Chapter 2.18 Chemical tests - Summary Pearson Edexcel International GCSE (9-1) Chemistry Student Book - Chemistry

2 - 18 Chemical tests


Tests for gases

● Hydrogen (H2)
○ Properties:
■ Colourless
■ Odourless
■ Very light
■ Very flammable
○ Lighted splint, ignites with squeaky pop
○ 2HCl (aq) + Mg (s) → MgCl2 (aq) + H2 (g)
○ 2H2 (g) + O2 (g) → 2H2O (l)


● Oxygen (O2)
○ Properties:
■ Colourless
○ Relights glowing splint
○ 2H2O2 → 2H2O (l) + O2 (g)


● Carbon dioxide (CO2)
○ Properties:
■ Colourless
○ Bubble gas through limewater, turns limewater cloudy/milky
■ CaCO3 + 2HCl → CaCl2 + H2O + CO2
○ Ca(OH)2 (aq) + CO2 (g) → CaCO3 (s) + H2O (l)


● Chlorine (Cl2)
○ Properties:
■ Pale green gas
■ Pungent (choking smell)
○ Bleaches damp litmus paper/universal indicator paper
■ E.g.: blue litmus paper → red → white




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, ○ 2KMnO4 + 16HCl → 2MnCl2 + 2KCl + 8H2O + 5Cl2


● Ammonia (NH3)
○ Properties:
■ Colourless
■ Pungent
○ Turns damp red litmus blue (alkaline gas)


● Nitrogen dioxide (NO2)
○ Cu + 4HNO3 → Cu(NO3)2 + 2H2O + 2NO2



Test for water
● Turns white anhydrous copper (II) sulphate blue
● (TB) CuSO4 (s) + 5H2O (l) → CuSO4•5H2O (s)
(SBA) CoCl2•2H2O (blue/white) → CoCl2•6H2O (red)


● Test for water purity
○ Pure water freezes/melts (for ice) at exactly 0˚C, boils exactly 100˚C (at 1
atm)
○ If water impure, freeze at lower temperature, boil at higher temperature
○ Test: measure boiling point (as when reached boiling point, temperature will
be same for a period of time)



Tests for ions
● .




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