C8 Chemical analysis Flashcards
What is a pure substance?
a substance with only 1 element/compound throughout
How can we test how pure a substance is?
we can compare MP/BP and the closer to the actual value, the purer it it.
What is the effect of impurities on the melting point?
impurities lower the melting point
What is the effect of impurities on the boiling point?
impurities increase the boiling point of a sample
what are formulations?
useful mixtures made of exact amounts of components
What is in the formulation of paint?
pigment
solvent
binder
additives
Why are formulations useful in the pharmacutical industry?
so chemists can ensure drugs are delivered to the correct part of the body, at the right concentration and has a long shelf life
What is chromatography?
a method to seperate the substances of a mixture
what are the 2 phases in chromatography?
a mobile phase
a stationary phase
how do you calculate the Rf value from chromatography?
distance travelled by solvent
What has to be done to make chromatography useful?
test a pure substance next to it so you can compare
What is the test for chlorine?
bleeches damp litmus paper white
What is the test for oxygen?
ignites a glowing splint
What is the test for carbon dioxide?
turns lime water (calcium hydroxide) cloudy
What si the test for hydrogen?
makes a squeaky pop when ignited with a lit splint
What are the 3 test for anions?
dilute acid-to test for carbonates
barium chloride and HCL- can test for sulphates
nitric acid and silver nitrate can test for halides
How can you test for carbonates?
add dilute acid and see if it turns limewater cloudy as co2 is released
How can you test for sulfates?
add a few drops on HCL and a few drops of barium chloride. a white precipitate will form if sulfate ions are present
How can you test for halides
add a few drops of nitric acid and silver nitrate.
the colour of precipitate determines the halide ion
In a halide ion test, what precipitates do chloride ions form?
white
In a halide ion test, what precipitates do bromide ions form?
cream
In a halide ion test, what precipitates do iodide ions form?
yellow
What colour flame to lithium ions burn with?
crimson
What colour flame to sodium ions burn with?
yellow
What colour flame to potassium ions burn with?
lilac
What colour flame to calcium ions burn with?
orange-red
What colour flame to copper ions burn with?
green
Why do you clean the loop in HCL in flame tests?
to ensure the loop isnt contaminated
What is a disadvantage of flame tests?
you can only detect samples that contain a single metal ion and not a mixture
what 2 ways can you test for cations?
flame tests
adding NaOH
What colour precipitate does calcium form when NaOH is added?
white
What colour precipitate does copper form when NaOH is added?
blue
What colour precipitate does iron(II) form when NaOH is added?
green
What colour precipitate does iron (III) form when NaOH is added?
brown
What colour precipitate does magnesium form when NaOH is added?
white
What colour precipitate does aluminium form when NaOH is added?
White at first but then redissolves in excess NaOH to form a colourless soloution
What is flame emission spectroscopy?
when a sample is placed in a flame. as the ions heat up, their electrons become excited. when they then drop down to their original energy level, they transfer energy as light which can pass through a stechoscope ad detect different wavelengths of light
What does the combination of a wavelength emitted by an ion?
is charge and electron arrangement.
What can flame emission spectroscopy be used for?
identifying ions in solutions and calculating concentrations
Why are machines used for analysing unknown substances (instrumental analysis)?
very sensitive
very fast
very accurate
Does flame emission spectroscopy work for mixtures?
yes- this is why its more useful than flame tests
