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Identification of GASES
Gas Appearance Density Solubility Collection Test for Equation
Method Gas
Hydrogen Colourless Less dense Almost insoluble Over water OR A pop is heard 2H(g) + O(g)
than air in water upwards into when a lighted 2HO(l)
(H) test tube OR into splint is held
a gas syringe to the mouth
of the tube.
Oxygen Colourless Almost equal Only slightly Over water OR Will relight a _
density to air soluble in water into a gas syringe glowing splint
(O)
Carbon Colourless Denser than Only slightly Over water OR Limewater will Ca(OH)(aq)
air soluble in water into gas syringe go cloudy +CO(g)
Dioxide when CO is CaCO(s) +
(CO) bubbled HO(l)
through it:
Forms calcium carbonate
precipitate
Chlorine Green Denser than Quite soluble in Downwards into Will bleach _
air water test tube OR into damp litmus
(Cl) gas syringe paper
Ammonia Colourless Less dense Very soluble in Upwards into Alkaline so will _
than air water test tube OR into turn damp red
(NH) gas syringe litmus paper
blue.…read more

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Testing for Water
Anhydrous copper(II) sulfate Cobalt chloride paper
· White solid (powder like) · This is filter paper that has been dipped in
cobalt chloride solution and dried in a
· When water is added it goes blue dessicator.
· This is because dropping water onto it causes · A dessicator contains a substance that
it to form waters of crystallisation. absorbs water
· The equation for this is: · When dry, the paper is blue.
CuSO(s) + 5H0(l) CuSO·5H0(s)
· Adding water turns it pink
· The test works for anything that contains
water BUT it does not show whether the water · The test works for anything that contains
is pure. water BUT it does not show whether the water
is pure.
To check if a liquid is pure water, heat it until it boils which should be at 100 C at 1ATM…read more

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Testing for Cations (positive ions)
Add NaOH Warm until just boiling
solution. Does a NO and test with damp red
litmus paper. Does it go
precipitate form? blue?
YES
YES NO NH +
Flame test ­ Using a fresh sample. dip a
platinum or nichrome wire in HCl and hold in a
Bunsen until no colour is given to the flame. The
What colour is the wire is dipped back into the acid then into a
precipitate? small sample of the solid being tested and
returned to the flame. What colour is the
flame?
Brown/orange Lilac
Green Blue Orange/red
Red Orange (brick red)
Fe 2+ Fe 3+ Na +
Cu 2+ K+ Li + Ca 2+
The precipitates are the ion hydroxide e.g.
Iron (II) hydroxide, Fe(OH)2…read more

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Testing for Anions (negative ions)
Dissolve the solid. Add a few
drops of dilute nitric acid and NO
a few drops silver chloride
solution and gently shake.
Does a precipitate form?
Dissolve a fresh sample of
YES solid. Add a few drops of NO
barium chloride solution and a
few drops dilute HCl and shake.
White Yellow Does a white precipitate form?
Cream
Dissolve a fresh sample of solid
YES in HCl. Look for bubbles of gas
Cl - being produced. Collect gas
Br - I- and bubble through limewater.
SO 2- Does it go cloudy?
The precipitates are the Silver ion
e.g. Silver Chloride, AgCl Barium Sulfate forms.
YES
NO
CO 2- Unknown
First carbon dioxide and water form, then the
carbon dioxide reacts with the limewater to form
a precipitate of calcium carbonate.…read more

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