.
To
test for acid you use blue litmus paper which turns red with the presence of
acid.
To
test for alkali you use red litmus paper which turns blue with the presence of
alkali.
If
you test an acid or alkali with universal indictor you will be able to see what
its pH is.
These
are tests for metals and their compounds :
-
Amphoteric compounds (Al and Zn compounds). To test for Al and Zn compounds you
add NaOH to the substance and a white precipitate should form . If you then add
excess NaOH the white precipitate will dissolve if the substance is an
amphoteric compound.
Flame
test for metals:
-Lithium
goes crimson in a flame.
-Sodium
goes yellow in a flame.
-Potassium
goes lilac in a flame.
-Rubidium
goes red in a flame.
-Caesium
goes blue in a flame.
-Copper
goes green/blue in a flame.
-Calcium
goes brick red in a flame.
-Barium
goes apple green in a flame.
-Strontium
goes crimson in a flame.
-Iron
compounds can be easily detected in a test as the solution is neither green or
brown . Green occurs if iron (II) ions are present and brown occurs if iron
(III) ions are present.
-To
test for halide ions in solutions you add silver nitrate solution to your test
solution . Examples of this test is bromine ,chlorine and iodine. If you add
silver nitrate to a solution containing chloride ions you get a white
precipitate. For the bromide ions you will get a cream precipitate and for the
iodide ions you get a yellow precipitate .
A
easy way to remember this is "why can't You" . The w of the why means
white ,the c of can't means cream and the y of you means yellow.
-To
test for lead in a solution we add the solution to Sodium hydroxide and if lead
is present then a white precipitate should be formed.
The
tests for non metals and different compounds:
-To
test for sulphuric acid you add a barium salt to the solution of suspected
sulphuric acid and if sulphuric acid is present then a white precipitate called
Barium sulphate is form.
BaClı
+ HıSO = BaSO
+ 2HCl
-To
test for Hydrogen sulphide you add aqueous lead nitrate to the suspected
Hydrogen sulphide and if Hydrogen Sulphide is present then
a black precipitate of Lead sulphide is formed.
-To
test to see if a solution is an alkene you would add it to brown bromine and if the bromine turn colourless then
the solution is an alkene.
-To
test to see if a solution is a reducing agent you would add it to purple
potassium permanganate and if the potassium permanganate turns colourless then
the solution is a reducing agent.
-To
test to see if a solution is a oxidising agent
you would add it to green iron (II) oxide and if the green iron (II)
oxide turns into brown iron (III) oxide then the solution is a oxidising agent.
-To
test to see if oxygen is present you put a glowing splint into the test tube of
oxygen and if the splint relights then oxygen is present.
-To
test for hydrogen you put a lighted splint into a test tube and if the a pop
occurs inside the test tube then hydrogen is present.
-To
test to see if a gas is carbon dioxide you bubble the gas through clear lime
water (Calcium hydroxide) and if
the lime water goes cloudy then carbon dioxide is present.
-To
test to see if a solution is hydrochloric acid you put blue litmus into it and
if it turns red then Hydrochloric acid is the solution.
-To
test to see if a solution is ammonia then you put hydrogen chloride beside it
and if a white smoke is formed then the solution is ammonia.
-To
test to see if a solution is sulphur dioxide you put the solution on to purple
potassium permanganate on filter paper and if the solution id sulphur dioxide
then the potassium permanganate on the filter paper should be colourless.
-To
test for Chlorine you put a suspected solution
on to potassium iodide on filter paper which turn brown to indicate the
present of Chlorine.
-To
test for nitrogen dioxide you add it to copper and if the copper goes green then
nitrogen dioxide is present.
-To
test for water you add the solution to anhydrous copper sulphate (white) and if
water is present the white copper sulphate will turn blue.
You
can test a chemical by looking at its physical features e.g. colour, smells and
if gases can be see evolving for it.
Loreto College, Coleraine.