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1[GCSE Chemistry]1 > Topic 9 - Separate Chemistry 2 > Flashcards

Topic 9 - Separate Chemistry 2 Flashcards

1
Q

Why must the test for any ion be unique?

A

There are several different tests to detect and identify the ions in compounds. It is important that the test for any ion is unique. The results of a test must let you determine which ion is present, rather than being uncertain about which ion it is.

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2
Q

How do you test for cation?

A

flame test or sodium hydroxide test

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4
Q

How do you conduct a flame test?

A
  1. dip a clean wire loop into a solid sample of the compound being tested 2. put the loop into the edge of the blue flame from a Bunsen burner 3. observe and record the flame colour produced
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5
Q

How do you test for metal cation using sodium hydroxide?

A
  1. You add a few drops of sodium hydroxide solution to a solution of your mystery compound 2. If a hydroxide precipitate forms, you can use its colour to tell which metal ion was in the compound.
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6
Q

What colour is the precipitate when these metal ions are present? A - Aluminium B - Calcium C - Copper D - Iron (II) E - Iron (III)

A

A - Al^3+ - White at first then colourless B - Ca^2+ - White C - Cu^2+ - Blue D - Fe^2+ - Green E - Fe^3+ - Brown

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7
Q

How do you work out whether a substance contains ammonium ions?

A
  1. Add some sodium hydroxide solution to a solution of the mystery compound. 2. Now heat it gently 3. If ammonia gas is given off then, it means there are ammonium ions in the mystery substance 4. Test for ammonia gas by holding a piece of damp red litmus paper. 5. If the red litmus paper turns blue, ammonia gas is present
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8
Q

What colour would you get for testing these ions with a flame? A - Lithium B - Sodium C - Potassium D - Calcium E - Copper

A

A - Li+ - red B - Na+ - yellow C - K+ - lilac D - Ca^2+ - orange-red E - Cu^2+ - blue-green

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9
Q

How do you test for halide ions?

A
  1. add a few drops of dilute nitric acid to the sample 2. add a few drops of dilute silver nitrate solution 3. Observe and record the colour of any precipitate that forms. Chloride - Cl- - White Bromide - Br- - Cream Iodide - I- - Yellow
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10
Q

How do you test for carbonate ions?

A

Carbonate ions, CO32- are detected using a dilute acid. Bubbles are given off when an acid, usually dilute hydrochloric acid, is added to the test compound. The bubbles are caused by carbon dioxide. Limewater is used to confirm that the gas is carbon dioxide. It turns milky when carbon dioxide is bubbled through it. The test for carbonate ions works whatever acid is added.

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11
Q

How do you test for sulfate ions?

A

Barium ions react with sulfate ions, SO42- to form insoluble white barium sulfate: Ba2+(aq) + SO42-(aq) → BaSO4(s) To test for sulfate ions in solution: 1. add a few drops of dilute hydrochloric to the sample 2. add a few drops of dilute barium chloride solution 3. A white precipitate forms if sulfate ions are present.

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12
Q

What is flame photometry?

A

It is an instrumental method that allows you to identify ions in a dilute solution. In the flame photometer, the coloured light from a vaporised sample can be split to produce an emission spectrum. The different lines in an emission spectrum look like a coloured barcode. Each metal ion produces a unique emission spectrum. The metal present in a sample is identified by comparing its spectrum with reference spectra. These are emission spectra from known metal ions. If two spectra match, they must be from the same metal ion.

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13
Q

What is the advantages of using instrumental analysis (tests that use machines)?

A
  • Very sensitive - they can detect even the tiniest amounts of substances - Very fast and tests can be automated - Very accurate - don’t involve human error
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14
Q

How do you identify the ions in unknown salts, using the tests for the specified positive and negative ions?

A
  1. Carry out one or more tests (Flame test, Hydroxide precipitate test, Ammonium test, Halide ion test, Sulfate ion test and Carbonate ion test) on each salt. You may need to dissolve a sample of salt in a little distilled water if you are given solids, rather than solutions. 2. Record your observations carefully. Repeat any tests that do not get clear results.
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15
Q

What is the formula of the first first four alkanes?

A

Methane - CH4 Ethane - C2H6 Propane - C3H8 Butane - C4H10

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16
Q

Draw the structure of the first four alkanes

A
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17
Q

Why are the alkanes saturated hydrocarbons?

