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Chemistry > 4.6 Chemical Analysis > Flashcards

4.6 Chemical Analysis Flashcards

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1
Q

Test for hydrogen?

A

SQUEAKY POP TEST
METHOD: 1. Collect a sample of gas in a test tube
2. Attempt to ignite the gas using a lit splint.
RESULT: Squeaky pop sound
-Combustion of H2
-Sound caused by hot gas rushing out of test tube

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2
Q

Test for oxygen?

A

GLOWING SPLINT TEST
METHOD: 1. Collect a sample of gas in a test tube
2. Place a glowing splint into the tube
RESULT: The splint relights
-Combustion of wood in the splint
-Relights because pure O2 is more concentrated than the 02 in normal air
-Wood in splint combusts faster

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3
Q

Test for water? For the presence of H20

A

COPPER SULFATE TEST
METHOD: 1. Add anhydrous copper sulfate
RESULT: Changes from white —>blue

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4
Q

Test for water? For purity of H20

A

MEASURE ITS BOILING POINT & COMPARE IT TO 100C
METHOD: 1. Measure its boiling point
RESULT: Closer to 100c = more pure

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5
Q

Test for Carbon Dioxide?

A

LIMEWATER TEST
METHOD: 1. Bubble a sample of gas through limewater
RESULT: White precipitate forms (turns cloudy)
-Limewater=saturated calcium hydroxide
-Forms white ppt of calcium carbonate when it reacts with CO2

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6
Q

Test for chlorine?

A

DAMP BLUE LITMUS TEST
METHOD: 1. Place damp blue litmus paper in a sample of gas
RESULT: Turns white (bleaches)
-Cl2= good bleaching agent

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7
Q

Test for ammonia?

A

DAMP RED LITMUS TEST
METHOD: 1. Place damp red litmus paper in a sample of gas
RESULT: Turns blue

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8
Q

What are cations?

A

-Positive Ions
Li (+), Na (+), K (+), Ca (2+), Cu (2+), Fe (2+), Fe (3+), NH4 (+)

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9
Q

What type of flame is used in a flame test?

A

Non luminous (blue) Bunsen flame

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10
Q

How do you conduct a flame test?

A
  1. -Dip a piece of nichrome/ platinum wire into HCL
    -These wires don’t colour the flame & the acid cleans the wire
  2. -Dip the wire into a sample of solid or solution
    -This causes some of the sample to stick onto the wire
  3. -Place the tip of the wire into a non-luminous Bunsen flame
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11
Q

Red Flame (metal cation)

A

Li+

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12
Q

Yellow (metal cation)

A

Na+

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13
Q

Lilac flame (metal cation)

A

K+

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14
Q

Orange-red Flame (metal cation)

A

Ca2+

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15
Q

Blue-green flame (metal cation)

A

Cu2+

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16
Q

Blue-green flame (metal cation)

A

Cu2+

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17
Q

What do we use sodium hydroxide (NaOH) to test for?

A

Cu2+, Fe2+, Fe3+

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18
Q

How do you conduct a sodium hydroxide test?

A
  1. Dissolve the sample in water
  2. Add a free drops of NaOH(aq)
19
Q

What are the results for the sodium hydroxide test? Ppt colour, ppt formula & Metal cation

A

Blue- Cu(OH)2- Cu2+
Green- Fe(OH)2- Fe2+
Brown- Fe(OH)3- Fe3+

20
Q

Write an ionic equation that shows the formation of the ppt (Cu2+)

A

Cu2+(aq) + 2OH- (aq) —> Cu(OH)2(s)

21
Q

What is used to test for ammonium (NH4+) ions?

A

Sodium hydroxide (NaOH)

22
Q

How do you conduct an Ammonium Test?

A
  1. Dissolve the sample in water
  2. Add some NaOH(aq) & warm it
  3. Test the gas evolved with damp red litmus paper i.e. The Ammonia Test
23
Q

If NH4+ ions are present in the original sample, the litmus paper will turn…

A

Blue

24
Q

What is the balanced equation for the ammonium test?

A

NH4+ (aq) (sample containing NH4+) + OH-(aq) —> NH3(g) (test with damp red litmus paper) + H2O(l)

25
Q

What are anions?

A

-Negative ions
Cl (-), Br (-), I (-), CO3 (2-), SO4 (2-)

26
Q

What are the halide ions? And what is the test called?

A

Cl-, Br-, I-
-Silver Nitrate Test

27
Q

How do you conduct a test for halide ions?

A
  1. Dissolve the sample in water
  2. Add nitric acid (HNO3)
  3. Add silver nitrate (AgNO3)
28
Q

What are the results for the silver nitrate test? Ppt colour, ppt formula & halide ion

A

White- AgCl- Cl-
Cream- AgBr- Br-
Yellow- AgI- I-

29
Q

What is the ionic equation for silver chloride? (silver nitrate test)

A

Ag+(aq) + Cl-(aq) —> AgCl(s)

30
Q

How do you conduct a test for carbonate ions (anions)?

A
  1. Add HCL to sample , look for effervescence
  2. If there is effervescence, bubble the gas through limewater
31
Q

If CO3 (2-) ions were present in the sample, the gas evolved turns the limewater….

A

Cloudy

32
Q

What is the reaction equation if we test calcium carbonate (CaCO3) for carbonate ions?

A

CaCO3(s) Sample containing CO3 (2-) + 2HCL(aq) —-> CaCl2(aq) + H2O (l) + CO2 (g) Test using limewater

33
Q

How do you conduct a test for sulfate ions (anions)?

A
  1. Add HCL to the sample, look for effervescence
  2. If theres no effervescence, add barium chloride (BaCl2) solution
34
Q

If SO4 (2-) ions are present, they will form a _________

A

White precipitate

35
Q

Why is it important to add the HCL in step one of a sulfate ion test?

A

Carbonate ions also form a white ppt with Ba2+ ions
(By only continuing to step 2 if there’s no effervescence, we can prevent a false positive)

36
Q

Why is it important to add HNO3 in step 2 of the silver nitrate test?

A

Ag+ ions also form ppts with other anions (OH- & CO3 2-)
-HNO3 reacts with those anions, preventing false positives

37
Q

What is chromatography?

A

A method of separating mixtures- usually mixtures of dyes in inks, paints, food colourings etc.

38
Q

How to do paper chromatography:

A
  1. Draw a line near the bottom of the chromatography paper in pencil (The pencil is insoluble so will not dissolve in the solvent)
  2. Add spots of the different dyes to the line at regular intervals
  3. Place the paper into a beaker of solvent (Make sure the solvent is below the pencil line- otherwise the inks will dissolve into the solvent)
  4. Place a lid on the beaker (To stop the solvent evaporating)
  5. Allow the solvent to move up the paper until it is just below the top
  6. Take the paper out and mark on where the solvent has reached (This is called the solvent front)
  7. Allow the paper to dry
39
Q

The more soluble the dye in the solvent…

A

The further up the paper it will go

40
Q

If the dye is insoluble it will…

A

Not move from the baseline

41
Q

If the dye is insoluble it will…

A

Not move from the baseline

42
Q

How do you know if a dye contains another dye?

A

If the spot has risen to the same point

43
Q

Rf value

A

Rf= distance moved by spot/ distance moved by solvent

Chemistry (12 decks)

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