are made involving weak acids
- Assumes that the dissociation of water is negligible.
2. The concentration of acid is much greater than the H+ concentration at equilibrium.
What is kw
the ionic product of water
What is the kw formula
[H+][OH-] = 1x10-14
What is the importance of kw
controls the concentrations of H+ and OH- in aqueous solutions
How do you calculate H+ and OH- concentrations in aqueous solution when given pH
- 10^-pH = [H+]
2. Kw/[H+] = [OH-]
What is a strong base
an alkali that completely dissociates in solution
What is a monoacidic base
each mole of a base releases one mole of OH-(aq) ions e.g.NaOH
How do you calculate the pH of a solution of a strong base
- concentration of base = [OH-]
- kw/[OH-] = [H+]
- -log[H+] = pH
What is a weak base
partially dissociates in solution so one mole of a base releases far less than one mole of [OH-]. e.g.NH3
How do you find pka form a titration curve
Find volume needed to reach the end point (steep part of the curve). Divide the volume by 2 and use your graph to find the pH. pka=pH