A

All the atoms have formed bonds with as many other atoms as they can.

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18
Q

What are the formulas of 3 alkenes?

A

Ethene - C2H4 Propene - C3H6 Butene - C4H8

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19
Q

Draw out the structures of the three alkenes (Butene1 and Butene2)

A
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20
Q

Why are alkenes unsaturated?

A

This is because they can make more bonds - the double bond can open up, allowing the two carbon atoms to bond with other atoms

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21
Q

What happens in the reaction of bromine with ethene?

A

The two Br atoms join with the ethene so each carbon atom is joined to 1 bromine atom and 2 hydrogen atom.

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22
Q

How is bromine water used to distinguish between alkenes and alkanes?

A

An orange-brown solution of bromine dissolved in water, called bromine water, is used to distinguish between alkanes and alkenes: - there is no change when bromine water is mixed with an alkane - the bromine water becomes colourless when it is mixed with an alkene

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23
Q

Describe complete combustion for alkanes and alkenes.

A

The complete combustion of alkanes and alkenes involves the oxidation of hydrocarbons. Carbon dioxide and water are produced. For example: Ethane + oxygen → carbon dioxide + water C2H6(g) + 3½O2(g) → 2CO2(g) + 3H2O(l) Ethene + oxygen → carbon dioxide + water C2H4(g) + 3O2(g) → 2CO2(g) + 2H2O(l) Notice that more molecules of oxygen are needed to balance the equation for ethane, because the alkane contains more hydrogen atoms which need to be oxidised to form water molecules

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24
Q

What is a polymer?

A

Substance of high average relative molecular mass made by joining up lots of small repeating units called monomers.

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25
Q

What is addition polymerisation?

A

Lots of unsaturated monomer molecules can open up and join together to form polymer chains. Ethene (C2H4) becomes poly(ethene) - (C2H4)small n Draw in structure form

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26
Q

How do get from the displayed formula of the polymer to the displayed formula of the monomer?

A

Draw out the repeating bit of the polymer, get rid of the two bonds going out through the brackets and put a double bond between the carbons. Don forget the n or the number of repeating units on the bottom right.

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27
Q

How are the properties of poly(ethene) related to its use?

A

Flexible, electrical insulator and cheap - Plastic bags, bottles and wire insulation

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28
Q

How are the properties of poly(propene) related to its use?

A

Flexible, strong, tough, moldable - crates, furniture, ropes

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29
Q

How are the properties of poly(chloroethene) or PVC related to its use?

A

Tough, cheap - water pipes, window frames

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30
Q

How are the properties of poly(tetrafluorethene) or PTFE related to its use?

A

Unreactive, tough, non-stick - non-stick pans, waterproof clothing

31
Q

What is the problem with the availability of starting materials?

A

Plastics are a type of polymer which are made from crude oils and crude oils are a finite resource and will eventually run out.

32
Q

What are the problems with polymers being disposed via landfill sites?

A
  • A lot of plastics get dumped in landfill sites. This is usually when different polymers are too difficult or expensive to separate and recycle. - Lots of valuable land is quickly getting used up for use as landfill sites. - Most polymers are non-biodegradable - they’re not broken down by microorganisms. This means that they will sit in landfill forever.
33
Q

What are the problems associated with disposing polymers via combustion?

A
  • Burning plastics produces a lot of energy and this can be used to generate electricity. But it’s not all rainbows and smiles.. - If not carefully controlled, toxic gases can be released from the combustion of plastics. For example, when polymers that contain chlorine (such as PVC) are burned, they produce HCI this has to be removed. - Carbon dioxide is also produced and this contributes to global warming.
34
Q

What are the advantages of recycling polymers?

A
  • Reduces the amount of non-biodegradable waste filling up landfill sites. - Reduces emissions of greenhouse and toxic gases eneray resources than when making new plastics.. which can be released from burning polymers. - Recycling generally uses up less water - Reduces the amount of crude oil needed to produce more plastics. - Recycling generally saves money and creates jobs
35
Q

What are the disadvantages of recycling polymers?

A
  • Polymers must be separated by type before they can be melted and reformed into a new product this can be diffiult and expensive - Polymers can only be recycled a finite number of times. . - If polymers are mixed together, the quality of the final recycled polymer product could be reduced. - Over time, the strength of the polymer can decrease. -Melting down polymers can release dangerous gases into the atmosphere. These are harmful to plants and animals.
36
Q

What are some naturally occurring polymers?

