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Chemistry > C9: Seperate Chemistry 2 > Flashcards

C9: Seperate Chemistry 2 Flashcards

1
Q

What is an ion?

A

A charged atom, molecule or particle.

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2
Q

Why must a test for a specific ion be unique?

A

Tests are used to identify ions and must be unique so that the test gives an easily observed result which is specific to the ion that is present.

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3
Q

Describe how you would carry out a flame test to test for ions?

A
  • Clean a nichrome wire using hydrochloric acid.
  • Turn the Bunsen burner onto the blue flame.
  • Dip the wire in a solution of the substance being tested.
  • Place the wire in the flame and record the colour.
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4
Q

What is the result of the flame test on lithium ions?

A

Red flame

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5
Q

What is the result of the flame test on sodium ions?

A

Yellow flame

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6
Q

What is the result of the flame test on potassium ions?

A

Lilac flame

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7
Q

What is the result of the flame test on calcium ions?

A

Orange-red flame

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8
Q

What is the result of the flame test on copper ions?

A

Blue-green flame

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9
Q

Why must the wire be cleaned before carrying out a flame test?

A

To remove any unwanted ions that might obscure the colour of the flame.

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10
Q

Why can a flame test not be used when a compound contains a mixture of metal ions?

A

The flame colours of the ions will blend together so the individual flame colours won’t be seen meaning the ions can’t be identified.

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11
Q

What is a precipitate?

A

An insoluble solid suspended in a liquid.

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12
Q

Without using the flame test, how can you test for aqueous metal ions?

A

Add sodium hydroxide solution to the metal ions. Observe the colour of the precipitate.

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13
Q

What colour precipitate forms when sodium hydroxide reacts with aluminium ions?

A

White

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14
Q

What colour precipitate forms when sodium hydroxide reacts with copper(Il) ions?

A

Light Blue

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15
Q

What colour precipitate forms when sodium hydroxide reacts with iron(Il) ions?

A

Green

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16
Q

What colour precipitate forms when sodium hydroxide reacts with iron(Ill) ions?

A

Red-Brown

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17
Q

What has to be added as well as sodium hydroxide to find the precipitate for ammonium ions?

A

Damp red litmus paper

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18
Q

What colour precipitate forms when sodium hydroxide and damp red litmus paper reacts with ammonium ions?

A

damp red litmus paper turns blue (ammonia gas produced)

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19
Q

How can you test for carbonate ions?

A

add acid and bubble gas through limewater

If carbonate ions are present CO2 is produced which will turn the limewater cloudy

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20
Q

How can you test for sulfate ions?

A

add barium chloride

If Sulfate ions are present then a white precipitate forms

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21
Q

How can you test for Iodide ions?

A

Add nitric acid and silver nitrate

If Iodide ions are present then a yellow precipitate forms

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22
Q

How can you test for Bromide ions?

A

Add silver nitrate and nitric acid

If bromide ions are present then a cream precipitate forms

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23
Q

How can you test for Chloride ions?

A

Add silver nitrate and nitric acid

If Chloride ions are present then a white precipitate forms

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24
Q

What is meant by the phrase instrumental methods of analysis?

A

Methods of analysis that use machinery such as mass spectrometry and gas chromatography.

