Researching Chemistry pt 1 ✓ Flashcards
Volumetric analysis
What is Titration?
Titration is the accurate measurement of the volume of the standard to determine the concentration of the analyte
What is a Standard solution?
A standard solution is a solution of accurately known concentration
What is an Analyte?
An analyte is a solution of an unknown concentration
What is an Indicator?
Give two examples -
An indicator is a substance that is used to determine the end point of a reaction
(Phenolphthalien, Methyl orange)
What are Concordant results?
Concordant results are results within 0.2cm3
What must a Primary standard have? (4)
Give two examples -
A primary standard must have a:
- High state of purity
- Be stable when solid and in solution
- Be soluble
- Have a reasonabley high GFM
(Sodium carbonate, Hydrated oxalic acid)
When can’t compounds be used as a Primary standard? (3)
Give an example -
When they have a low GFM, are unstable as a solid or in solution, or absorb moisture from the air
(Sodium hydroxide, NaOH)
What is a Secondary standard?
A secondary standard is a standard that is prepared by titrating it against a primary standard
What is a Complexometric titration?
A complexometric titration is used to determine the concentration of metal ions in a solution
How is a Complex formed?
Give an example of a ligand -
A complex is formed when a metal ion reacts with a ligand (EDTA)
What is a Ligand?
A ligand is a molecule/negative ion with at least one non-bonding pairs of electrons that they donate to unfilled metal orbitals to form dative bonds
What is a Dative bond?
A dative bond is a covalent bond where one atom supplies both of the electrons
What is EDTA?
EDTA is a commonly used ligand. It wraps around the metal using 6 dative bonds (hexadentate). It is used to treat heavy metal poisoning or remove a metal from water
What is an Metal ion indicator?
Give an example -
A metal ion indicator is an organic dye that changes colour when it binds to metal ions
(Murexide (ln))
What is Back titration?
A back titration is a titration where a known quantity of one standard is added in excess to a known mass of analyte. Once the reaction is complete, the excess of the standard is determined by titration against a second standard
When is Back titration used? (3)
- When the analyte is insoluble/has low solubility
- When the end-point is clearer for back titration than direct titration
- If the reaction is slow between the standard and analyte
