Tests for ions Flashcards

1
Q

Give the test for halide ions and the results

A

Add acidified silver nitrate solution

Cl⁻ → white ppt
Br⁻→ off white / cream ppt
I⁻→ yellow ppt

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2
Q

Give the simplest ionic equation for the test of a halide ion: X⁻

(X⁻ is not fluoride)

A

Ag⁺(aq) + X⁻(aq) → AgX(S)

(AgF would be (aq))

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3
Q

Which halide ion produces a white ppt in acidified silver nitrate solution?

A

Cl⁻

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4
Q

Which halide ion produces a cream ppt in acidified silver nitrate solution?

A

Br⁻

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5
Q

Which halide ion produces a yellow ppt in acidified silver nitrate solution?

A

I⁻

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6
Q

Why do fluoride ions not produce a ppt in acidified silver nitrate solution

A

AgF is soluble

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7
Q

Give 2 observations when acidified silver nitrate is added to a solution containing halide ions and carbonate ions

A

Effervescence / bubbling
(Carbonate ions react with acid to produce CO₂)
Coloured ppt
(Ag⁺ reacts with halide ion)

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8
Q

How can ammonia distinguish silver halide precipitates?

A

AgCl dissolves in some NH₃
AgBr dissolves in excess NH₃
AgI is insoluble in NH₃

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9
Q

Why does silver nitrate need to be acidified to test for halide ions?

A

To prevent the formation of AgCO₃ which is a white solid. (would confuse the results)

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10
Q

What is the test for ammonium (NH₄⁺) ions?

A

Add NaOH solution and warm the mixture. A gas is produced (NH₃) that turns red litmus paper blue (it is basic)

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11
Q

Give the simplest ionic equation for the test for ammonium ions

A

NH₄⁺(aq) + OH⁻(aq) → NH₃(g) + H₂O(l)

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12
Q

Give the test for carbonate ions (CO₃²⁻)

A

Add an acid - bubbles formed.
Bubbling gas through limewater will turn it cloudy, proving the gas produced is CO₂

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13
Q

Give the simplest ionic equation for the test for carbonate ions

A

2H⁺(aq) + CO₃²⁻(aq) → H₂O(l) + CO₂(g)

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14
Q

Give the test for hydroxide ions

A

Add a solution of Mg²⁺ ions. Forms a white ppt of Mg(OH)₂

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15
Q

Give the simplest ionic equation for the test for hydroxide ions

A

Mg²⁺(aq) + 2OH⁻(aq) → Mg(OH)₂(s)

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16
Q

Give the test for sulfate ions

A

Add acidified barium chloride solution. White ppt of BaSO₄ formed

17
Q

Give the simplest ionic equation for the test for sulfate ions

A

Ba²⁺(aq) + SO₄²⁻(aq) → BaSO₄(s)

18
Q

Why does barium chloride need to be acidified in the test for sulfate ions?

A

To prevent the formation of Ba(CO₃)₂ which is a white solid and could give a false positive

19
Q

Give two sources of aqueous sulfate ions

A

Solutions of group 1 sulfate salts (eg NaSO₄)
Sulfuric acid

20
Q

How would you prepare an inorganic solid for testing

A

Dissolve in water (Grind in pestle and mortar first if necessary)