experimental chemistry Flashcards
methods for collecting gases + when to use them + egs
- water displacement: for gases NOT soluble in water. example : hydrogen
- upwards delivery: for gases less dense than air. example ammonia.
- downwards delivery: for gases more dense than air . example: chlorine
methods for drying gases + what are they not suitable for + examples of gases we can dry
- concentrated sulfuric acid : can be used for hydrogen chloride and chlorine
- quicklime (calcium oxide) : can be used for ammonia
- fused calcium chloride : can be used for hydrogen, nitrogen and carbon dioxide
- don’t use any gases that react with the gages you need to dry
why do we need to dry gases
remove moisture and impurities
methods to separate solid-solid mixtures
- magnetism
- sieving
- using suitable solvents (followed by evaporation to dryness)
- sublimation
methods to separate solid-liquid mixtures
- evaporation to dryness
- crystallisation
- simple distillation
methods to separate liquid-liquid mixtures
- fractional distillation
- separating funnel (heterogeneous mixtures)
- paper chromatography
how to calculate R.F. value
distance travelled by substance / distance travelled by solvent
how can purity of substances be determined?
higher bp, lower mp
magnetism
separate magnetic substances from non magnetic substances
sublimation
used to separate a substance that changes from solid to gaseous state directly
filtration
used to separate insoluble solids from liquids
evaporation to dryness
to separate a dissolved solute from a solvent by heating the solvent until all the solute has vapourised
crystallisation
used to obtain a pure solid from its saturated solution
simple distillation
used to obtain a pure solvent from a solution
separating funnel:
used to separate immiscible liquids
paper chromatography :
used to separate a mixture of substances which have different solubilities in a given solvent
fractional distillation
used to separate miscible liquids with different boiling points
what to do to identify colourless substances on chromatogram?
spray locating agent
