Reactivity 3.1 (HL) Flashcards
(22 cards)
Is the dissociation of water into its ions an endo or exo process?
Endothermic
Dissociation of water
H2O -> H+ + OH-
What happens to Kw when temperature increases?
Kw increases as equilibrium shifts to the product side.
Ka for weak acids (dissociation/ionisation)
Weak acids slightly dissociate to their ions.
What happens to weak bases when in aqeous solution?
Weak bases are slightly ionised by accepting a proton in aqueous solution
pH + pOH =
14
The weaker the acid…
the smaller the Ka and the higher the pKa
Ka x Kb =
Kw
pKa + pKb =
14
Strong acid and strong bases forming salts
Strong acid and base cancel out to create a neutral solution of salts with a pH of 7
Weak acid and strong bases forming salts
Create a basic solution of salts with a pH>7
Weak acid and weak bases forming salts
Tend to be neutral as cancel out
Acid base indicators
Weak acids or weak bases where the colours of the components of the conjugate acid-base pairs are different
Where do indicators change colour?
Within +/- 1 pH unit of their pKa or pKb values
What does a buffer solution do?
Resists a change in pH when small amounts of acid or base are added
How are acidic buffer solutions created?
Weak acid and the salt formed from the weak acid and a strong base
How can acidic buffer solutions be prepared?
Dissolving the salt in a solution of the weak acid or reacting a solution of the strong base with an excess of weak acid
Where are the most efficient buffers formed?
Half equivalence point
How are alkaline buffer solutions created?
Weak base and salt formed from the weak base and strong acid
How can alkaline buffer solutions be prepared?
By dissolving the salt in a solution of weak base or reacting a solution of strong acid with excess of weak base
How to work out pH of acidic buffer?
pH = pKa + log (conjugate base/weak acid conc)
How to work out pOH of basic buffer?
pOH = pKb + log (conjugate acid/weak base conc)
