qualitative analysis Flashcards

1
Q

how can we identify the present cations in an unknown solution?

A

by adding aqueous sodium hydroxide or aqueous ammonia

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2
Q

what happens when NaOH(aq) is added to Zn2+?

A

white ppt, Zn(OH)2 is formed
precipitate dissolves in excess to give a colourless solution

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3
Q

what happens when NH3 is added to Zn2+?

A

white ppt, Zn(OH)2 formed
precipitate dissolves in excess to give a colourless solution

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4
Q

what happens when NaOH is added to Al3+?

A

white ppt, Al(OH)3 formed
precipitate dissolves in excess to give a colourless solution

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5
Q

what happens when NH3 is added to Al3+?

A

white ppt, Al(OH)3 formed
precipitate insoluble in excess

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6
Q

what happens when NaOH is added to Pb2+?

A

white ppt, Pb(OH)2 formed
precipitate dissolves in excess to give a colourless solution

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7
Q

what happens when NH3 is added to Pb2+?

A

white ppt, Pb(OH)2 formed
precipitate is insoluble in excess

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8
Q

what happens when NaOH is added to Ca2+?

A

white ppt, Ca(OH)2 formed
precipitate is insoluble in excess

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9
Q

what happens when NH3 is added to Ca2+?

A

no precipitate formed

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10
Q

what happens when NaOH is added to Cu2+?

A

light blue ppt, Cu(OH)2 formed
precipitate is insoluble in excess

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11
Q

what happens when NH3 is added to Cu2+?

A

light blue ppt, Cu(OH)2 formed
precipitate dissolves in excess to give a dark blue solution

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12
Q

what happens when NaOH is added to Fe2+?

A

green ppt, Fe(OH)2 formed
precipitate is insoluble in excess

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13
Q

what happens when NH3 is added to Fe2+?

A

green ppt, Fe(OH)2 is formed
precipitate is insoluble in excess

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14
Q

what happens when NaOH is added to NH4+?

A

no precipitate formed
when heated, ammonia gas is produced and moist red litmus paper turns blue

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15
Q

what happens when NH3 is added to NH4+?

A

no reaction

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16
Q

how to test for carbonate?

A

add dilue nitric acid
bubble gas into limewater

17
Q

what is observed when carbonate is present in test for carbonate?

A

acid will react with CO3^2- ions to produce carbon dioxide. effervesence is observed
white precipitate (CaCO3) will form in limewater
gas produced is carbon dioxide

18
Q

how to test for chloride?

A

add dilute nitric acid
then add silver nitrate solution

19
Q

what is observed if chloride is present in test for chloride?

A

white precipitate of silver chloride (AgCl) formed

20
Q

how to test for sulfate?

A

add dilute nitric acid
then add barium sulfate solution

21
Q

what is observed if sulfate is present in test for sulfate?

A

white precipitate of barium sulfate (BaSO4) formed

22
Q

how to test for nitrate?

A

add dilute sodium hydroxide
then add a piece of aluminum foil
warm the mixture
test the gas given off with a piece of moist red litmus paper

23
Q

what happens if nitrate is present in test for nitrate?

A

moist red litmus paper turns blue
gas produced is ammonia gas

24
Q

what are the properties of hydrogen and how to test for it?

A

-colourless and odourless
-place a lighted splint at the mouth of the test tube

25
Q

how to tell if hydrogen is present?

A

a ‘pop’ sound is extinguished by the lighted splint

26
Q

what are the properties of oxygen and how to test for it?

A

-colourless and odourless
-place a glowing splint into the test tube

27
Q

how to tell if oxygen is present?

A

the flame on the glowing splint reklindles

28
Q

what are the properties of carbon dioxide and how to test for it?

A

-colourless and odourless
-bubble gas through limewater

29
Q

how to tell if carbon dioxide is present?

A

white precipitate (CaCO3) is formed in limewater

30
Q

what are the properties for chlorine and how to test for it?

A

-greenish-yellow gas with a pungent sme;;
-place a piece of moist blue litmus paper at the mouth of the test tube

31
Q

how to tell is chlorine is present?

A

moist blue litmus paper turns red and then bleached (white)

32
Q

what are the properties of sulfur dioxide and how to test for it?

A

-colourless gas with a pungent smell
-place a piece of filter paper soaked with acidified potassum manganate(VII) at the mouth of the test tube

33
Q

how to tell if sulfur dioxide is present?

A

purple acidified potassium manganate turns colourless
(SO2 is a reducing agent)

34
Q

what are the properties of ammonia and how to test for it?

A

-colourless gas with a pungent smell
-place a piece of moist red litmus paper at the mouth of the test tube

35
Q

how to tell if ammonia is present?

A

moist red litmus paper turns blue