Researching Chemistry Flashcards
What is recrystallisation?
A process used to purify solids
What is an example of something that can be purified by recrystallisation?
Aspirin
What are the required qualities for the solvent in a recrystallisation reaction ?
The solid must have a low solubility in the solvent at room temp or below but be readily soluble in the solvent at higher temperatures
What is mixed melting point analysis ?
A process used to identify if a product is pure or not
What is vacuum filtration ?
A filtration under reduced pressure that uses a Büchner funnel (lined with filter paper) and a vacuum flask.
What is refluxing ?
A technique which allows substances to be heated for long periods of time without volition substances escaping
What are essential to preventing accidents in refluxing?
Anti-bumping granules
What is distillation ?
A process used to purify a liquid compound by heating away its impurities
Which end does the water go IN in a reflux reaction ?
The bottom
Which end does water do IN in a distillation reaction ?
At the top
What can distillation be used for (besides separation) ?
Identifying compounds - but their boiling point
What is solvent extraction ?
The process used to remove crude product from the reaction mixture
How much crude product is left in the separation funnel after each solvent extraction ?
30%
How does solvent extraction work ?
The crude product must be more soluble in the chosen solvent than in the reaction mixture. The solvent has to be immiscible in the reaction mixture thus creating two distinct layers. The layers are separated using a separation funnel
What is gravimetric analysis?
A method of analysis for finding the mass of an element or substance in a compound.
How does a gravimetric analysis experiment work ?
A substance of an unknown composition is forced to form a solid substance of known composition. It uses precipitation
What are the essential qualities of a product of gravimetric analysis ?
A low solubility
A large particle size
Be a stable compound at temps between 100-110C
What are back titrations used for ?
Finding the number of moles of a substance by reacting it with excess of a reactant of known concentration.
This mixture is then titrated to work out the number of moles used in the first reaction.
When are titrations useful ?
When trying to work out the quantity of a substance with a low solubility
What are Complexometric Titrations ?
Often to determine the concentration of metal ions present in a solution
How do complexometric titrations work ?
Complexes are formed.
EDTA is often used - a ligand that binds in a 1:1 ratio with most metal ions
What is a desiccator?
Sealed glass container used in gravimetric analysis
