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Chemistry > Chemical Analysis > Flashcards

Chemical Analysis Flashcards

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1
Q

what is a pure substance

A

a pure substance only contains one element or compound

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2
Q

what is the link between pure substances and melting and boiling points

A

pure elements and compounds melt and boil at specific temperatures so their data can be used to distinguish pure substances

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3
Q

what is an impure substance

A

a mixture of elements and compounds

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4
Q

examples of pure substances

A

copper
aluminium
sodium chloride

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5
Q

examples of impure substances

A

milk
beer
water

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6
Q

melting and boiling points in impure substances

A

do not have a specific melting point , they have a range

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7
Q

what is a formulation

A

a mixture that has been designed as a useful product

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8
Q

how are formulations made

A

by mixing the components in carefully measured quantities to ensure that the product has the required properties

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9
Q

examples of formulations

A

fuels
cleaning agents
paints
medicines
alloys
fertilisers
foods

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10
Q

what are many products of formulations

A

complex mixtures in which each chemical has a particular purpose

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11
Q

what is the purpose of chromatography

A

to separate mixtures and give information to help identify substances

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12
Q

what does chromatography involve

A

a stationary phase and a mobile phase

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13
Q

what is the stationary phase in chromotography

A

chromatography paper

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14
Q

what is the mobile phase in chromotography

A

solvent

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15
Q

how does paper chromotography separate compounds

A

separates compounds by their relative speeds in a solvent as it spreads through paper

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16
Q

how does chromatography show how soluble a substance is

A

it will travel further up the paper

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17
Q

what is the solvent front

A

the distance travelled by the solvent

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18
Q

why does the start line have to be in pencil

A

if it is drawn in ink the ink line will run/smudge up the paper

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19
Q

why does the pencil line have to be above the water surface

A

the colouring spots will dissolve into the water instead of rising up the paper

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20
Q

how to structure exam question eg
write a conclusion about the black ink in the experiment (4)

A
  • how many substances are in it
  • what substances are in it
  • what substances are not in it
  • anything else
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21
Q

how to calculate rf value

A

distance moved by the spot / distance moved by the solvent

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22
Q

what does it mean if two substances have the same rf value

A

they are the same substance

23
Q

what is the test for hydrogen

A

use a burning splint held at the open end of a test tube of the gas
creates a squeaky pop sound as hydrogen burns rapidly

24
Q

what is the test for oxygen

A

a glowing splint inserted into a test tube of the gas
splint relights in oxygen

25
Q

what is the test for carbon dioxide

A

bubble the gas through limewater (calcium hydroxide)
turns milky/cloudy

26
Q

test for chlorine

A

damp blue litmus paper into gas
bleaches the litmus paper so it turns white

27
Q

method for flame test

A
  1. pour 1cm^3 of each known chloride solution into 5 test tubes
  2. clean the nichrome wire by dipping it in dilute hydrochloride acid
  3. dip the nichrome wire into solution and hold the tip in a blue bunsen flame
  4. record the colour of the flame
  5. repeat for the other solutions and clean the wire after each test
    6, pour 1cm^3 of the unknown salt solution into test tube
  6. dip the nichrome wire into the solution and hold the tip in a blue bunsen flame
  7. record the colour of the flame and compare results with known chloride and matching colour flame
28
Q

what colour shows lithium ions are present in the flame test

A

crimson flame

29
Q

what colour shows that sodium ions are present in the flame test

A

yellow flame

30
Q

what colour shows potassium ions are present in the flame test

A

lilac flame

31
Q

what colour flame shows calcium ions are present in the flame test

A

orange/red flame

32
Q

what colour flame shows copper 11 is present in the flame test

A

green flame

33
Q

Carbonate ion test method

A
  1. place 2cm^3 of limewater in a clean test tube
  2. add a little dilute HCl to the unknown solution
  3. if bubbles are present transfer the gas produced to the limewater using a delivery tube
  4. repeat this process for the known sodium solutions to identify carbonate ions
34
Q

what is the result for the carbonate ion test

A

bubbles produced and limewater goes cloudy if present

35
Q

method for sulphate ion test

A
  1. add 10 drops of dilute HCl to the unknown solution in a test tube
  2. add 2cm^3 of barium chloride solution
  3. pour 1cm^3 of the known sodium solutions into separate test tubes
  4. add 5 drops of dilute HCl and then 2cm^3 of barium chloride
36
Q

result of sulphate ion test

A

white precipitate formed (BaSo4) if sulphate ions present

37
Q

method for halide ion test

A
  1. add 10 drops of dilute nitric acid to unknown solution in a test tube
    2 add 1cm^3 silver nitrate soliutuoon to tets tube with the unknown solution
  2. pour 1cm^3 of the known sodium solutions into separate test tubes
  3. repeat steps 1 and 2 for each solution
  4. record colour of precipitate formed in each test tube
38
Q

result of halide ion test

A

precipitate formed

39
Q

result of chloride ion in halide test

A

white precipitate

40
Q

result of bromide ion in halide test

A

cream precipitate

41
Q

result of iodide ion present in halide test

A

yellow precipitate formed

42
Q

what is the limitation of flame tests

A

if a sample containing a mixture of ions is used some flame colours can be masked

43
Q

which ions form white precipitates in the sodium hydroxide test

A

aluminium
magnesium
calcium

44
Q

what is the white precipitate in the sodium hydroxide test

A

an insoluble metal hydroxide

45
Q

what happens if you add excess NaOH to the white precipitates formed in the sodium hydroxide test

A

only aluminiums precipitate will redissolve

46
Q

which metals produce a coloured compound in the sodium hyroxide test

A

copper II
iron II
iron III

47
Q

what is formed when copper II is added to sodium hydroxide solution

A

pale blue precipitate Cu(OH)2

48
Q

what is formed when Fe II is added to sodium hydroxide solution

A

dirty green precipitate Fe(OH)2

49
Q

what is formed when iron III is added to sodium hydroxide solution

A

rusty brown precipitate Fe(OH)3

50
Q

acronym for halide test results

A

cats with brains can ideally yodel

51
Q

what can instrumental methods be used to detect

A

elements and compounds

52
Q

advantages of instrumental methods compared to chemical tests

A

accurate
sensitive
rapid

53
Q

process of flame emission spectroscopy

A

sample is put into a flame and the light given out is passed through a spectroscope
the output it a line spectrum that can be analysed to identify the metal ions in the solution and measure their concentrations

54
Q

disadvantages of atomic emission spectroscopy

A

destructive as the sample being tested is burned
only identifies the prescence of elements not compounds

Chemistry (36 decks)

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