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Science > Qualitive Analysis > Flashcards

Qualitive Analysis Flashcards

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1
Q

What are flame tests used for?

A

To identify metal ions in substances

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2
Q

How to carry out a flame test?

A
  • Light Bunsen Burner and open air hole to give hot blue flame
  • Pick up small smaple using wire loop
  • Hold sample in edge of flame and observe and record flame colour
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3
Q

What is used to clean the wire loop?

A

Hydrochloric acid

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4
Q

Why is platinum used for the wire loop?

A

Has a high melting point, is unreactive and gives no colour to the flame

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5
Q

What is normally used instead of platinum for the wire loop?

A

Nichrome alloy because although it produces faint orange colour in flame, it is much cheaper

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6
Q

What are the different colours produced by these different cations?…

  • Lithium
  • Sodium
  • Potassium
  • Calcium
  • Copper
  • Iron (II)
  • Iron (III)
A 
Li+ = red
Na+ = yellow
K+ = lilac
Ca2+ = orange-red
Cu2+ = blue-green
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7
Q

What can photometry do better than simple flame tests?

A
  • Better sensitivity (detect much smaller amounts)
  • Accuracy (give values closer to true values)
  • Speed (gives results faster)
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8
Q

What does a flame photometer measure?

A

Light intensity of the flame colours produced by metal ions

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9
Q

What does flame photometry produce?

A

A calibration curve produced using different standard solutions, each containing known concentrations of the metal ion dissolved in distilled water

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10
Q

What does a spectrum produced by a flame photometer show?

A

Since the colours produced are usually a mixture, the spectrum separates them out to detect which metal ion is is in the solution as different metal ions produce different emission spectra

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11
Q

How is a hydroxide precipitate produced?

A
  • Sample solution placed in test tube

- Few drops of dilute sodium hydroxide solution are added

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12
Q

What hydroxide precipitates are produced by copper, iron (II) and iron (III)?

A 
Cu2+ = blue
Fe2+ = green
Fe3+ = brown
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13
Q

How is a precipiate formed since sodium hydroxide is soluble in water?

A

Most hydroxides are insoluble and so form precipitates in these tests

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14
Q

How do you treat water that flows through mines and contaminates rivers?

A

React the metals with sodium hydroxide which will produce a precipitate which will settle out and can be removed

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15
Q

What colour precipitate does aluminium and calcium produce?

A

White

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16
Q

How can you distinguish between aluminium and calcium?

A

Do a further test - aluminium hydroxide disappears to form a colourless solution when excess sodium hydroxide is added, but calcium hydroxide does not

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17
Q

How do you test for ammonium ions?

A
  • Add dilute sodium hydroxide solution to ammonium ions solution
  • Ammonia gas is produced when ammonium ions mixture is warmed
  • Ammonia has characteristic sharp smell but confirmatory test is used to identify it
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18
Q

What is the confirmatory test for ammonia?

A

Damp red litmus paper changes to blue when ammonia is present

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19
Q

Describe the test to identify metal ions in a solution using dilute sodium hydroxidde solution

A
  • Using a dropping pipette, fill a test tube to depth of 2cm with solution
  • Using different dropping pipette, add few drops of dilute sodium hydroxide solution to the tube
  • Gently shake tube
  • Observe and record colour
  • If white do further test to distinguish between aluminium hydroxide and calcium hydroxide
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20
Q

How do you test for carbonate ions?

A
  • Add dilute hydrochloric acid to the test substance
  • Look for effervescence of CO2
  • Carry out CO2 confirmatory test (bubble gas through limewater and should turn milky)
21
Q

Why should you use dilute hydrochloric acid as opposed to concentrated?

A
  • Less expensive

- Less damaging to the environment

22
Q

How do you test for sulfate ions?

A
  • Add few drops of dilute hydrochloric acid which acidifies the solution and removes carbonate ions that might give a precipitate in the test
  • Add a few drops of barium chloride solution
  • White precipitate of barium sulfate forms if the sample contains sulfate ions
23
Q

Where do halide ions come from?

