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chemistry > chemical analysis - C8 > Flashcards

chemical analysis - C8 Flashcards

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1
Q

what is a pure substance

A

a substance that contains only one type of element or compound

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2
Q

what is the difference of the boiling points of pure and impure substances

A

pure substances boil at specific temperatures
impure substances boil over a range of temperatures

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3
Q

us checking for boiling point a physical or chemical test

A

physical

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4
Q

what is formulation?

A

-they are mixtures that have a specific formula
-a mixture made suing precise amounts of different components, each having a specific purpose

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5
Q

give examples of formulations

A

paint, medicines , cleaning agents, fertilisers, alloys, some food and drinks

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6
Q

what is chemical analysis

A

the instruments and methods we use to identify, separate and quantify different substances.

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7
Q

what are the precautions to take when testing for chlorine gas

A

-wear a gas mask
- do it in a fume cupboard

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8
Q

how do we test for carbonate ions?

A

when a carbonate reacts with an acid it forms a salt, carbon dioxide and water
-so add dilute HCL
-collect any gas and bubble it through lime water
-if it turns cloudy then carbonates were present

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9
Q

how do we test for sulfate ions

A

-add dilute HCL to get rid of any carbonates
-add barium chloride
-if a white precipitate forms, barium sulfate has formed which means sulfate ions are present

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10
Q

how do we test for halides

A

-add dilute nitric acids to get rid of any impurities
-then add silver nitrate
-if it forms a white precipitate = chloride ions
-cream precipitate = bromide ions
-yellow precipitate = iodide ions

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11
Q

how can we test for cations

A

flame tests and sodium hydroxide tests

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12
Q

how do you carry out a flame test

A

-dip a nichrome wire in some HCL, then rinse it off with water and put it over a bunsen burner flame to clean it
-the dip the nichrome wire loop in the compound you want to test
-put it in the blue part of the flame

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13
Q

what flame do sodium ions give

A

yellow

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14
Q

what flame do potassium ions give?

A

lilac

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15
Q

what flame do lithium ions give

A

crimson

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16
Q

what flame do copper ions give

A

green

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17
Q

what flame do calcium ions give

A

orange-red

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18
Q

how do the sodium hydroxide test work

A

when a metal ion reacts with sodium hydroxide it forms a precipitate which makes the solution a certain colour

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19
Q

what precipitate do copper ions give

A

blue precipitate

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19
Q

what precipitate do calcium ions give

A

white

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19
Q

what precipitate do iron 2 ions give

A

green

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19
Q

what precipitate do iron 3 ions give

A

brown

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19
Q

what precipitate do magnesium ions give

A

white

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19
Q

what precipitate do aluminium ions give

A

white but if excess sodium hydroxide is added it turns colourless

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20
Q

how does flame emission spectroscopy work

A

-metal ion is heated until it emits light
-the light is detected by a spectroscope which can detect the different wavelengths of light
-each cation produces a unique combination of wavelengths and will put these onto a unique spectrum
-then we can identify the cation

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20
Q

what does the intensity of the lines mean

A

the concentration of the metal ions

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20
Q

what happens if there is more than one ion

A

the different wavelengths are put onto a single spectrum

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21
Q

what is flame emission spectroscopy an example of

A

an instrumental method

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22
Q

what are the benefits of using instrumental methods

A

more accurate, more sensitive, more quick

23
Q

what are ceramics

A

brittle hard materials that are heat resistant and corrosion resistant

24
Q

what are the two types of ceramics

A

clay ceramics and glass

25
Q

how are clay ceramics formed

A

-shaping clay then heating it until it becomes hard
-they have high compressive strength so can be used in bricks
-also includes china and porcerlain

26
Q

how is glass formed

A

soda-lime glass
-melting sand, sodium carbonate and limestone
-moulding it then allowing it to solidify
borosilicate glass
- with melting boron trioxide and sand
-a lot higher melting point than soda lime
-is strong, hard and good thermal insulator so can be uses in windows

27
Q

what are composites

A

substances with two or more materials with different properties that are combines to get a product with desirable properties

28
Q

what are composites made of

A

reinforcement - long solid fibres/fragments
matrix- what holds fibres together , usually soft then goes hard

29
Q

what are polymers

A

large molecules with high relative mass made by joining smaller monomers together

30
Q

what is low density polyethene

A

made in- moderate temperatures, high pressures, catalyst
-flexible but weak
-used in carrier bags

31
Q

what is high density polyethene

A

made with- low temperatures and pressures with catalyst
-rigid but strong
-used in drainage pipes

