chemical analysis Flashcards
what is a pure substance
contains only one type of compound or element
physical properties of pure substances
- melt and boil at specific temperatures
- helps us identify what substance it is
impure substance properties
- melting point decreases
- boiling point increases
Formulation definition
mixtures that have been prepared using a specific formula
- precise amount of different
components
- have a particular function
chemical analysis
instruments and methods we use to identify, separate and quantify different substances
example of paint and why it has to be a formulation
- pigment
- solvent - to dissolve the other components
- binder - to stack onto the wall
test for chlorine
take a damp litmus paper into a test tube with the sample gas
- if chlorine is present the damp litmus
paper will turn blue to white
Why might the blue litmus paper turn red before turning white when testing for chlorine
The solution of chlorine is acidic
risk assessment of chlorine test
wear a mask as chlorine is poisonous
Test for oxygen
insert a glowing splint into a test tube with sample gas
- if oxygen is present the splint will
relight
Test for hydrogen
when a burning splint is placed near a test tube with hydrogen, there should be a squeaky pop
when testing for hydrogen, why is there a squeaky pop noise?
the heat energy from the flame causes the hydrogen to burn with the oxygen in the air to form water
When testing for oxygen, why does the splint relight
burning requires oxygen so providing a lot of O2 will spark up the reaction again
test for carbon dioxide
bubbling carbon dioxide through limewater causes the soultion to turn cloudy
When testing for carbon dioxide, why does calcium hydroxide turn cloudy?
calcium carbonate (product) is a solid and these solid particles makes it appear cloudy
what is a chromatogram
the pattern of spots on the filter paper after chromatography
mobile phase
where molecules can move
- liquid
- gas
stationary phase
where molecules cant move
- solid
- thick liquid
Rf value equation
distance travelled by solvent (H2o)
What is chromotography used for?
To separate a mixture of soluble substances in liquids
What are anions
negatively charged ions
carbonate reacting with acid word equation
carbonate + acid —->
salt + carbon dioxide + water
what do carbonate substances contain?
. -2
CO
3
test for carbonate ions
- use a pipette to add a few drops of
dilute HCL acid to a test tube
containing the sample - then bubble the test tube through lime
water - it will turn cloudy
sulfate ions
. -2
SO
4
test for sulfate
- using a pipette add few drops of dilute
HCL acid ( removes any other ions in
our sample ) - add few drops of barium chloride
solution - positive result = white precipitate
what are the halide ions
- chloride - ions
- iodide - ions
- bromide - ions
test for halides
- with pipette add few drops of dilute
nitric acid - add silver nitrate so the silver ions can
react with the halide to form a
precipitate - colour of precipitate depends on the
halide the silver ions react with
sulfate word equation
. +2 -2
Ba + SO —-> BaSO
4 4
chlorine colour precipitate
white
bromide colour precipitate
cream
iodide colour precipitate
yellow
what are cations?
positively charge ions
positive result for lithium flame test
crimson flame
positive result for sodium flame test
yellow flame
positive result for potassium flame test
lilac flames
positive result for calcium flame test
orange-red flame
positive result for copper flame test
green flame
what is a limitation of the flame test
if there are 2 or more different metals in the sample the colours of the flames will mix
calcium precipitate
white
copper precipitate
blue
iron II precipitate
green
iron III precipitate
brown
aluminium precipitate
colourless
magnesium precipitate
white
