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Chemistry 2 > Chromatography and gas tests > Flashcards

Chromatography and gas tests Flashcards

1
Q

What is a pure substance

A

It is a single element or compound which isn’t mixed with any other substance,

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2
Q

State properties of pure substances

A

Pure substances melt and boil at specific temperatures, heating graphs can be used to distinguish pure substances from impure.
Melting point of a pure substance has straight lines on graph
Melting point of an impure substance has curvy lines on graph

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3
Q

What is a formulation

A

It is a mixture that has been designed as a useful product

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4
Q

How are formulations made

A

By mixing chemicals that have a particular purpose in carefully designed quantities.

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5
Q

State examples of formulations

A

Fuels, cleaning agents, paints, medicines and fertilisers.

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6
Q

What is chromatography?

A

It can be used to separate mixtures and help identify substances

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7
Q

What does chromatography involve?

A

A mobile phrase (e.g water or éthanol) and a stationary phase (e.g chromatography paper)

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8
Q

What are Rf values

A

The ratio of the distance moved by a compound to the distance moved by the solvent

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9
Q

How are Rf values calculated?

A

Distance moved by substance / distance moved by solvent (mobile phase, water)

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10
Q

How are pure substances distinguished in comparison to impure substances on chromatography paper?

A

Pure substances will produce a single spot in all solvents whereas an impure substance produces multiple spots.

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11
Q

State 5 ways to separate mixtures

A

Chromatography
Filtration
Crystallisation (evaporation)
Distillation
Fractional distillation

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12
Q

In paint, what is known by the terms ‘binder’ ‘solvent’ and ‘pigment’

A

Binder - helps the paint attach itself to an object
Solvent - helps the binder and pigment spread by thinning them out
Pigment - to provide colour.

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13
Q

In cleaning fragrances, what is meant by the terms ‘water’ ‘surfactant’ ‘colouring / fragrance’ and ‘rinse agent’ ?

A

Water - thins out the mixture so it can be sprayed easier from the bottle
Surfactant - the actual detergent that helps the remove stains or grease
Colouring / fragrance - improves appeal to customers
Rinse agent- helps water drain off crockery.

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14
Q

What can chromatography help detect?

A

Drugs, explosives, dyes and paints

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15
Q

The resulting pattern of colour in chromatography is called…

A

A chromatogram

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16
Q

State the 7 steps to chromatography

A

1- draw a pencil line on a piece of chromatography paper
2- pour some water into beaker
3-stand paper in beaker (water must be below pencil line)
4-spot the mixture needed to be separated
5- let the spot dry
6- leave until water has almost reached top of paper
7- remove the paper and hang chromatogram up to dry

17
Q

What do we refer an unknown as in chromatography?

A

U

18
Q

What is a stationary and mobile phase?

A

Stationary - isn’t moving
Mobile- moving

19
Q

What is an unknown substance?

A

A substance nor shared between multiple in common substances.

20
Q

How can a substance be identified on a database?

A

The Rf of an unknown substance is compared with values of other substances on an online database.

21
Q

What is a solvent front?

A

The point where the solvent stops moving

22
Q

What does soluble mean?

A

Ability to be dissolved

23
Q

What does solution mean?

A

A homogenous mixture of two or more substances

24
Q

What is a solute?

A

A solid, liquid or gas which is dissolved to make a solution

25
Q

What is a solvent

A

Any substance, tropically a liquid, which is capable of dissolving one or several substances, thus creating a solution.

26
Q

What is the test for chlorine gas?

A

Litmus paper is used, and if chlorine is present the damp blue litmus paper turns red, and then bleached it white.
Chlorine also makes damp starch- iodide paper turn blue / black
Toxic

27
Q

What is the test for oxygen

A

Small amount of manganese oxide is placed in 15cm ³ of hydrogen peroxide, a blown out splint will relight in the conical flask.

28
Q

What is the test for carbon dioxide?

A

When carbon dioxide is shaken or bubbled through limewater, the limewater turns cloudy (/milky) a solid calcium carbonate has been formed

29
Q

What is the test for hydrogen?

A

A burning splint held near a flask of pure hydrogen gas ignited with a squeaky ‘pop’ sound

30
Q
A

Chemistry 2 (7 decks)

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