A

Group 7 halogens form compounds containing halide ions

24
Q

Which silver halide is soluble unlike all others while are insoluble?

A

Silver fluoride

25
Q

How do you test for halide ions?

A
  • Add a few drops of dilute nitric acid which acidifies the solution and removes carbonate ions that might also give a precipitate in the test
  • Add a few drops of silver nitrate solution
  • Observe and record the colour
26
Q

What are the colours for the precipitates formed in these halide ions?…

  • Chloride
  • Bromide
  • Iodide
A 
Cl- = white
Br- = cream
I- = yellow
27
Q

What is a composite material?

A

A mixture of two or more materials combined together, each with different properties

28
Q

What is the difference between a reinforcement material and matrix material in a composite material?

A
  • Reinforcement = discontinuous phase

- Matrix - continuous phase

29
Q

What is tensile strength?

A

Resistance to being stretched

30
Q

What is compressive strength?

A

Resistance to being squashed

31
Q

What is a laminate?

A

A material that is stronger along its grain than across its grain

32
Q

What are ceramics?

A

Materials that are a range of durable compounds that change very little when heated

33
Q

Describe common properties of ceramics

A
  • Unreactive
  • Hard
  • Stiff
  • Brittle
  • Poor electrical and thermal conductors
  • High melting points
  • Giant structures with many strong covalent/ionic bonds
34
Q

How are clay ceramics like brick, porcelain, and china made?

A
  • Clay is moulded into desired shape
  • Heated to very high temperatures and crystals form and join together
  • Bricks usually decorated by adding coloured substance to clay before heating
  • Porcelain and china dipped in ‘glaze’ and heated strongly again, forming hard, waterproof, smooth surface you see on tiles, washbasins and toilet bowls
35
Q

How is glass made?

A

Melting sand, then allowing it to cool and solidify

36
Q

How is glass and clay ceramics different?

A

Atoms in glass are not arranged in a regular way to form crystals, so glass is transparent rather than opaque

37
Q

Describe how modern window glass is made by the float process

A
  • Molten glass is poured onto a bath of molten tin, where it spreads out on the surface
  • Flat layer of glass is drawn away and cooled in a continuous process
38
Q

Describe some properties of polymers

A
  • Very high relative formula masses
  • Strong
  • Chemically unreactive
  • Poor electrical and thermal conductors
39
Q

Give some uses for these materials…

  • Glass ceramics
  • Clay ceramics
  • Polymers
  • Metals
A

Glass ceramics = window glass, bottles
Clay ceramics - bricks, china, porcelain
Polymers = bottles, crates, carrier bags
Metals = cars, bridges, electrical cables

40
Q

What is the difference between transparent, translucent and opaque?

A 
Transparent = clear and fully see-through
Translucent = lets light through but not detailed shapes
Opaque = does not let light through
41
Q

Why are lumps and powders examples of bulk materials?

A

They contain a huge number of atoms

42
Q

How small are nanoparticles?

A

1-100nm

43
Q

Are atoms or nanoparticles larger?

A

Nanoparticles, but they are smaller than cells

44
Q

What are nanoparticulate materials?

A

They are substances that consist of nanoparticles; they occur naturally, but modern applications involve manufacturing them

45
Q

What do the uses of nanoparticulate materials depend on?

A
  • The small size of the nanoparticles

- Their large surface area to volume ratios

46
Q

Describe the use of titanium dioxide, a nanoparticulate material

A
  • In bulk it is a white solid
  • Absorbs harmful UV radiation from sun which could cause skin cancer
  • It is transparent because its particles are very small
  • Almost-invisible sunscreen
47
Q

What does the very large SA:V ratio mean for nanoparticles?

A

Makes them useful as catalysts

48
Q

How do stain-resistant clothes treated with nanoparticulate materials stay clean?

A

The nanoparticles catalyse the breakdown of dirt

49
Q

Why do some scientists think nanoparticulate materials pose a hazard to humans and the environment?

A
  • Small size means can be breathed in or pass through cell-surface membranes
  • Large SA:V ratios may allow them to catalyse harmful reactions or carry toxic substances bound to their surfaces

Science (23 decks)

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