Unit 3-Volumetric Analysis Flashcards
What is a standard solution?
A solution of accurately known concentration.
Describe how a standard solution would be made from a primary standard.
- Accurately measure out required mass of primary standard
- Dissolve in a small volume of solvent.
- Transfer solution and rinsings into volumetric flask
- Make up to graduation mark
- Stopper and invert to mix
What are 4 characteristics of a primary standard?
be available in high state of purity
be stable when solid and in solution
be soluble
have a reasonably high GFM
Which of the following chemicals would not be suitable as a primary standard?
Sodium carbonate (Na2CO3)
Sodium hydroxide (NaOH)
Hydrated oxalic acid (H2C2O4.2H2O)
Explain your answer
Sodium hydroxide has a relatively low GFM, is unstable as a solid (absorbs moisture), unstable as a solution.
What must be carried out before using sodium hydroxide in a volumetric analysis?
Standardisation
How would a solution of sodium hydroxide be standardised?
Titrate with standard solution/solution of known
concentration of a suitable chemical.
For example use oxalic acid for standardising sodium hydroxide or potassium permanganate.
What are the four different types of volumetric analysis?
Acid/base titrations
Redox titrations
Complexometric titrations
Back titrations
Give an example of the following types of titrations
- Acid/base titrations
- Redox titrations
- Complexometric titrations
- Back titrations
Acid/base titrations-Sodium hydroxide and hydrochloric acid or any non weak/weak pairing.
Redox titrations-Oxalic acid and potassium permanganate or any example based on reactions between oxidising and reducing agents.
Complexometric titrations-based on reactions in which complexes are formed — EDTA and metal ions
Back titrations-useful for solid substances with low solubility calcium carbonate.
