C2.1 Flashcards
empirical formula
simplest whole number ratio of atoms of each element in a compound e.g C6H6= CH
describe a pure element
a pure element or compound contains only one substance
describe an impure element or compound
impure materials may be composed of a mixture of elements, compounds or both
filtration
separates an insoluble solid from a liquid
soluble
substance that can dissolve
insolube
substance that can’t dissolve
crystillisation
used to separate a soluble solid from a liquid
chromatography
used to separate mixtures
stationary phase
the paper
mobile phase
the solvent
establishing purity
-purity of an element can be established by it’s melting point
-impure compounds have a large range of melting points
-pure compounds have a definite melting and boiling point
solute
soluble solid
solvent
liquid
solute + solvent –>
solute + solvent –> solution
why does distillation work?
distillation works because parts of the mixture have different boiling points, the mixture is heated and the substance with the lowest boiling point evaporates first, it enters the condenser where it’s cooled, condensed and collected
fractional distillation
-used to separate a mixture of two or more misicrite liquids
-fractioning column improves separation as it has a high surface area
how does chromatography work?
each substance travels at a different rate, depending on their relative attractions to each phase
why do we draw the start line in pencil for chromatography?
if we drew it in pen it would bleed into the other colours
why should the water be below the start line in chromatography?
the water would touch the dyes and dissolve them of the paper
how do we calculate RF value?
distance travelled by substance / distance travelled by solvent
thin layer chromatography
more accurate from of chromatography and uses an inert layer for the stationary phase
