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Chemistry > Ch12 Chemical analysis > Flashcards

Ch12 Chemical analysis Flashcards

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1
Q

pure susbtance

A

single element or compound not mixed with any other substance

melt and boil at specific temperatures(fixed points)

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2
Q

melting and boiling point data

A

used to identify a pure substance

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3
Q

Formulation

A

a mixture that has been designed to produce a useful product with required properties

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4
Q

examples of formulations

A

fuels, cleaning agents, paints, medicines, alloys, pesticides, fertilisers and
foods

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5
Q

Test for hydrogen

A

uses a burning splint held at the open end of a test tube of the gas
the hydrogen burns rapidly with a pop sound

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6
Q

Test for oxygen

A

glowing splint inserted into a test tub of the gas

the splint relights in oxygen

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7
Q

Test for carbon dioxide

A

uses an aqueous solution of calcium hydroxide(lime water)

when CO2 is shaken with or bubbled through limewater turns milky(cloudy)

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8
Q

Test for chorine

A

Damp blue litmus paper is put into the chlorine gas

The litmus paper is bleached and turns white

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9
Q

Lithium flame test

A

crimson

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10
Q

Sodium flame test

A

yellow

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11
Q

Potassium flame test

A

lilac

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12
Q

Calcium flame test

A

orange-red

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13
Q

Copper flame test

A

green

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14
Q

Flame test method

A
  1. A nichrome wire loop must be dipped into concentrated hydrochloric acid and then heated to clean it
  2. re-dipped into the acid before dipping it into the metal compound
  3. Hold the loop in the flame of a Bunsen burner
  4. Use the colour of them flame to identify the metal ion in the compound
  5. If the sample contains a mixture of metal ions, some flame colours can be masked
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15
Q

copper with sodium hydroxide

A

blue precipitate is formed

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16
Q

iron(II) with sodium hydroxide

A

green precipitate is formed

Fe2+(aq) + 2OH-(aq) –> Fe(OH)2(s)

17
Q

iron(III) with sodium hydroxide

A

brown precipitate is formed

18
Q

calcium with sodium hydroxide

A

white precipitate is formed

19
Q

magnesium with sodium hydroxide

A

white precipitate is formed

20
Q

aluminium with sodium hydroxide

A

white precipitate is formed
aluminium hydroxide precipitate dissolves in excess sodium hydroxide solution

Al3+(aq) + 3OH-(aq) –> Al(OH)3(s)

21
Q

test for carbonate ions

A

add dilute hydrochloric acid

bubbles are produced -carbon dioxide

CO3 2- + 2H+ –> CO2 + H2O

can be tested with limewater

22
Q

Test for halide ions

A

Add dilute nitric acid to the unknown compound
Then add silver nitrate solution
Positive for halide ions if a precipitate forms

23
Q

iodide ions with halide test

A

yellow precipitate

24
Q

bromide ions with halide test

A

cream precipitate

25
Q

chloride ions with halide test

A

white precipitate

26
Q

test for sulfate ions

A

add dilute hydrochloric acid to unknown compound to remove carbonate ions
then add barium chloride solution
Positive for sulphate ions if a white precipitate forms(barium sulphate)

Ba2+(aq) + SO42-(aq) –> BaSO4(s)

27
Q

Advantages for instrumental methods

A

highly accurate and sensitive
quicker
enable very small samples to be analysed

28
Q

Disadvantages for instrumental methods

A

very expensive
takes special training to use
gives results that can often be interpreted only by comparison with data from known substances

29
Q

Instrumental methods

A

used to detect and identify elements and compounds

30
Q

Flame emission spectroscopy

A

instrumental

method used to analyse what metal ions are in solutions and the concentration

31
Q

Method of flame emission spectroscopy

A
  1. solution is heated in a flame
  2. energy provided excites electrons in the metal ions, causing them to jump up energy levels
  3. when they fall back into low energy levels, energy is released as light energy, outputting a line spectrum
  4. line spectrum is used to identify the metal ion by comparing it on a computer database
  5. spectrometer can measure the intensity(absorbance) and wavelength of light to measure the concentration of the metal ions
32
Q

Mobile phase in chromatography

A

the chosen solvent moves through the stationary phase, carrying the components of the mixture under investigation

33
Q

Stationary phase in chromatography

A

the paper

34
Q

Rf value in chromatography

A

retention factor

distance moved by substance/ distance moved by solvent

helps identify the compounds

Chemistry (16 decks)

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