C12 Flashcards
what is a pure substance
made up of one just one substance that can be an element or a compound
how is the test for water and pure water different
the test for water is that it turns white anhydrous copper sulfate blue but with pure water the test is that the melting point is exactly 0 degrees and the boiling point exactly 100
what is a formulation
a mixture that has been designed to give a product the properties to make it most effective at carrying out its function eg with medicinal drugs they often only contain about 5% of the active drug that affects the body to cure illness but they also contain colourants, sweetants, smooth coatings and other compunds to aid their dissolving at the most effective part of the digestive tract
paint is a common formualtion. what does it contain?
pigment to provide colour
binder so paint can attach itself to an object and form a protective film when dry
solvent to help pigment and binder spread well by thinning them out
what is chromatography used for
to separate and identify mixtures of soluble substances
how do chromatography results distinguish between pure and impure substances
pure produces one spot
impure produces 2 or more spots
how do you work out Rf values
distance travelled by substance / distance by solvent
what are Rf values used for
to identify unknown substances by referring them to databases with known substanes Rf values
what is the mobile and stationary phase in paper chromatography
mobile phase - chosen solvent
stationary phase - paper
how can you tell whether a substance has a stronger force of attraction to the mobile phase or the stationary phase
a stronger force of attraction to the mobile phase will be carried a greater distance in a given time but a stronger attraction to the stationary phase will not travle as far int the given time
what do you have to ensure to make the comparisons between Rf values valid
the solvent and the temperature used are the same as the ones quoted in the database
what is the test for hydrogen
hold a lighted splint over an open test tube of hydrogen gas and the lighted splint should ‘pop’
what is the test for oxygen
a glowing splint will relight
what is the test for carbon dioxide
limewater turns milky
what is the test for chlorine
damp blue litmus paper is bleached white
what are the flame colours that match with each metal ion
lithium- crimson sodium- yellow potassium- lilac calcium- orange red copper - green
what is the method for carrying out a flame test
1) nichrome wire loop is dipped in concentrated hcl and then heated to clean it. then dip in acid again
2) dip wire into metal compound being tested and hold loop in blue flame
3) flame should change colour and allow you to identify the metal ion
(sometimes if the metal is a mixture then the flame colour could be masked eg intense yellow colour of sodium ions can mask the others)
what can you tell if you react something with sodium hydroxide and a white precipitate forms
it is either aluminium, calcium or magnesium
what happens to precipitate formed by aluminium ions when excess sodium hydroxide is added
it dissolves however calcium and magnesium precipitates wont dissolve
how can you differentiate between calcium and magnesium precipitates
flame test
mg- no colour
ca- orange red flame
what happens if you add sodium hydroxide solution to a substance containing a) copper (ii) ions
b) iron (ii) ions
c) iron (iii) ions
a) blue precipitate appears
b) green precipitate
c) brown precipitate
what is the test for a carbonate
if you add dilute acid to a carbonate it will fizz and produce co2 gas
how can you differentiate group 1 carbonates from other carbonates
group 1 carbonates dissolve in water
what is the test for halides ( chlorides, bromides and iodides)
add dilute nitric acid and then silver nitrate solution and if a precipitate forms then it is a halide
