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Chemistry > C8-Chemical Analysis > Flashcards

C8-Chemical Analysis Flashcards

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1
Q

What are pure substances?

A

Compounds or elements that contain only one substance

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2
Q

How can we test if a substance is pure?

A

The melting and boiling points of an elements are at specific temperatures

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3
Q

What is a formulation?

A

A mixture that has been designed to produce a useful product

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4
Q

Why do some substances move further along a chromatogram than others?

A

They have a stronger force of attraction between itself and the mobile phase relative to the stationary phase.

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5
Q

What does Rf stand for?

A

Retention factor

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6
Q

How do you calculate Rf values?

A

Distance travelled by substrate/distance travelled by solvent

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7
Q

What tube is used to drop substances onto chromotography paper?

A

Capillary

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8
Q

How is hydrogen gas tested and what is the positive result?

A
  • Holding a lit splint at the open end
  • A squeaky ‘pop’ sound
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9
Q

How is oxygen gas tested and what is the positive result?

A
  • Insert glowing splint into flask (made from blowing out splint)
  • The splint relights
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10
Q

How is carbon dioxide gas tested and what is the positive result?-2 methods

A
  • Bubble carbon dioxide through limewater using a delivery tube
  • Limewater turns cloudy
    or
  • Hold a lit splint at open end
  • Splint extinguishes
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11
Q

How is chlorine gas tested and what is the positive result?

A
  • Hold damp blue litmus paper at top of boiling tube
  • Damp blue litmus paper turns red then white (bleaches)
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12
Q

How is a metal flame test carried out?

A
  • A nichrome wire loop should be dipped in concentrated hydrochloric acid, heated and dipped in acid again before dipping it into the metal compound that is being tested
  • The loop us then held over the roaring blue flame of a Bunsen burner
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13
Q

What colour does the flame test for lithium produce?

A

Crimson

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14
Q

What colour does the flame test for sodium produce?

A

Yellow

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15
Q

What colour does the flame test for potassium produce?

A

Lilac

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16
Q

What colour does the flame test for calcium produce?

A

Orange-red

17
Q

What colour does the flame test for copper produce?

A

Green

18
Q

When a metal ion is combined with sodium hydroxide what is formed?

A

A precipitate

19
Q

What colour precipitate is formed when adding sodium hydroxide to copper (II) ions?

A

Blue

20
Q

What colour precipitate is formed when adding sodium hydroxide to iron (II) ions?

A

Green

21
Q

What colour precipitate is formed when adding sodium hydroxide to iron (III) ions?

A

Brown

22
Q

What colour precipitate is formed when adding sodium hydroxide to Al³⁺ ions?

A

White

23
Q

What colour precipitate is formed when adding sodium hydroxide to Ca²⁺ ions?

A

White

24
Q

What colour precipitate is formed when adding sodium hydroxide to Mg²⁺ ions?

A

White

25
Q

How can we tell apart aluminium ions from magnesium or calcium irons?

A

Aluminium ions dissolve

26
Q

How can we tell apart calcium ions from magnesium ions

A

Calcium ions produce an orange-red flame when burnt. Magnesium ions dont produce a flame when burnt.

27
Q

What are the tests for carbonates?

A

Add a dilute acid to a carbonate and it produces carbon dioxide gas (effervesced)-turns limewater milky

28
Q

What is the test for sulfates?

A

Add dilute hydrochloric acid then barium chloride solution-a white precipitate tells you sulfate ions are present

29
Q

How do you test for halides?

A

Add dilute nitric acid then silver nitrate solution

30
Q

What Colour precipitates do chloride, bromide and iodide ions form?

A
  • White
  • Cream
  • Yellow
31
Q

What are benefits of modern instrumental methods?

A
  • Highly accurate and sensitive
  • Quicker
  • Enable very small samples to be analysed
32
Q

What are the disadvantages of using instrumental methods?

A
  • Expensive
  • Requires specialist training
  • Gives results that can only be interpreted by comparison with data from known substances
33
Q

How does flame emission spectroscopy work?

A
  • Sample is heated in a flame
  • This energy causes electrons to jump into higher shells
  • When the electrons fall back down, the energy is released as light energy
  • In a spectrosope, the wavelengths are analysed to produce a line spectrum
  • This is compared to data base values

Chemistry (12 decks)

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