Tests for ions Flashcards
Give the test for halide ions and the results
Add acidified silver nitrate solution
Cl⁻ → white ppt
Br⁻→ off white / cream ppt
I⁻→ yellow ppt
Give the simplest ionic equation for the test of a halide ion: X⁻
(X⁻ is not fluoride)
Ag⁺(aq) + X⁻(aq) → AgX(S)
(AgF would be (aq))
Which halide ion produces a white ppt in acidified silver nitrate solution?
Cl⁻
Which halide ion produces a cream ppt in acidified silver nitrate solution?
Br⁻
Which halide ion produces a yellow ppt in acidified silver nitrate solution?
I⁻
Why do fluoride ions not produce a ppt in acidified silver nitrate solution
AgF is soluble
Give 2 observations when acidified silver nitrate is added to a solution containing halide ions and carbonate ions
Effervescence / bubbling
(Carbonate ions react with acid to produce CO₂)
Coloured ppt
(Ag⁺ reacts with halide ion)
How can ammonia distinguish silver halide precipitates?
AgCl dissolves in some NH₃
AgBr dissolves in excess NH₃
AgI is insoluble in NH₃
Why does silver nitrate need to be acidified to test for halide ions?
To prevent the formation of AgCO₃ which is a white solid. (would confuse the results)
What is the test for ammonium (NH₄⁺) ions?
Add NaOH solution and warm the mixture. A gas is produced (NH₃) that turns red litmus paper blue (it is basic)
Give the simplest ionic equation for the test for ammonium ions
NH₄⁺(aq) + OH⁻(aq) → NH₃(g) + H₂O(l)
Give the test for carbonate ions (CO₃²⁻)
Add an acid - bubbles formed.
Bubbling gas through limewater will turn it cloudy, proving the gas produced is CO₂
Give the simplest ionic equation for the test for carbonate ions
2H⁺(aq) + CO₃²⁻(aq) → H₂O(l) + CO₂(g)
Give the test for hydroxide ions
Add a solution of Mg²⁺ ions. Forms a white ppt of Mg(OH)₂
Give the simplest ionic equation for the test for hydroxide ions
Mg²⁺(aq) + 2OH⁻(aq) → Mg(OH)₂(s)