Chemical Analysis (Paper 2) Flashcards
In paper chromatography, the solvent used is known as the what phase
Mobile
Substance that limewater tests for
Carbon dioxide
Which gas would you test for with a glowing splint
Oxygen
Formulation meaning
A mixture that has been designed as a useful product
Name for mixture that has been designed as a useful product
Formulation
What is a pure substance
A substance that is made up of only one type of element or compound
Name for type of substance that is made up of only one type of element or compound
Pure substance
How to test for carbon dioxide
Bubble through limewater
How to test for oxygen
Put a glowing splint inside the tube
How to test for hydrogen
Put a lighted splint inside the tube
Glowing splint meaning
A splint that has been lit and burnt for a few seconds then blown out (can be used to test for oxygen when put inside the tube)
Result for carbon dioxide test
Turns limewater cloudy
What happens to the limewater when carbon dioxide is present
Turns cloudy
Result for when oxygen is present
Relights a glowing splint
Result for when hydrogen gas is present
Makes a squeaky pop noise
Carbon dioxide test and result
Bubble through limewater
Limewater turns cloudy
Oxygen test and result
Put a glowing splint (one that has been burnt then blown out) inside the tube
Re- lights the glowing splint
Hydrogen test and result
Put a lighted splint inside the tube
Makes a squeaky pop noise
Only what type of substances melt and boil at specific temperatures
Pure substances
What temperature does water boil at
100 degrees Celsius
True or false, impure substances (e.g sodium chloride mixed with water) have fixed melting and boiling points
False,
Only pure substances like the pure water on its own or pure sodium chloride on its own have fixed melting and boiling points
True or false, formulations have been designed to have precise amounts of differnt components and therefore have a specific function
True
(Hence the name- they have a specific formula)
True or false, in formulations each different component is always included in the same proportion
True
(Each component may contribute to a different property to help with the overall function e.g paint/ medicine)
Chemical analysis (also called analytical chemistry) is about what
The instruments and methods we use to separate, identify and quantify different substances
True or false, a pure substance can be both an element or a compound
True
As long as it doesn’t have anything mixed into it but is made of just that single thing
If a substance melts over a range of temperatures is it a pure substance
No, it’s impure
Pure substances always melt at the same specific melting point
Is measuring a substance’s boiling point a chemical or physical test
Physical
True or false, there are lots of different types of chromatography, not just paper
True
E.g gas chromatography, but the only one we need to know about is paper chromatography
(Chromatography is a way of separating different components of a mixture)
Name for line that you draw at base of sheet with pencil in paper chromatography
Baseline
First step in paper chromatography
Take filter paper and draw horizontal line (baseline) with pencil near the bottom
How much solvent (e.g water/ ethanol) should you add to the beaker for paper chromatography
Shallow amount
Examples of 2 solvents to use in beaker for paper chromatography
Water/ ethanol
Stages for paper chromatography
1) take filter paper and draw horizontal line in pencil near the bottom (baseline)
2) add a dot of your sample e.g ink to the middle of the pencil line
3) place paper in beaker with shallow amount of solvent (e.g water) ensuring that the pencil line and ink aren’t submerged
4) place lid on top of beaker to stop solvent from evaporating
5) wait for solvent to seep up paper- the different dyes in the ink will dissolve in the solvent and move up the paper with it
6) different dyes move up paper at different rates (are separated)
7) once solvent has neatly reached top of paper, take paper out of beaker and leave to dry
Why should a lid be placed on the beaker in paper chromatography
Stop the solvent from evaporating
True or false, the baseline containing the ink sample in paper chromatography should be submerged in the solvent
False
It needs to be above the solvent which is why you only add a shallow amount to the beaker
2 types of phases in paper chromatography
Mobile phase
Stationary phase
Mobile phase meaning in paper chromatography
The solvent
(When the molecules in the sample e.g ink can move)
Stationery phase meaning in paper chromatography
The paper
Substance/ material that the molecules from the sample (e.g ink) can’t move in
What phase is the paper in paper chromatography
Stationery phase
As the molecules can’t move
In paper chromatography what stage is the paper and what stage is the solvent
Paper= stationery phase (molecules can’t move)
Solvent= mobile phase (molecules can move)
In paper chromatography do the more soluble components move further up the paper or not
Yes, further as they spend more time in the mobile phase (solvent) so moving up the paper
In paper chromatography do less soluble components move further up the paper or not
No, they spend more time in the stationery phase so staying still on the paper instead of moving up the paper in the solvent
How to calculate Rf value (ratio of how far component moves compared to solvent)
Distance travelled by substance/ distance travelled by solvent
2 things that must be taken into account when looking at Rf value
