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GCE O'Levels Chemistry > Qualitative Analysis > Flashcards

Qualitative Analysis Flashcards

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1
Q

What are the cations that we can test for?

A

Aluminium, calcium, lead, zinc (white ppts),
copper (II) (blue ppt),
iron (II) (green ppt),
iron (III) (reddish brown ppt) and
ammonium (testing for alkaline gas).

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2
Q

What are the 2 solutions used for testing cations?

A

Sodium hydroxide (NaOH) and aqueous ammonia (NH3).

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3
Q

For aluminium (Al3+), what is the effects of positive test with sodium hydroxide?

A

Upon adding a few drops, white ppt is produced. The white ppt is Al(OH)3.
Cation is soluble in excess, producing a colourless solution.

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4
Q

For aluminium (Al3+), what is the effects of positive test with aqueous ammonia?

A

Upon adding a few drops, white ppt is produced. The white ppt is Al(OH)3.
Cation is insoluble in excess, white ppt remains.

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5
Q

For calcium (Ca2+), what is the effects of positive test with sodium hydroxide?

A

Upon adding a few drops, white ppt is produced. The white ppt is Ca(OH)2.
Cation is insoluble in excess, white ppt remains.

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6
Q

For calcium (Ca2+), what is the effects of positive test with aqueous ammonia?

A

Cation is soluble in aqueous ammonia, producing a colourless solution.

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7
Q

For lead (Pb2+), what is the effects of positive test with sodium hydroxide?

A

Upon adding a few drops, white ppt is produced. The white ppt is Pb(OH)2.
Cation is soluble in excess, producing a colourless solution.

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8
Q

For lead (Pb2+), what is the effects of positive test with aqueous ammonia?

A

Upon adding a few drops, white ppt is produced. The white ppt is Pb(OH)2.
Cation is insoluble in excess, white ppt remains.

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9
Q

For zinc (Zn2+), what is the effects of positive test with sodium hydroxide?

A

Upon adding a few drops, white ppt is produced. The white ppt is Zn(OH)2.
Cation is soluble in excess, producing a colourless solution.

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10
Q

For zinc (Zn2+), what is the effects of positive test with aqueous ammonia?

A

Upon adding a few drops, white ppt is produced. The white ppt is Zn(OH)2.
Cation is soluble in excess, producing a colourless solution.

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11
Q

On both tests with sodium hydroxide and aqueous ammonia, aluminium and lead (II) ions produce the same results. What test can be conducted to differentiate the two cations?

A

Add a solution containing chloride (eg. aqueous sodium chloride) to each of the solutions (one containing Al3+ and the other Pb2+).
Al3+ is soluble in chloride-containing solutions, producing colourless solution.
Pb2+ is insoluble in chloride-containing solutions, producing a white ppt (lead (II) chloride, PbCl2).

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12
Q

For copper (II) (Cu2+), what is the effects of positive test with sodium hydroxide?

A

Upon adding a few drops, light blue ppt is produced. The light blue ppt is Cu(OH)2.
Cation is insoluble in excess, light blue ppt remains.

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13
Q

For copper (II) (Cu2+), what is the effects of positive test with aqueous ammonia?

A

Upon adding a few drops, light blue ppt is produced. The light blue ppt is Cu(OH)2.
Cation is soluble in excess, producing a dark blue solution.

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14
Q

For iron (II) (Fe2+), what is the effects of positive test with sodium hydroxide?

A

Upon adding a few drops, green ppt is produced. The green ppt is Fe(OH)2.
Cation is insoluble in excess, green ppt remains.

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15
Q

For iron (II) (Fe2+), what is the effects of positive test with aqueous ammonia?

A

Upon adding a few drops, green ppt is produced. The green ppt is Fe(OH)2.
Cation is insoluble in excess, green ppt remains.

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16
Q

For iron (III) (Fe3+), what is the effects of positive test with sodium hydroxide?

A

Upon adding a few drops, reddish brown ppt is produced. The reddish brown ppt is Fe(OH)3.
Cation is insoluble in excess, reddish brown ppt remains.

17
Q

For iron (III) (Fe3+), what is the effects of positive test with aqueous ammonia?

A

Upon adding a few drops, reddish brown ppt is produced. The reddish brown ppt is Fe(OH)3.
Cation is insoluble in excess, reddish brown ppt remains.

18
Q

What are the anions we can test for?

A

Carbonate (CO3 ^2-)
Nitrate (NO3 ^-)
Sulfate (SO4 ^2-)
Chloride (Cl-)
Iodide (I-)

19
Q

What is the test for carbonate (CO3 ^2-) anions? And what are the observations for positive test?

A

Test: to add dilute hydrochloric acid (HCl)
Positive test’s observation: Effervescence is observed. The gas produced is carbon dioxide (CO2). To test for identity of carbon dioxide, bubble gas produced into limewater. Upon positive test, white ppt is observed in the limewater.

20
Q

What is the test for nitrate (NO3 ^-) anions? And what are the observations for positive test?

A

Test: to add aqueous sodium hydroxide, then aluminium foil. Warm mixture gently.
Positive test’s observation: A pungent smell will be observed. The gas produced is ammonia (NH3).
To test for identity of ammonia, use a moist res litmus paper and put it at the mouth of the test tube. Upon positive test, moist red litmus paper turns blue.

21
Q

What is the test for sulfate (SO4 ^2-) anions? And what are the observations for positive test?

A

Test: to add dilute nitric acid (HNO3), then add aqueous barium nitrate.
Positive test’s observation: A white ppt is observed.

22
Q

What is the test for chloride (Cl ^-) anions? And what are the observations for positive test?

A

Test: To add dilute nitric acid (HNO3), then add aqueous silver nitrate.
Positive test’s observation: A white ppt is observed.

23
Q

What is the test for iodide (I ^-) anions? And what are the observations for positive test?

A

Test: To add dilute nitric acid (HNO3), then add aqueous silver nitrate.
Positive test’s observation: A yellow ppt is observed.

24
Q

What are the gases we can test for?

A

Ammonia (NH3)
Carbon dioxide (CO2)
Chlorine (Cl2)
Hydrogen (H2)
Oxygen (O2)
Sulfur dioxide (SO2)

25
Q

What is the test for ammonia gas? And what are the observations for positive test?

A

Test: using moist red litmus paper
Positive test observation: moist red litmus paper turns blue.

26
Q

What is the test for carbon dioxide gas? And what are the observations for positive test?

A

Test: to bubble gas into a test tube of limewater
Positive test observation: a white ppt is observed to form in the limewater.

27
Q

What is the test for chlorine gas? And what are the observations for positive test?

A

Test: using moist litmus paper (don’t matter if red or blue)
Positive test observation: litmus paper becomes bleached (loses the original colour)

28
Q

What is the test for hydrogen gas? And what are the observations for positive test?

A

Test: using a lighted splint (you can see the flame on the splint), and bring it to the mouth of the test tube.
Positive test observation: the lighted splint extinguishes with a ‘pop’ sound.

29
Q

What is the test for oxygen gas? And what are the observations for positive test?

A

Test: using a glowing splint (you cannot see the flame, but is glowing red on the splint), and bring it to the mouth of the test tube.
Positive test observation: glowing splint will rekindle (now can see the flame).

30
Q

What is the test for sulfur dioxide gas? And what are the observations for positive test?

A

Test: add acidified aqueous potassium manganate (VII) –> purple solution.
Positive test observation: Purple acidified aqueous potassium manganate (VII) will turn colourless.

GCE O'Levels Chemistry (6 decks)

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