Glossary: Acid Definitions
Acid A proton donor - releases H+.
Acidic A buffer with a pH less than 7 - weak acid which is present alongside its
Buffer (conjugate base) salt to counteract changes in pH.
Base A proton acceptor - accepts H+.
Basic Buffer A buffer with a pH more than 7 - weak base which is present alongside its
(conjugate acid) to counteract changes in pH.
Buffer Resists changes in pH when small amounts of acid/alkali are added.
End Point The point during the titration when the indicator changes colour. A suitable
indicator should change colour near the equivalence point (so should have a
pH range within the pH change during the equivalence point).
Equivalence The point when full neutralisation occurs. When titrating an acid with a base, it
Point is the point when all acid has been neutralised, and so [H+ ]=[OH− ].
Indicator Indicators are chemical solutions which will change colour when there is a
change of pH. Methyl orange and phenolphthalein are indicators commonly
used in titrations. Methyl orange is red in an acid and changes to yellow in an
alkali. Phenolphthalein is colourless in an acid and changes to pink in an alkali.
Ka Ka = [H+] [A-]/[HA]
An acid disassociation constant.
A larger Ka means a stronger acid.
Kw Kw = [H+] [OH-]
Ionic product of water.
Monoprotic An acid which releases one H+ ion for each molecule present.
Diprotic A acid which releases two H+ ions for each molecule present.
Neutralisati A reaction between an acid and a base which react together to form water and
on a salt. The ionic equation for neutralisation:
H+ + OH- <=> H2O
pH -log10[H+]
Acid A proton donor - releases H+.
Acidic A buffer with a pH less than 7 - weak acid which is present alongside its
Buffer (conjugate base) salt to counteract changes in pH.
Base A proton acceptor - accepts H+.
Basic Buffer A buffer with a pH more than 7 - weak base which is present alongside its
(conjugate acid) to counteract changes in pH.
Buffer Resists changes in pH when small amounts of acid/alkali are added.
End Point The point during the titration when the indicator changes colour. A suitable
indicator should change colour near the equivalence point (so should have a
pH range within the pH change during the equivalence point).
Equivalence The point when full neutralisation occurs. When titrating an acid with a base, it
Point is the point when all acid has been neutralised, and so [H+ ]=[OH− ].
Indicator Indicators are chemical solutions which will change colour when there is a
change of pH. Methyl orange and phenolphthalein are indicators commonly
used in titrations. Methyl orange is red in an acid and changes to yellow in an
alkali. Phenolphthalein is colourless in an acid and changes to pink in an alkali.
Ka Ka = [H+] [A-]/[HA]
An acid disassociation constant.
A larger Ka means a stronger acid.
Kw Kw = [H+] [OH-]
Ionic product of water.
Monoprotic An acid which releases one H+ ion for each molecule present.
Diprotic A acid which releases two H+ ions for each molecule present.
Neutralisati A reaction between an acid and a base which react together to form water and
on a salt. The ionic equation for neutralisation:
H+ + OH- <=> H2O
pH -log10[H+]
