C9 Seperate chemistry 2 Flashcards
How small are nanoparticles?
1-100 nanometres
Nanoparticles have a very _____ SA:VOL
large
How do you figure out SA:VOL of cubic nanoparticle?
e.g. sidelength 20nm
- area of cube face
- area if 6 cube faces
- volume if cube
- SA:VOL ratio
- Divide by bolume so we can compare
e. g.
1. A=20x20 = 400nm^2
2. A=6x400 = 2400nm^2
3. V= 20x20x20 = 8000nm^3
4. 2400 : 8000
5. 0.3 : 1
What happens to SA:VOL ratio if we half the size if our nanoparticle?
SA:VOL ratio increases by factor of 2
Why do we add nanoparticles to sunscreen?
- absorb/block UV light from the skin which prevents sunburn
- very small so cannot be seen on skin
Why do nanoparticles make good catalysts?
- reactions occur on the surface if catalysts
- nanoparticles have a large SA:VOL ratio
- Larger SA means more successful collisions will occur
- Which increases RoR
- Large SA:VOL means only small quantity needed
What are the disadvantages of nanoparticles? (3 points)
- new technology
- thus we dont know the long term risks
- nanoparticles are so small they could pass into our cells/bloodstream
- so they could change the nature of chemical reactions in our body
- nanoparticles can be washed into the environment
- so they can end up in other organisms
- and build up in food chains causing problems
What are polymers?
- long chain carbon molecules
- made up of monomers
- held together by strong covalent bonds
What are examples of polymers?
- polyester
- LDPE
- HDPE
- polystyrene
- polypropene
- polytetrafluroethene(PTFR/Teflon)
- polychloroethene(polyvinyl chloride/PVC)
What are ceramics?
- non-metallic
- inorganic (non-carbon)
- solids
- made from metal/non-metal compunds that have been shaped and then hardened by heating to high tmeperatures
What are some examples of ceramics?
-clay ceramics
a mineral made from weathered and decomposed rock – soft and mouldable until heated
-glass
made from limestone, sand and sodium carbonate which is heated until it melts
What are composites?
- made from fibres of fragments of one material (the reinforcement)
- embedded into another material (matrix/binder)
What are examples of composites?
-fibreglass
glass embedded in polymer
-carbon fibres
long chains of carbon embedded in polymer
-concrete
sand and gravel embedded in cement
What are metals?
naturally occuring elements extracted from ores
What is tensile strength?
how easily something can break/shatter
low = easy to break/stretch/shatter high = hard to break/stretch/shatter
What ions does the flame test test for?
- lithium
- calcium
- sodium
- copper
- potassium
Why must the test for ions be unique?
- when electrons lose energy it will drop down to a lower energy level
- it will lose energy equal to the difference between two energy levels
- energy emitted in form of visible light unique to each element
therefore
the test must be an easy-to-observe result that is specific to the ion present
What ion is present if a red flame is produced?
Lithium
What ion is present if a red-orange flame is produced?
Calcium
What ion is present if a yellow flame is produced?
Sodium
What ion is present if a green-blue flame is produced?
Copper
What ion is present if a lilac flame is produced?
potassium
What colour will Lithium produce in a flame test?
red
What colour will Calcium produce in a flame test?
red-orange
What colour will Sodium produce in a flame test?
yellow
What colour will Copper produce in a flame test?
green-blue
What colour will Potassium produce in a flame test?
lilac
What is the test used to identify the pressence of Lithium ions?
flame test
What is the test used to identify the pressence of Calcium ions?
flame test
What is the test used to identify the pressence of sodium ions?
flame test
What is the test used to identify the pressence of Copper ions?
flame test
What is the test used to identify the pressence of Potassium ions?
flame test
What does a metal and hydroxide form?
metal + hydroxide -> metal hydroxide
How do you test for Aluminium ions and what colour will the precipitate be?
- add hydroxide
- white
- add NaOH
- colourless solution
How do you test for Calcium ions and what colour will the precipitate be?
- add hydroxide/ NaOh
- white
How do you test for Copper ions and what colour will the precipitate be?
- add hydroxide/ NaOH
- blue
How do you test for Iron(II) ions and what colour will the precipitate be?
- add hydroxide/ NaOH
- green
How do you test for Iron(III) ions and what colour will the precipitate be?
- add hydroxide/NaOH
- brown
How do you test for NH4 ions and what colour change occurs?
- Add hydroxide to the solution in a test tube
- Gently heat -> produce ammonia gas
- Damp piece of red litmus paper over end of the test tube
- Litmus paper turns blue if ammonia gas is present
- Ammonium ions are present if colour change occurs
- litmus paper
- red -> blue
How do you test for carbonate ions?
-add acid
metal carbonate + acid –> metal salt + carbon dioxide + water
–CO2 will form bubbles in solution
test for CO2
- bubble gas through limewater
- turns cloudy
therefore
- react unknown solid/solution with hydrochloric acid
- see bubbles indicating gas
- if gas turns limewater cloudy C02 present
- unknown sample contains CO3 ions
How do you test for sulfate ions?
-barium sulphate is insolube
- add HCl beforehands
- react with and remove carbonate ions present which would also produce white precipitate
- add barium ions
- to an unknown solution
- white perticipate forms
How do you test for halide (chloride, bromide, iodide) ions and what colour change occurs?
- add HNO3/ dilute nitric acid
- add AgNO3/ silver nitrate
- colour change
chloride - white
bromide - cream
iodide - yellow
exam style question:
identify the salts
salt A
flame test - red flame
dilute nitric acid + silver nitrate solution added - cream percipitate
salt B
flame test - no change to colour
NaOH added - green precipitate formed
dilute nitric acid + silver nitrate solution added - no reaction
acidified with dilute hydrochloric acid and aqueous barium chloride added - white precipitate formed
salt A
1st test - lithium ions
2nd test - bromide ions
salt A - lithium bromide
salt B 1st test - no Li, Ca, Na, Cu, K ions 2nd test - Fe(II) ions 3rd test - no halide (Cl, Br, I) ions 4th test - sulfate ions
salt B - iron sulfate
What does the intensity of spectra line tell us? (flame photometry)
- indicates the concentration
- concentration can be found using a calibration curve
What are 3 advantages of using instrumental analysis?
-very fast
automated –improves the speed
-very accurate
removes chance of human error
-very sensitive
instrumental tests like flame photometry can detect the tiniest amount if a substance
How big are nanoparticles in comparison to atoms?
10-100 times bigger