A
  • DNA - polymer made form four different monomers called nucleotides - Amino acid monomers form polymers known as proteins via condensation polymerisation - Starch and cellulose are large, complex carbohydrates, which are made up of many smaller units of carbohydrates known as sugars, joined together
37
Q

What are the formulae of methanol, ethanol, propanol and butanol?

A

Methanol - CH3OH Ethanol - C2H5OH Propanol - C3H7OH Butanol - C4H9OH

38
Q

What is the general formula of the alcohols and what is the functional group?

A

All alcohols contain an -OH functional group. The general formula is C(n)H(2n+1)OH.

39
Q

How can alkenes be produced from alcohols?

A

Alcohols can be dehydrated to from alkenes.

40
Q

What are Carboxylic acids? (4)

A

They are another homologous series of molecules. They have a general formula of C(n-1)H(2n-1)COOH and they have a functional group of - COOH. They have typical acidic properties.

41
Q

What are the formulae of the first four carboxylic acids?

A

Methanoic acid - HCOOH Ethanoic acid - CH3COOH Propanoic acid - C2H5COOH Butanoic acid - C3H7COOH

42
Q

How can carboxylic acids be formed from their alcohols?

A

They can each be formed by oxidising the alcohol which contains the same total number of carbons.

43
Q

What do members of the same homologous series have in similar?

A

They have similar reactions because they contain the same functional reactions. So if you know how a certain molecule in a homologous series reacts, you can predict how other molecules in that series react.

44
Q

What is fermentation?

A

The process of using yeast to convert a type of carbohydrate called sugars into alcohol.

45
Q

What is the symbol equation of fermentation?

A

C6H1206 —(YEAST)—> 2C2H5OH + 2CO2

46
Q

Where is glucose taken from for fermentation?

A

Sugar canes or sugar beet plants

47
Q

What are the 4 condition of fermentation?

A
  1. 30-40˚c 2. Catalyst - yeast 3. Anaerobic (No oxygen) 4. Glucose must be dissolved?
48
Q

Why should fermentation happen between 30-40˚c?

A

Fermentation happens best at this temperature

49
Q

Why is yeast needed in fermentation?

A

To speed up the reaction

50
Q

Why should fermentation be anaerobic?

A

This is so that the oxygen doesn’t convert ethanol into ethanoic acid - this would be distasteful.

51
Q

Why must the glucose be dissolved in fermentation?

A

This is so that the glucose can react with the yeast.

52
Q

Why does fermentation stop before the alcohol is 100% concentrated?

A

Fermentation stops when the concentration of the alcohol reaches 20% because this is when the yeast is killed off. The yeast will fall to the bottome

53
Q

How can the mixture produced from fermentation become more concentrated?

A

It can be distilled to produce a more concentrated alcohol.

54
Q

How can fractional distillation and filtration help to achieve a higher concentration of ethanol?

A

The fermentation mixture contains yeast cells and insoluble substances. These are separated from the impure ethanol solution by filtration. Fractional distillation is then used to produce a concentrated solution of ethanol from the filtrate. This works because ethanol and water have different boiling points. When the mixture is heated, ethanol evaporates more easily.

55
Q

Describe a nanoparticle

A

Nanoparticles are structures, 1-100 nanometres (nm) in size, that usually contain only a few hundred atoms. This means that nanoparticles are around 100 times larger than atoms and simple molecules

56
Q

Describe a nanoparticulate

A

A substance that consists of nanoparticles is described as being nanoparticulate. A nanoparticulate substance has different properties from the same substance in bulk (powders, lumps and sheets). This is because of the small size and large surface area to volume ratios of nanoparticles.

57
Q

Describe how the properties of nanoparticulate materials relate to their uses

A

Nanoparticulate materials are used in some paints, cosmetics and sunscreens. Sunscreens block harmful ultraviolet light from the sun reaching the skin. Titanium dioxide blocks ultraviolet light, so it is used in sunscreens. In bulk titanium dioxide is white – it is used as a pigment in white paint. However, nanoparticulate titanium dioxide has no colour and cannot be seen when it is spread on the skin. Many people prefer nanoparticulate sunscreen because it is not obvious that they are wearing it.

