C6 CHEMICAL ANALYSIS Flashcards
pure substance?
consists only of one element or one compound
how do you determine if a substance is pure?
measure its boiling and melting point
when does a pure substance melt?
at a specific fixed temperature
when does a pure substance boil?
at a specific fixed boiling point
when does an impure substance melt or boil?
over a range of temperatures
what is a formulation?
complex mixture that has been designed as a useful product.
in a formulation , the quantity of each component is carefully measured so that the product has the properties we need.
examples of formulation?
fuels , cleaning products , paints , medicines, alloys , fertilisers and food
what does paper chromatography allow us to do?
separate substances based on their different solubilitys
what does paper chromatography allow us to do?
separate substances based on their different solubilitys
explain paper chromatography
draw a pencil line near the bottom on the chromatography paper.
we put a dot of our first colour onto the pencil line next to that we put our second colour onto the pencil line (we can use many colours as long as we have space on the pencil line)
place the bottom into the solvent (liquid which dissolves substances)
solvent moves up the paper, it dissolves the ink and the two coloured dots , these are carried up the paper as well
stationary phase in paper chromatography?
the paper does not move
stationary phase in paper chromatography?
the paper does not move
mobile phase in paper chromatography?
the solvent does move
mobile phase in paper chromatography?
the solvent does move
how do you know if we have a pure compound on the paper?
it will produce a single spots in all solvents
how do you know if we have a pure compound on the paper?
it will produce a single spots in all solvents
how do you know if we have a mixture on the paper?
may separate into different spots depending on the solvent
how do you know if we have a mixture on the paper?
may separate into different spots depending on the solvent
how do you know if we have a mixture on the paper?
may separate into different spots depending on the solvent
how do you know if we have a mixture on the paper?
may separate into different spots depending on the solvent
why does paper chromatography work?
because different substances have got different solubilities
more soluble substance travels further up the paper then a substance which is less soluble
why does paper chromatography work?
because different substances have got different solubilities
more soluble substance travels further up the paper then a substance which is less soluble
why do we draw our starting line in pencil in chromatography?
if we drew the line in pen , the pen ink would move up the paper with the solvent
why do we draw our starting line in pencil in chromatography?
if we drew the line in pen , the pen ink would move up the paper with the solvent
problems with chromatography?
several different substances could have the same Rf value. We might need to repeat this experiment using a different solvent
if this substance has never been analysed before, then there will not be an Rf value on the database
test for hydrogen?
remove the bung and insert a burning splint, hydrogen gas burns rapidly and produces a pop sound
test for oxygen?
insert a glowing splint into the test tube of oxygen, the splint relights (bursts into flames)
test for carbon dioxide?
use lime water ( aqueous solution of calcium hydroxide.
draw some of the gas into a plastic pipette.
bubble the gas through the lime water, if we repeat this, the lime water may turn cloudy = carbon dioxide
test for chlorine?
insert damp litmus paper into the mouth of the test tube, chlorine bleaches litmus paper white
