Gravimetric & Volumetric Analysis (U3, c1 and 2 /4) Flashcards
What is “weighing by difference” in Gravimetric Analysis?
Finding the final mass of the substance by subtracting {mass of crucible} from {mass of crucible + the dried substance}.
What is “heating to constant mass” in Gravimetric Analysis?
Heating the substance, allowing it to cool in a desiccator (dry atmosphere) and then reweighing it in a crucible, until there is no mass change between consecutive measurements.
What is Gravimetric Analysis?
Gravimetric Analysis is a quantitative determination of an analyte based on the mass of a solid.
What is a standard solution?
One of which the concentration is known accurately and can be prepared from a primary standard.
What are the FOUR characteristics that a primary standard must have?
> A high state of purity
Stability in air and water
Solubility
Reasonably high formula mass
State the SIX steps in preparing a primary solution!
- Calculate the mass of the primary standard required.
- Weigh out the primary standard as accurately as possible.
- Dissolve the primary standard in a small vol. of water in a beaker.
- Transfer the solution and rinsings into a standard flask.
- Make it up to the mark with deionised water.
- Invert the stoppered flask several times.
What is standardisation?
The process of determining the exact concentration of a solution.
What does the use of a control in a chemical reaction do?
It validates the technique.
What happens in complexometric titration?
The formation of a coloured complex is used to indicate the end point of a titration.
Give an example of a complexometric reagent. What kind of ligand is it?
EDTA is a complexometric reagent, and a hexadentate ligand.
What is a back titration used for? How can this be done?
For finding the number of moles of a substance by:
- Reacting it with an excess volume of reactant of known concentration, and then
- The resulting mixture being titrated to work out the number of moles of the reactant in excess.
What kind of substance is a back titration useful for in particular?
An insoluble solid.
