4.5 volumetric analysis

Question 1

preparing standard solution

Answer 1

• weighing a primary standard accurately
• dissolving in a small volume of solvent (usually deionised or distilled water) in a beaker
• transferring the solution and rinsings into a volumetric flask
• making up to the graduation mark with solvent
• stoppering and inverting
• Standard solutions can also be prepared by accurate dilution by pipetting an appropriate volume of a standard solution into a volumetric flask, making up to the graduation mark with solvent, stoppering and inverting

Question 2

• weighing a primary standard accurately
• dissolving in a small volume of solvent (usually deionised or distilled water) in a beaker
• transferring the solution and rinsings into a volumetric flask
• making up to the graduation mark with solvent
• stoppering and inverting
• Standard solutions can also be prepared by accurate dilution by pipetting an appropriate volume of a standard solution into a volumetric flask, making up to the graduation mark with solvent, stoppering and inverting

Answer 2

preparing standard solution

Question 3

standard solution

Answer 3

a solution of accurately known concentration is known as a standard solution

Question 4

a solution of accurately known concentration is known as a standard solution

Answer 4

standard solution

Question 5

primary standard requirements

Answer 5

• be available in a high state of purity
• be stable when solid and in solution
• be soluble
• have a reasonably high GFM

Question 6

• be available in a high state of purity
• be stable when solid and in solution
• be soluble
• have a reasonably high GFM

Answer 6

primary standard requirements

Question 7

examples of primary standards

Answer 7

• sodium carbonate
• hydrated oxalic acid
• potassium hydrogen phthalate
• silver nitrate
• potassium iodate
• potassium dichromate

Question 8

sodium hydroxide as a primary standard

Answer 8

• Sodium hydroxide is not a primary standard as it has a relatively low GFM is unstable as a solid (absorbs moisture) and unstable as a solution
• Sodium hydroxide solution must be standardised before being used in volumetric analysis

Question 9

examples of volumetric analysis

Answer 9

• acid-base titrations
• redox titrations based on reactions between oxidising and reducing agents
• complexometric titrations based on reactions in which complexes are formed — EDTA is an important complexometric reagent and can be used to determine the concentration of metal ions in solution
• back titrations used to find the number of moles of a substance by reacting it with an excess volume of a reactant of known concentration. The resulting mixture is then titrated to work out the number of moles of the reactant in excess. From the initial number of moles of that reactant, the number of moles used in the reaction can be determined. The initial number of moles of the substance being analysed can then be calculated. A back titration is useful when trying to work out the quantity of substance in a solid with a low solubility

Question 10

• acid-base titrations
• redox titrations based on reactions between oxidising and reducing agents
• complexometric titrations based on reactions in which complexes are formed — EDTA is an important complexometric reagent and can be used to determine the concentration of metal ions in solution
• back titrations used to find the number of moles of a substance by reacting it with an excess volume of a reactant of known concentration. The resulting mixture is then titrated to work out the number of moles of the reactant in excess. From the initial number of moles of that reactant, the number of moles used in the reaction can be determined. The initial number of moles of the substance being analysed can then be calculated. A back titration is useful when trying to work out the quantity of substance in a solid with a low solubility

Answer 10

volumetric analysis