Practical skills and techniques Flashcards
What is the most accurate way the measure the mass of reactants and products?
By weighing by difference
What are desiccators used to store?
Samples in a dry atmosphere
What does vacuum filtration involve?
Carrying out a filtration under reduced pressure and provides a faster means of separating a precipitate from a filtrate
What can be used during vacuum filtration?
A Buchner, Hirsch or sintered glass funnel
What does heating under reflux allow?
Heat energy to be applied to a chemical reaction mixture over an extended period of time without volatile substances escaping.
When carrying out heating under reflux where is the reaction mixture placed?
In a round-bottomed flask with anti-bumping granules and the flask is fitted with a condenser then it is heated.
What is distillation?
A technique used to purify and identify organic compounds
What can distillation be used to do?
Purify a compound by separating it from less volatile substances in the mixture.
What does solvent extraction involve?
Isolating a solute from a liquid mixture or solution by extraction using an immiscible solvent in which the solute is soluble. The quantity of solute extracted is greater using a number of extractions with smaller volumes of solvent than a single extraction using a large volume of solvent.
The technique of recrystallisation is used to?
Purify an impure solid.
The solvent for recrystallisation is chosen so that the compound being purified is?
Completely soluble at high temperatures and only sparingly soluble at lower temperatures
A pure compound can be identified by?
Melting point analysis with reference to literature melting point value.
Determination of the melting point of a compound can give an identification of the?
Purity of a compound. Presence of impurities in the compound lowers the melting point and broadens its melting temperature range due to the disruption in intermolecular bonding in the crystal lattice.
What does determination of a mixed melting point involve?
Mixing a quantity of the product with the pure compound and determining the melting point range.
The melting point value and the range of the melting temperature is used to determine?
Whether the product and the pure compound are the same substance
