(a) describe the use of aqueous sodium hydroxide and aqueous ammonia to identify the following aqueous cations: aluminium, ammonium, calcium, copper(II), iron(II), iron(III), lead(II) and zinc (formulae of complex ions are not required)
(b) describe tests to identify the following anions: carbonate (by the addition of dilute acid and subsequent use of limewater); chloride (by reaction of an aqueous solution with nitric acid and aqueous silver nitrate); iodide (by reaction of an aqueous solution with nitric acid and aqueous lead(II) nitrate); nitrate (by reduction with aluminium and aqueous sodium hydroxide to ammonia and subsequent use of litmus paper) and sulfate (by reaction of an aqueous solution with nitric acid and aqueous barium nitrate)
(c) describe tests to identify the following gases: ammonia (using damp red litmus paper); carbon dioxide (using limewater); chlorine (using damp litmus paper); hydrogen (using a burning splint); oxygen (using a glowing splint) and sulfur dioxide (using acidified potassium dichromate(VI))
O Level - Combined Chemistry
(a) describe the use of aqueous sodium hydroxide and aqueous ammonia to identify the following aqueous cations: ammonium, calcium, copper(II), iron(II), iron(III), lead(II) and zinc (formulae of complex ions are not required)
(b) describe tests to identify the following anions: carbonate (by the addition of dilute acid and subsequent use of limewater), chloride (by reaction of an aqueous solution with nitric acid and aqueous silver nitrate), nitrate (by reduction with aluminium and aqueous sodium hydroxide to ammonia and subsequent use of litmus paper) and sulfate (by reaction of an aqueous solution with nitric acid and aqueous barium nitrate)
(c) describe tests to identify the following gases: ammonia (using damp red litmus paper), carbon dioxide (using limewater), chlorine (using damp litmus paper), hydrogen (using a burning splint), oxygen (using a glowing splint) and sulfur dioxide (using acidified potassium dichromate(VI))
N(A) Level - Combined Chemistry
(a) describe tests to identify the following gases: carbon dioxide (using limewater), hydrogen (using a burning splint), oxygen (using a glowing splint)
-Syllabuses from SEAB
Why is iodide sometimes brown and sometimes yellow and sometimes blue?
ReplyDeleteHi, you need to draw a distinction between iodide and iodine.
DeleteIodide, I-, is an anion. Silver iodide and Lead (II) iodide are yellow solids.
Iodine, I2, is a diatomic molecule. It is a Group 7 halogen. In the solid state, iodine is blue-black. In gasesous state, iodine is purple. When dissolved in some organic solvents, iodine is brown.
To assign the colour carefully, you have to
1) identify whether you're talking about Iodide or Iodine
2) assign the colours carefully.