C8 Flashcards
what is a pure substance?
something that only contains one compounds or elements through out- not mixed with anything else.
how does the boiling point of a substance tell you if it’s pure or not?
chemically pure substances will melt or boil at a specific temperature
what are formulations?
mixtures with the exact amount of components made for a precise purpose.
what are the two ‘phases’ of chromatography?
stationary phase-where its not moving (solid or thick liquid)
mobile phase-where molecules can move (always liquid or gas)
how quickly a chemical moves through chromatography depends on what?
its distribution between the two phases-weather it spends more time in the mobile stage or stationary phase as it constantly switches between both.
what pattern will a pure substance produce in chromatography?
it will only produce one dot/spot as there’s only one substance to sample
during paper chromatography what is the stationary and mobile phase?
stationary phase- filter paper
mobile phase- solvent (e.g ethanol or water)
what is the Rf value of a chemical?
the ratio between the distance travelled by the dissolved substance (the solute) and the distance travelled by the solvent (water).
what can you use to calculate the Rf value
Rf = distance moved by the compound ÷ distance moved by the solvent
what are the four gases that tests are done on?
-chlorine -oxygen -carbondioxide -hydrogen
describe the test for chlorine
litmus paper is placed in solution. if chlorine is present it bleaches the paper white (may turn red at first because a solution of chlorine is acidic)
whats done to test for oxygen?
put a glowing splint inside a test tube. if oxygen is present, the glowing splint will re-light.
what’s done to test for carbon dioxide?
shake the aquas solution of calcium hydroxide (known as limewater) if it turns cloudy then carbon dioxide is present.
what is done to test for hydrogen?
hold a lit splint at the end of the open end of a test-tube. if hydrogen is present, you will get a squeaky pop-the noise comes from the hydrogen burning quickly with the oxygen in the air to from H2O.
