keywords:
Bookmark and Share



Front Back
Describe the fundamental behaviour of acids and bases and define the terms acids, bases and salts
Acids - proton doners
Bases - Proton acceptors
Salts - ionic compounds composed of metallic ions and non-metalic ions (NaCl)
Arrhenius' concept of acids and bases
Acids dissociate in water to produce hydrogen ions
Bases dissociate in water to produce hydroxide ions
Acid-base reactions in water form undissociated molecules of water
Only applies for aqueous solutions
Bronsted-Lowry's concept of acids and bases
An acid is a H+ ion or proton donor
When an acid loses a proton, its conjugate base is formed
HA + H2O --> H3O+ + A-

A base is a proton acceptor
When a base accepts a proton, its conjugate acid is formed
B + H2O --> BH+ + OH-
Acids and their conjugate bases
HCl --> Cl-
H2SO4 --> HSO4-
HNO3 --> NO3-
H3PO4 --> H2PO4-
H2O --> OH-
HCO3- --> CO32-
CH3COOH --> CH3COO-
NH3 --> NH2-
HCOOH --> HCOO-
Bases and their conjugate acids
H2O --> H3O+
HSO4 --> H2SO4
NO3- --> HNO3
HPO4- --> H2PO4
OH- --> H2O
CO3- --> HCO3
Explain the term amphiprotic species
An amphiprotic species can act both as an acid and a base in a reaction (e.g. water)
H20 + H2O --> H3O+ + OH-
What is strength of an acid/base?
Strength refers to the amount of dissociation which occurs in solution in water - denoted by the acid/base dissociation content (Ka/Kb)
A strong acid or base will undergo complete dissociation, these have a large Ka value
A weak acid or base will only have a small number of molecules dissociate into ions, these have a small Ka value
What is concentration of an acid/base?
Concentration is a measure of the amount of a given substance (solute) in a given volume of solution (usually M/L)
A substance can be dilute or concentrated.
It is possible for a weak substance to be concentrated or vice versa.
Define the term acid dissociation constant (Ka) and relate the acid dissociation constant to the strength of the acid
Acid dissociation constant is denoted by Ka. It is a quantitative measure of how strong or weak and acid is. For a hypothetical acid (HA), Ka can be found by:
HA + H2O --> H3O+ + A-
Ka = product/reactants
Define the terms pH and pOH
Calculate the pH and pOH of a solution of an acid or a base
pH = -log10[H+]

pOH = -log10[OH-]
Relate the pH of biological fluids to their acidic or basic nature
Gastric fluids have a pH of about 1 so they are able to break down our food. The cytoplasm of a cell has pH similar to water to ensure intra and  extracellular fluids are equivalent
Describe how an acid-base titration is carried out
An acid-base titration involves progressive addition of an acid or base solution in a burette to a given volume of an acid or base in a conical flask
The solution in the beaker should have an indicator of pH meter in it which will allow the investigator to determine the end point of the reaction
The concentration of the solution in the beaker must be known to allow the concentrtion of the solution in the burette to be determined (e.g the acid and base dissociation ratio can be found from the word equation, knowing this ratio allows determination of the concentration of the other solution)
Distinguish between the end point and the equivalence point
The end point is the point in which the titration is complete
The equivalence point is the point where the reactants have been added in equal proportions - shown by a change in pH
Define the terms: pKa, pKb and Kw
pKa = -log10(Ka)
pKb = -log10 (Kb)
Kw = [H+] [OH-]: water ionisation constant
Determine the pKa of a weak acid from its titration curve
pKa = pH at half titration point

To find pKa
1. Find the titration point
2. Half the titration point at x axis
3. Draw vertical line up at half titration point
4. Draw a horizontal line from h to the y axis
5. pKa = pH where horizontal line hits the y axis
Define and give examples of buffers
Buffers assist in the maintainance of homeostasis by resisting changes in pH that would otherwise result from the addition of a small amount og an acid, base or water (dilution).
Buffers usually consist of a mixture of weak acid and its conjugate base or a weak base and its conjugate acid.
Buffers can act as both a source and a sink for protons [H+]
(e.g. pH of the blood is carefully maintained within narrow limits of 7.4 by buffers such as H2CO3/HCO3-
Describe acidosis and alkinosis
Acidosis - an increase acidity of the blood, specifically when blood plasma falls below 7.35
Alkinosis - abnormally high alkalinity of the blood and other tissues (low H+ concentration)
Strong Acids
HCl - Hydrochloric Acid

H2SO4 - Sulfiric Acid

HClO4 - Perchloric Acid

Weak Acids
H2CO3 - Carbonic Acid

CH3COOH - Acetic Acid

HCN - Hydrogen Cyanide
Strong Bases
NaOH - Sodium Hydroxide

KOH - Potassium Hydroxide

Ba(OH)2 - Barium Hydroxide
Weak Bases
NH3 - Ammonia

CH3NH2 - Methylamine
x of y cards