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Chemistry > chemical analysis > Flashcards

chemical analysis Flashcards

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1
Q

what is a pure substance

A

a substance which is made up of one substance which is either an element or a compound

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2
Q

how do you test if water is present

A

the substance turns white anhydrous copper sulphate blue

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3
Q

how do you test for pure water

A

the melting point of pure water is exactly 0 and boiling point is exactly 100

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4
Q

what will happen to the melting point of a mixture

A

it will not be fixed and will vary. it will have changes of state over a variety of temperatures

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5
Q

what do impurities do to boiling and melting points of substances

A

lower the melting point and raise the boiling point

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6
Q

what is a formulation

A

a mixture which has been designed to produce a useful product

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7
Q

2 examples of formulations

A

fuels, alloys

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8
Q

what are the two phases involved in chromatography

A

the mobile phase and the stationary phase

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9
Q

what can chromatography be used for

A

to separate and identify mixtures of amino acids

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10
Q

what will differ between each component in a mixture

A

each component will have a different attraction to the mobile and stationary phase

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11
Q

what will happen to a component which has a stronger force of attraction to the mobile phase than the stationary phase

A

the component will travel a greater distance

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12
Q

what will happen to a component with a stronger force of attraction to the stationary phase than the mobile phase

A

it will not travel as far

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13
Q

what does multiple dots on a chromatography sheet suggest about the component

A

it is a mixture

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14
Q

how do you calculate retention factor

A

distance moved by substance/distance moved by solvent

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15
Q

what is the test for hydrogen

A

a lighted splint pops

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16
Q

test for oxygen

A

a glowing splint relights

17
Q

test for carbon dioxide

A

limewater turns milky / cloudy white

18
Q

test for chlorine

A

damp blue litmus paper turns white

19
Q

what is used to identify positive ions

A

sodium hydroxide

20
Q

what precipitates form when aluminium, magnesium and calcium ions are mixed with sodium hydroxide

A

white precipitates

21
Q

what is the ionic equation for the reaction with aluminium ions

A

Al3+ + 3OH- —> Al(OH)3

22
Q

Copper + sodium hydroxide = ?

A

blue precipirate

23
Q

iron (II) + sodium hydroxide = ?

A

green precipitate

24
Q

iron (III) + sodium hydroxide = ?

A

brown precipirate

25
Q

Lithium in a flame = ?

A

crimson

26
Q

sodium in a flame = ?

A

yellow

27
Q

potassium in a flame = ?

A

lilac

28
Q

calcium in a flame = ?

A

orange-red

29
Q

copper in a flame = ?

A

green

30
Q

what should be used to hold the acid while performing a flame test and how do you clean it

A

a nichrome wire loop should be used.
it should be dipped in hydrochloric acid and then heated and then dipped in the hydrochloric acid again to clean it before dipping it in the metal compound

31
Q

why might a flame be two different colours

A

because it is a mixture

32
Q

how do you identify carbonates

A

if you add the suspected carbonate to dilute hydrochloric acid it fizzes and produces carbon dioxide. If the gas produced forms a white/cloudy precipitate in lime water it is a carbonate

33
Q

what would you use to test for halides

A

dilute nitric acid and then silver nitrate. The dilute nitric acid would dissolve the compound and remove any carbonate ions. The silver nitrate would cause the colour change

34
Q

iodide ions + silver nitrate = ?

A

yellow precipitate

35
Q

bromide ions + silver nitrate = ?

A

cream precipitate

36
Q

chloride ions + silver nitrate = ?

A

white precipitate

37
Q

what do you use to test for sulphates

A

dilute hydrochloric acid and then barium chloride solution. the barium solution will turn the solution a white precipitate.

38
Q

what is flame emission spectroscopy

A
  • a sample is heated in a flame
  • the energy excites electrons in the metal ions causing the to jump from electron shells
  • when the electrons return to their energy levels when they cool, light energy is emitted
  • the spectrometer analyses the wavelengths produced which can then be identified to find out what metal ion is present
  • the spectrometer can also measure the intensity of the wavelength which indicates the concentration

Chemistry (12 decks)

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