Acids and Bases Flashcards
(22 cards)
strong acid
- donates high percentage of its protons to water.
- low pKa
equivalence point
Point in a titration when sufficiently solution has been added to react exactly with the substance in solution in the flask.
Are phenols or benzene rings stronger acids?
Phenols
Electron donating groups on phenol _____ acid strength
reduces
weak monoprotic acid.
Monoprotic: can donate only one proton (H+) to water.
Weak: donates very low % of protons of O-H group to water.
Ka
Ka is the acid dissociation constant.
For an acid HA: Ka = [H3O+(aq)][A(aq)]/[HA(aq)]
amphiprotic species
- a species which can act as both a proton donor (acid) and a proton acceptor (base). For example: HCO3-
diprotic acid
can donate (up to) two protons (H+) to water.
Explain why HO2CCH2CO2 is a weaker acid than HO2CCH2CO2H
HO2CCH2CO2 as a charged species loses a proton less readily
than HO2CCH2CO2H.
triprotic acid
can donate (up to) three protons (H+) to water. An example is phosphoric acid, H3PO4.
pKa
pKa = -log10Ka, where Ka is the acid dissociation constant. For an acid HA: Ka = [H3O+(aq)][A(aq)]/[HA(aq)]
autoprotolysis
The term relates to the equilibrium constant (Kw)for D2O reacting with itself as shown in (i) above. Kw = [D3O+][OD]
conjugate base
- the species remaining after a Brønsted acid has transferred a proton is the conjugate base. Cl is the conjugate base of HCl.
autoprotolysis constant
- (of water, Kw) is defined by Kw = [H3O+][OH]
equivalence point
The point in a titration where the exact amount of titrant has been added to react with all the compound being analysed. e.g. In the determination of ethanoic acid in vinegar the point at which the amount of base added has converted all the ethanoic acid to ethanoate.
Explain why the hydrogen citrate ion (formed on loss of two protons from citric acid) is a weaker acid than citric acid.
Removing the third proton from citric acid (that is from the hydrogen citrate ion) gives a conjugate base with a higher negative charge. H+ more difficult to remove. weaker acid
electrophoresis
Electrophoresis is the separation of mixtures of amino acids based on their different isoelectric points.
zwitterion
- overall neutral species formed by internal proton transfer. For example: +H3NCH2CO2−
indicator
An indicator is a weak acid whose acid and conjugate base have different colours. For example: phenolphthalein
acid rain
Rain with pH
isoelectric point
The pH at which the majority species in solution is the zwitterion.
For example: glycine at pH 5.97 is mostly +H3NCH2CO2−
What is meant by the term ‘buffer capacity’?
Ability to resist change in pH on addition of acid or base.