32
Q

what properties to polymers usually have

A

flexible, easily shaped, good conductors of heat and electricity

33
Q

what are thermosoftening polymers

A

layers of polymers held together by weak intermolecular forces
-when heated it melts the forces break so they can be changed shape

34
Q

what are thermosetting polymers

A

layers of polymers held by strong intermolecular forces so when heated they don’t break so they are hard strong and rigid

35
Q

what is corrosion

A

when metals slowly break down due to reacting with substances in their environment

36
Q

how does iron rust

A

by being exposed to water and oxygen

37
Q

in a rusting reaction, what is oxidised and what is reduced

A

iron oxidised
oxygen reduced

38
Q

if there are 3 test tube
-with water and a layer of oil
-with air and just calcium chloride
-with just water
which one will the nail rust in?

A

the one with just water
the layer of oil blocks oxygen from dissolving in the water
the calcium chloride removes all water vapour from the air

39
Q

how can we avoid rust

A

barrier methods and sacrificial methods

40
Q

what is a barrier method

A

blocking oxygen and water from coming in contact with metal
-coating with paint
-oiling and greasing
-electroplating

40
Q

what is a sacrificial method

A

adding a more reactive metal to the iron so that the oxygen reacts with that metal

41
Q

give an example of a method that is both barrier and sacrificial

A

coating in zinc

42
Q

why doesn’t aluminium rust the same way iron does

A

because when the aluminium rust with the air it forms a protective layer so the air can’t reach the rest of the metal

43
Q

what is sustainable development

A

an approach to human and economic growth to make substances that meet the needs of current generations and won’t compromise the chance to meet the needs of future generations

44
Q

what is reusing

A

using a material again either for the same or different purposes

45
Q

what is recycling

A

collecting and processing materials that would have been thrown away and turning them into new products

46
Q

what is the benefit of using recycled aluminium

A

-wont have to dig to get its ore
wont have to use electrolysis to separate it them

47
Q

what are the purpose of life cycle assessments

A

to see the effect a product has on the evironment

48
Q

what are the steps to looking at a life cycle assesment

A

extracting and processing raw materials
-manufacturing and processing them
-using them
-disposing of them

49
Q

what are things that aren’t good for the environment

A

pollutants, energy usage, landfills, mines, cutting down trees

50
Q

What are the 3 things needed for water to be potable

A

Low amount of dissolved substances
-no microorganisms
-pH between 6.5 and 8.5

51
Q

Where do we get potable water from

A

Fresh water = water exposed to air = rivers, lakes and resouvairs
Ground water = aquifers

52
Q

How do we make water potable

A
  1. Pass though wire mesh to remove big things
    2.pass through sand and gravel mixture to remove small things
    3.steralise it
53
Q

How can we steralise water

A

Pumping chlorine gas through it . Exposing it to ozone of ultraviolet radiation

54
Q

How do countries with low rainfall get potable Water

A

Desalination

55
Q

What are the two ways to do desalination

A

Simple distillation and reverse osmosis

56
Q

What are the ways waste water is created

A

Domestic, agricultural and industry

57
Q

How is waste water treated

A
  1. Screening - passed though mesh to filter large items
  2. Sedimentation - sits in tank so heavier atoms go to the bottom as sludge, the top is effluent .
    3.effluent is aerobically digested by microorganisms
    4.sludge is anaerobically digested to produce methane
    Sludge left over can be used as fertiliser
58
Q

Why is the Haber process important

A

The ammonia is urself for fertilisers

59
Q

How does the haber process work

A

Nitrogen and ammonia are fed though to the left side of the chamber with and iron catalyst. here is is 450 degrees and pressure is 200 . Some will join together to form ammonia others won’t . So the gas is fed through to a cooler part and ammonia condenses first as it has a higher boiling point that nitrogen and ammonia

60
Q

Why do plants need npk fertilisers

A

To absorb the nutrients

61
Q

Describe the nitrogen part of npk

A

Nitrogen is needed to make amino acids for proteins for growth
Nitrogen comes from ammonia
Ammonia can react with nitric acid to make ammonium salts. Can react with oxygen and water to make nitric acid

62
Q

Describe the phosphorus part of npk

A

Phosphate can be
mined as cphosphate rock but
the salts in it are insoluble so plants can’t use them so the phosphate rocks react with acid to make soluble salts
Nitric acid - make phosphoric acid and calcium nitrate
Sulphuric acid - makes calcium sulphate and calcium nitrate = single superphosphate
Phosphoric acid - makes calcium phosphate = triple superphosphate

63
Q
A

chemistry (10 decks)

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