8. Chemical analysis Flashcards

1
Q

In chemistry what is a “pure” substance?

A

A substance made of a single element or compound

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2
Q

How can pure substances be distinguished from impure ones?

A

By their melting/boiling points

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3
Q

Describe the melting and boiling points of pure substances

A

One very specific temperature

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4
Q

Describe the melting and boiling points of impure substances

A

They change state at a range of temperatures

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5
Q

What is a formulation?

A

A complex mixture designed as a useful product

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6
Q

Give three examples of formulations

A

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

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7
Q

In paper chromatography, what is the stationary phase and what is the mobile phase

A

Paper is stationary, solvent (usually water or ethanol) is mobile

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8
Q

How can chromatography show the difference between pure and impure substances?

A

Pure ones will not separate into a number of spots

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9
Q

How is the Rf value calculated?

A

distance moved by spot/distance moved by solvent

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10
Q

In chromatography, why must the substances be placed on a pencil line?

A

Pencil will not dissolve in the solvent

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11
Q

In chromatography why must the solvent height be lower than the pencil line?

A

So that the substances do not dissolve into the solvent off the paper

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12
Q

How can hydrogen be tested for?

A

Makes a squeaky pop when a splint is placed in it

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13
Q

How can oxygen be tested for?

A

Relights a glowing splint

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14
Q

How can carbon dioxide be tested for?

A

Bubble through limewater, turns it milky (cloudy)

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15
Q

How can chlorine be tested for?

A

Bleaches damp litmus paper white

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16
Q

What is the colour of the flame produced from a lithium containing compound?

A

Crimson

17
Q

What is the colour of the flame produced from a copper containing compound?

A

Green

18
Q

What is the colour of the flame produced from a sodium containing compound?

A

Yellow

19
Q

What is the colour of the flame produced from a potassium containing compound?

A

lilac

20
Q

What is the colour of the flame produced from a calcium containing compound?

A

Orange-red

21
Q

Which solutions produce white precipitates on addition of sodium hydroxide?

A

Solutions containing aluminium, magnesium, calcium ions

22
Q

What is the test for carbonates?

A

Add an acid to generate carbon dioxide gas

23
Q

What is the test for halides?

A

Add silver nitrate and nitric acid to generate a solid silver halide precipitate

24
Q

What is the test for sulfate ions?

A

Add barium chloride and hydrochloric acid, forms white precipitate

25
Q

How is flame emissions spectroscopy carried out?

A

Sample placed in a flame, light emitted is passed through a spectroscope to give a spectrum which can be compared to a reference