Method Positive result Hydrogen Squeaky pop lit splint High pitched pop Oxygen Glowing splint Splint relights Carbon dioxide Bubble gas through lime water Dilute calcium hydroxide Ca OH ID: 930093
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Slide1
Testing for Gases
Gas
test
Method
Positive result
Hydrogen
Squeaky pop, lit splint
High pitched pop
Oxygen
Glowing splint
Splint relights
Carbon dioxide
Bubble gas through lime water ( Dilute calcium hydroxide Ca (OH)
2
)
Lime water turns cloudy
Chlorine
Using damp litmus paper hold into gas
It turns it white
Slide2Gas tests link
https://www.youtube.com/watch?v=jVkGKurtaiE
https://www.youtube.com/watch?v=fCZztwJmAl0
Slide3Safety precautions:
Use small quantities
How flammable the gas
Do you need to use a fume cupboard
Is it an irritant
Wear googles
tongs
Slide4Identifying ions
Type of Halide ion (anions -negative ions)
Positive result
Chloride
White precipitate
Bromide
Cream precipitate
iodideYellow precipitate
Nitric acid is added to the test as it is a catalyst
Each sodium salt was added to distilled water ( No other ions to interfere with the test)
The test solution
Silver Nitrate
The precipitates are silver chloride, silver bromide or silver iodide –THESE ARE ALL INSOLUBLE
Slide5Starter- books on the floor under desks (even you Marcus)
On scrap paper complete the following table:
Type of Halide ion (anions -negative ions)
Positive result
Chloride
Bromide
iodide
Type of Halide ion (anions -negative ions)
Positive result
Chloride
Bromide
iodide
What two solutions do you need for the anion tests?
Slide6Outcomes
All
to
recall that
flame
tests can be used to identify some metal ions (cations). Lithium, sodium, potassium, calcium and copper compounds
to explain that if a sample containing a mixture of ions is used some flame colours can be maskedMost to be able to interpret an instrumental result given appropriate data in chart or tabular form, when accompanied by a reference set in the same form, limited to flame emission spectroscopySomeTo explain how flame spectroscopy actually works
Slide7Flame test for metals
Metal
Colour of flame
Lithium
Crimson flame (red)
Sodium
Yellow
FlamePotassiumLilac FlameCalcium
Orange
red flame
Copper
Green flame
Which splint is which type of metal?
Slide8So what would you see if you had more than one metal present in solution?
Slide9Colour masking
If there is a combination of metals present in a solution the colours may mask each others.
Eg
the most vibrant colour will over shadow others so flame test by itself are not the most effective analytical tool
Slide10Flame Emission spectroscopy
All ions have a different electron configuration on their shells
When you heat ions up the electrons get excited and swap shells or
energy level
When the electron drop back into place the energy is transferred into light
Different electrons combinations will therefore emit different patterns of light a bit like a fingerprint
Slide11Slide12EmissionSpectroscopy
Slide13How to read an spectroscopy graph
Slide14Now have a go at the exam questions!
Slide15Cation – metal precipitate tests
Metal Ion
Colour of the Precipitate
Ionic precipitation formula
Calcium Ca2+
White
Ca(OH)
2(s)Copper Cu 2+BlueCu(OH)2(s)
Iron Fe2+
Green
Fe(OH)
2(s)
Iron Fe3+BrownFe(OH)3(s)Aluminium Al 3+White and then clearAl(OH)3(s)Magnesium Mg 2+White
Mg(OH)
2(s)
This is a displacement reaction with sodium hydroxide
Metal hydroxides are insoluble so they form solid precipitate
Slide16Indicators
Type of indicator
Colour change
Universal
Acids are red 1-6
Neutral green 7
Alkali are blue purple 8-14
Red litmusAcids redNeutral RedAlkali BlueBlue Litmus
Acid red
Neutral
blue
Alkali blue