Solvent used
Type of paper used
(As these may alter the mobile and stationery phase and therefore Rf value, even if you’re using the same pure substance e.g pure water both times)
Why should we use pencil for the baseline not pen
Pen would dissolve in the solvent so move up the paper
How to test for chlorine
Take damp blue litmus paper and place in test tube that’s suspected to have chlorine gas in
Result for chlorine test
Damp blue litmus paper turn white
Chlorine test and result
Take damp blue pice of litmus paper and place in test tube
If chlorine is present litmus paper will turn white (is bleached)
(It may temporarily turn red before turning white due to hydrochloric acid being formed)
(Wear mask as chlorine gas is poisonous)
Another name for limewater
Calcium hydroxide
Another name for calcium hydroxide
Limewater
2 safety precautions for when testing for chlorine gas
Wear gas mask
Do experiment in a fume cupboard
What is the first way we test for positive ions
Flame test
Are anions positive or negative ions
Negative
Are cations positive or negative ions
Positive
Which out of anions and cations are positive or negative ions
Anions= negative ions
Cations= positive ions
3 types of negative ions we test for
Halide
Sulfate
Carbonate
How to test for carbonate and why
Hydrochloric acid (add to sample with suspected carbonate in)
When a carbonate + acid react together it produces carbon dioxide, a salt and water
Bubble gas through limewater
If limewater turns cloudy then carbon dioxide is present meaning that it must have been carbonate as carbonate produces the carbon dioxide
2 steps for testing for carbonates
1) add hydrochloric acid to test tube
2) bubble gas that’s produced through limewater
Positive result= limewater goes cloudy due to gas being CO2 which is released from the carbonate reacting with the acid
2 steps for testing for sulphates
1) Add hydrochloric acid to test tube
2) Add barium chloride solution to same test tube
Positive result= white precipitate formed
3 halide ions we test for
Iodide
Chloride
Bromide
How to test for halide ions (bromide, iodide and chloride)
Add dilute nitric acid to remove any impurities (carbonate and sulphite ions) that could form a precipitate and give a false positive result
Add silver nitrate- halide ions react with silver to form different colour precipitates
Iodide= yellow
Chloride= white
Bromide= cream
What colour precipitate does (silver) iodide form
Yellow
What colour precipitate does (silver) bromide form
Cream
What colour precipitate does (silver) chloride form
White
What colour precipitates do chloride, bromide and iodide ions form
Chloride= white
Bromide= cream
Iodide= yellow
When testing for halide ions what do the halide ions react with to form the differnt coloured precipitates
Silver in the silver nitrate
(Forms silver iodide/ silver bromide/ silver chloride)
When testing for sulphate ions what do the sulphate ions react with to form the white precipitate
Barium ions in the barium chloride
Along with silver nitrate (for halide ions) and barium chloride (for sulphate ions) why is a dilute acid also needed
Remove any impurities like carbonate ions an sulfate ions which could also react with the barium/ silver to form a precipitate and give off a false positive result
2 ways to collect gas when testing for carbonate
Attach top of test tube to gas syringe
Place upside down measuring cylinder over test tube to trap the gas
2 ways to test for positive ions
Flame test
Sodium hydroxide
What colour flame does lithium go
Crimson
(Chile- Li at end for lithium and Chile is crimson coloured)
What colour flame does Sodium go
Yellow
(Banana- has Na in it for sodium and banana is yellow)
What colour flame does potassium go
Lilac- plum has p in it for potassium and plum is lilac coloured
What colour flame does calcium go
Orange/ red
Carrot- has Ca in it for calcium and carrot is orange
What colour flame does copper go
Green
Cucumber- has Cu in it for copper and is green
What do we do to test for positive metal ions if there was no positive result from the flame test (or if the flame was red which means it could be either lithium or calcium)
Add a few drops of sodium hydroxide
What colour precipitate does magnesium form
White
What colour precipitate does calcium form
White
What colour precipitate does copper form
Blue
What colour precipitate does iron 2 form
Green
What colour precipitate does iron 3 form
Brown
What colour precipitate does aluminium form
White (dissolves in excess)
Which 3 metals form white precipitates
Magnesium
Calcium
Aluminium (dissolves in excess)
Which metal forms a white precipitate that dissolves in excess
Aluminium
2 metals that form white precipitates and don’t dissolve in excess
Calcium
Magnesium
Metal that forms blue precipitate
Copper
Metal that forms green precipitate
Iron 2
Metal that forms brown precipitate
Iron 3
Metal that gives crimson flame
Lithium
Metal that gives yellow flame
Sodium
Metal that gives lilac flame
Potassium
Metal that gives orange/ red flame
Calcium
Metal that gives green flame
Copper
Negative ion used to test for with barium chloride and hydrochloric acid
Sulphate ions
Negative ion used to test for with hydrochloric acid (and then limewater)
Carbonate
Negative ion used to test for with nitric acid and silver nitrate
Halide ions (bromide, chloride and iodide)
Chemical analysis is about the instruments and methods used to…..
Separate, identify and quantify different chemicals
A pure substance is a substance made up of only one type of element or…
Compound