58
Q

What are some risks associated with nanoparticulate materials? (4)

A

Some people are concerned that the small size of nanoparticles makes it possible to breathe them in, or for them to pass into cells. Once inside the body, they might catalyse reactions that are harmful. Toxic substances could bind to them because of their large surface area to volume ratios, harming health if the nanoparticles do get into the body. Modern nanoparticulate materials have only become common recently, so it is difficult for scientists to determine their risks.

59
Q

Glass Clay Metals Appearance: ______ / ______ / ______ Melting point: ______ / ______ / ______ Malleable/brittle: ______ / ______ / ______ Ability to conduct electricity: ______ / ______ / ______ Ability to conduct heat: ______ / ______ / ______

A

Glass Clay Metals Appearance: Transparent / Opaque / Shiny Melting point: High / High / High Malleable/brittle: Brittle / Brittle / Malleable Ability to conduct electricity: Poor / Poor / Good Ability to conduct heat: Poor / Poor / Good

60
Q

Describe glass ceramics

A

Glass is made by melting sand with other substances (especially metal oxides), then allowing the molten liquid to cool and solidify. Glass is transparent and hard, but it is brittle. This makes it useful as windows as it is transparent.

61
Q

Describe clay ceramics

A

Clay ceramics include brick, china and porcelain. They are made by heating clay to high temperatures, which causes crystals to form and join together. Clay ceramics are often coated with a glaze, which hardens on heating to form a hard, smooth, opaque and waterproof layer.

62
Q

Describe metals

A

Metals are malleable and ductile, so they can be bent into shape or made into wires without shattering. Unlike glass and clay ceramics, metals are good electrical conductors.

63
Q

Describe polymers

A

Polymers are poor conductors of electricity and heat, but their other properties vary depending upon the particular polymer. For example, they can be transparent or opaque. They are often tough and flexible, but some are hard and brittle.

64
Q

What are composite materials?

A

A composite material consists of two or more materials with different properties. They are combined to produce a material with improved properties. Most composite materials have two components: - the reinforcement - the matrix, which binds the reinforcement

65
Q

Give examples of composite materials. (4)

A
  • Reinforced concrete : Steel (Reinforcement) + Concrete (Matrix) - Fibreglass: Glass fibres (Reinforcement) + Polymer resin (Matrix) - Carbon fibre reinforced polymer: Carbon fibres (Reinforcement) + Polymer resin (Matrix) - Chipboard: Wood chips (Reinforcement) + Resin glue (Matrix)
66
Q

How do you determine which material has which use?

A

The properties of a material determine whether it is suitable for a given use. For any given use, certain properties will be required. There may be more than one suitable material to choose from, and the advantages and disadvantages of each one must be evaluated.

67
Q

Describe condensation polymerisation (5)

A

Usually involves two different types of monomers. The monomers react together and bonds form between them making polymer chains. Each monomer has at least two functional groups, one on each end of the the molecule. Each functional group can react with the functional group of another monomer, creating long chains of alternating monomers. For each new bond that forms, a small molecule is lost (e.g. water).

68
Q

When do polyesters form?

A

When dicarboxylic acid monomers and diol monomers react together.

69
Q

What are dicarboxylic acid monomers and diol monomers?

A

Dicarboxylic acid monomers are carboxylic acids with two -COOH (carboxylic acid) groups. Diol monomers are alcohols with two -OH (alcohol) groups.

70
Q

When does an ester link form?

A

When the carboxylic acid group reacts with the alcohol group in condensation polymerisation.

71
Q

Why are polyesters a condensation polymer?

A

Each time an ester link is formed, a small molecule (water) is lost.

72
Q

Investigate the temperature rise of produced in a known mass of water by the combustion of alcohols: Ethanol, Propanol, Butanol and Pentanol. (8)

A

1) Put a alcohol into a spirit burner and measure the mass of the burner (with cap) and fuel using a mass balance. 2) Fill a metal can with 100cm3 of water and put it on a tripod and put a lid on it. 3) Take the initial temperature of the water and put the spirit burner under it, remove the cap and light it. 4) Make sure the apparatus is surrounded with a draught screen to reduce air flow 5) After the water has risen in temp by 40˚c then replace the cap and reweigh the burner and fuel. 6) Record the change in mass and change in temp 7) Repeat for all other alcohols 8) Finally, calculate the mass of each alcohol burned to produce 1˚c rise in temp

1[GCSE Chemistry]1 (35 decks)

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