chemical changes Flashcards
(24 cards)
what is a formulation
a formulation is a complex mixture that has beed designed as a useful product
what is chromatography
it is a technique to seperate substances based on their solubilities
what is the stationary phase in chromatography
the paper as it does not move
what is the mobile phase in paper chromatography
the solvent as it moves up the chromatogram
what is the formula for Rf value in paper chromatography
rf value (no units)= distance moved by substance/ distance moved by solvent
how can we ensure the accuracy of paper chromatography
use a capillary tube to ensure only allow a small spot of ink to be on the paper as this prevents the colours from spreading into eachother
put a lid on the beaker to reduce evaporation
what colour does lithium burn in a flame
crimson
what colour does sodium burn in a flame
yellow
what colour does pottasium burn in a flame
lilac
what colour does calcium burn in a flame
orange - red
what colour does copper burn in a flame
green
what is the limitations of flame tests
some colours are difficult to distinguish and some unknown compounds contain multiple metal ions
what is flame emmision spectroscopy
a metal ion in a solution is placed into a flame, the light then travells into a spectroscope which converts the light into a line spectrum (the positions of the lines in the specrtum are specific for a given metal ion). This can also tell us the concentration of that metal ion as the lines become thicker when more metal is present. This is an example of an insturmental method
what is an instrumental method and what are the advantages of instrumental methods
instrumental methods rely on machines and they are rapid, sensitive and accurate
how can we distinguish between aluminium sodium and potassium
we can add soidum hydroxide to form a white precipitate. If we add excess sodium hydroxide the alluminum precipitate will redissolve. We need to do flame tests to distunguish between the others
what colour precipitate is formed between the reaction of copper ions and sodium hydroxide
blue
what colour precipitate is formed between the reaction of iron (II) ions and sodium hydroxide
green
what colour precipitate is formed between the reaction of iron(II) ions and sodium hydroxide
brown
how do we test for carbonate ions
add dilute acid to the sample. This will cause fizzing, we can then bubble the gas into limewater to prove that carbon dioxide is being produced
how do we test for halide ions
add dilute nitric acid
add dilute silver nitrate
halide ions produce a precipitate of the silver halide. (each reaction produces a different coloured precipitate)
what colour precipitate do chloride ions make in the presence of silver nitrate and nitric acid
white
what colour precipitate do bromine ions make in the presence of silver nitrate and nitric acid
cream
what colour precipitate do iodine ions make in the presence of silver nitrate and nitric acid
yellow
how do we test for the presence of a sulfate ion
add dilute hydrochloric acid
add barium chloride solution
iff sulphapte ions are present, there will be a white precipitate
