Chromatography and gas tests Flashcards
What is a pure substance
It is a single element or compound which isn’t mixed with any other substance,
State properties of pure substances
Pure substances melt and boil at specific temperatures, heating graphs can be used to distinguish pure substances from impure.
Melting point of a pure substance has straight lines on graph
Melting point of an impure substance has curvy lines on graph
What is a formulation
It is a mixture that has been designed as a useful product
How are formulations made
By mixing chemicals that have a particular purpose in carefully designed quantities.
State examples of formulations
Fuels, cleaning agents, paints, medicines and fertilisers.
What is chromatography?
It can be used to separate mixtures and help identify substances
What does chromatography involve?
A mobile phrase (e.g water or éthanol) and a stationary phase (e.g chromatography paper)
What are Rf values
The ratio of the distance moved by a compound to the distance moved by the solvent
How are Rf values calculated?
Distance moved by substance / distance moved by solvent (mobile phase, water)
How are pure substances distinguished in comparison to impure substances on chromatography paper?
Pure substances will produce a single spot in all solvents whereas an impure substance produces multiple spots.
State 5 ways to separate mixtures
Chromatography
Filtration
Crystallisation (evaporation)
Distillation
Fractional distillation
In paint, what is known by the terms ‘binder’ ‘solvent’ and ‘pigment’
Binder - helps the paint attach itself to an object
Solvent - helps the binder and pigment spread by thinning them out
Pigment - to provide colour.
In cleaning fragrances, what is meant by the terms ‘water’ ‘surfactant’ ‘colouring / fragrance’ and ‘rinse agent’ ?
Water - thins out the mixture so it can be sprayed easier from the bottle
Surfactant - the actual detergent that helps the remove stains or grease
Colouring / fragrance - improves appeal to customers
Rinse agent- helps water drain off crockery.
What can chromatography help detect?
Drugs, explosives, dyes and paints
The resulting pattern of colour in chromatography is called…
A chromatogram
State the 7 steps to chromatography
1- draw a pencil line on a piece of chromatography paper
2- pour some water into beaker
3-stand paper in beaker (water must be below pencil line)
4-spot the mixture needed to be separated
5- let the spot dry
6- leave until water has almost reached top of paper
7- remove the paper and hang chromatogram up to dry
What do we refer an unknown as in chromatography?
U
What is a stationary and mobile phase?
Stationary - isn’t moving
Mobile- moving
What is an unknown substance?
A substance nor shared between multiple in common substances.
How can a substance be identified on a database?
The Rf of an unknown substance is compared with values of other substances on an online database.
What is a solvent front?
The point where the solvent stops moving
What does soluble mean?
Ability to be dissolved
What does solution mean?
A homogenous mixture of two or more substances
What is a solute?
A solid, liquid or gas which is dissolved to make a solution
