Test for ions Flashcards

1
Q

Test for halide ions

A

React with acidified silver nitrate solution. Forms coloured precipitate

Ag+(aq) + X-(aq) —> AgX(s)

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2
Q

Precipitate colours for halide test

A

AgCl - white
AgBr - Cream
AgI - yellow
AgF - soluble so no precipitate

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3
Q

How can ammonia solution distinguish between sliver nitrate precipitates

A

Add ammonia
AgCl - Soluble
AgBr - Soluble in excess
AgI - Insoluble

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4
Q

Why must silver nitrate be acidified when used to test halide ions

A

Prevents formation of silver carbonate
Forms from atmospheric CO2 dissolving in solution

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5
Q

Test for ammonium ions

A

Warm with NaOH solution. Produces basic gas NH3
Test with damp red litmus, turns blue
NH4+(aq) + OH-(aq) —> NH3(g) + H2O(l)

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6
Q

Test for carbonate ions

A

Add acid
Bubble gas produced in limewater
White precipitate formed from CO2, limewater turns cloudy

2H+(aq) + CO3^2-(aq) —> H2O(l) + CO2(g)

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7
Q

Test for hydroxide ions

A

Add Mg2+ solution
Forms white precipitate of Mg(OH)2

Mg2+(aq) + 2OH-(aq) —> Mg(OH)2(s)

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8
Q

Test for sulfate ions

A

Add acidified barium chloride solution. White pot of BaSO4 formed

Ba2+(aq) + SO4^2-(aq) —> BaSO4(s)

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9
Q

Why must barium chloride be acidified when testing for sulfate ions

A

Prevent formation of white ppt of baCO3
Formed when atmospheric CO2 dissolves in solution

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10
Q

Why do acidified barium chloride or acidified silver nitrate react with carbonate ions

A

Both solutions contain acid that reacts with the carbonate ions o produce CO2 gas

2H+(aq) + CO3^2-(aq) —> H2O(l) + CO2(g)

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11
Q

Give 2 sources of aqueous sulfate ions

A

Solutions of group 1 sulfate salts (Na2SO4 in solution produces SO4^2- (aq) ions)

Sulfuric acid (H2SO4 contains some SO4^2- ions)

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12
Q

What is the first step to test any unknown inorganic solid

A

Dissolve in water

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