Chemical analysis Flashcards
(29 cards)
what is a pure substance?
contains only one type of compound or element
why is purity important?
only pure substances melt and boil and a specific temp
what is a formulation?
a mixture that has been designed as a useful product.
how are formulations made?
by mixing the components in carefully measured quantities to ensure that the product has required properties
what are some examples of formulations?
fuels, cleaning agents, medicine, fertilisers and food and alloys
if we test a substance for purity by measuring its boiling point, is that a physical test or a chemical test?
physical.
what is the mobile phase?
where the molecules can move (solvent)
what is the stationary phase?
molecules can’t move (paper)
what will happen if none of the substances are soluble?
the ink won’t move
what are the spots left behind in chromatography?
chromotogram.
how do you calculate the rF value?
distance travelled by substance/ distance travelled by solvent.
how do you spot a pure substance in chromatography?
it wont separate so there will only be one dot and only one rF value.
what is chromatography used for?
to separate a mixture of soluble substances in liquids.
what colour does a flame turn in the presence of calcium ions?
orange-red
what colour does a flame turn in the presence of copper ions?
green
what colour does a flame turn in the presence of lithium ions?
crimson
what colour does a flame turn in the presence of potassium ions?
lilac
what colour does a flame turn in the presence of sodium ions?
yellow
how do you do a flame test?
light a bunsen burner and open air hole for blue flame. pick up small sample of solid salt on a clean loop wire. hold the sample in the edge of the flame. observe and record flame colour. wash loop with dilute hydrochloric acid before continuing with other flame tests.
what is the method to test for metal cations?
dissolve a little solid salt in a test tube using distilled water. add a few drops of dilute NaOH solution drop wise. record any precipitate formed.
what’s the method for testing for ammonium ions?
dissolve a little solid salt in a test tube using distilled water. add dilute NaOH solution and heat gently. remove the flame and hold a piece of damp red litmus paper near mouth of test tube. record any changes in colour.
what is the method for testing for carbonate ions?
put little solid salt in a test tube and add a few drops of dilute acid. record of any bubbling occurs. use limewater to check that any bubbles contain limewater.
what is the method for testing for aulfate ions?
dissolving a little solid salt in a test tube using distilled water. add a few drops of dilute hydrochloric acid, and then add a few drops of chloride solution. record if a white precipitate forms.
what is the method for testing for halide ions?
dissolve a little solid salt in a test tube using distilled water. add a few drops of silver nitrate solution. record the colour of any precipitate formed.