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25
What are the benefits of using instrumental methods for analysis?
- Accurate - Sensitive - Quick to carry out
26
What is a flame photometer?
A device used in inorganic analysis. It can be used to identify or determine the concentration of metal ions.
27
How can a flame photometry be used to identify metal ions?
An emission spectrum is produced by the flame photometer. Each metal ion produces a unique spectrum so comparing the unknown spectrum to reference spectra can identify the ion.
28
How can a flame photometry be used to determine the concentration of metal ions?
Take readings using a flame photometer of the metal ions at different concentrations. Plot a calibration curve. Take a reading of the unknown sample and compare to the curve.
29
What is the major advantage of flame photometry compared to simple flame testing?
Flame photometry can be used to analyse a mixture of ions whereas flame tests can only be used to identify one ion at a time.
30
What is the general formula for alkanes?
CnH2n+2
31
Name the first four alkanes and write their molecular formulae
Methane - CH4 Ethane - C2H6 Propane - С3Н8 Butane - C4H10
32
What is the rhyme to remember the number of carbons each alkane has?
Monkeys (Methane) 1 Eat (Ethane) 2 Peanut (Propane) 3 Butter (Butane) 4
33
What type of bond are formed between carbon and hydrogen atoms in alkanes?
Covalent bonds
34
Why are alkanes saturated hydrocarbons?
Saturated - all C-C bonds are single bonds. Hydrocarbon - only contain carbon and hydrogen atoms.
35
What is the general formula for alkenes?
CnH2n
36
Name the first four alkenes and write their molecular formulae?
Ethene - C2H4 Propene - C3H6 Butene - C4H8 Pentene - C5H10
37
Why are alkenes unsaturated hydrocarbons?
They are compounds made up of only carbon and hydrogen atoms and they contain double carbon bonds, C=C.
38
Why can methane not be an alkene?
Because it only has one carbon so it can’t have a carbon double bond
39
What is a functional group?
The group of atoms responsible for the main chemical properties of a compound.
40
What functional group do alkenes contain?
C=C double bond.
41
What is the difference between but-1-ene and but-2-ene?
But-1-ene and but-2-ene are both alkenes with 4 carbons but the C=C bond is found between different carbons in the chain. In but-1-ene, the double bond is between the first and second carbon whereas in but-2-ene, it is between the second and third carbon in the chain.
42
How can bromine water be used to distinguish between alkanes and alkenes?
When bromine water is added to an alkane, the solution remains brown. When bromine water is added to an alkene, the solution changes from brown to colourless.
43
Why do alkenes decolourise bromine water?
Alkenes are unsaturated. The double bond allows alkenes to react with bromine to form a bromoalkane.
44
What is produced when a hydrocarbon is completely combusted? Describe what happens to the carbon and hydrogen?
Water and carbon dioxide are produced. Carbon and hydrogen are oxidised.
45
Energy is released when hydrocarbons undergo complete combustion. What type of reaction is occurring?
An exothermic reaction.
46
What is a polymer?
A substance of high average relative molecular mass made up of small repeating units.
47
How are polymers made?
By linking together lots of small molecules (monomers) to form a long chain.
48
What is the name of the process in which ethene molecules join together to form a polymer?
Addition polymerisation.
49
How can ethene molecules undergo polymerisation to form the polymer poly(ethene)?
One of bonds in each C=C double bond breaks and forms a bond with an adjacent monomer, forming a long chain polymer. This requires many ethene monomers.
50
What is the name of the product formed from the addition polymerisation of ethene?
Poly(ethene)
51
Can chloroethene undergo addition polymerisation? If so, what is the product?
Yes because it contains a C=C double bond. The product is poly(chloroethene) or PVC.
52
What properties of poly(propene) makes it suitable for making buckets and crates?
- Flexible - Strong
53
Poly(ethene) is commonly used to make plastic bags, bottles and coating of electrical wires. Why?
- Inexpensive - Electrical insulator - Flexible
54
What is a common use of poly(chloroethane), PVC, and what properties make it suitable for this use?
Use for window frame because it is tough, cheap and a long product life.
55
What is a common use of poly(tetrafluoroethene), PTFE, and what properties make it suitable for this use?
Coating for non-stick pans because it is tough and non-stick.
56
By what process are polyesters formed?
Condensation polymerisation.
57
Why are polyesters condensation polymers?
Because a small molecule (water) is released when the bond is formed between two monomers.
58
What reactants are required to form a polyester?
Molecules with two carboxylic acid groups (-COOH) and molecules with two alcohol groups (-OH).
59
Describe the formation of an ester bond?
The carboxylic acid loses an OH from the COOH group. The alcohol loses a H from the -OH group. The two larger molecules combine, forming an ester bond. The OH and H+ molecules lost during the bond formation combine to make water.
60
What are some of problems associated with polymers?
- Crude oil (starting material) is a finite resource. - Not biodegradable so take up space in landfill and end up in the oceans, causing problems for marine life. - Produce carbon dioxide if incinerated (and HCl is the polymer contain chlorine). - Production process requires a lot of energy. - Recycling requires careful sorting which is time-consuming.
61
What are the advantages associated with recycling polymers?
- Provides employment. - Less crude oil used. - Less energy used in recycling than in processing new materials. - Reduces the amount of space needed for landfill and fewer polymers end up in the ocean.
62
What are the disadvantages associated with recycling polymers?
- Labour intensive and expensive to first separate the polymer into different recycling categories. - Melting polymers produces toxic gases which are harmful for animals and plants. - Polymers can only be recycled a certain number of times before losing their properties and becoming unusable.
63
What is starch?
A polymer based on sugars.
64
In terms of polymers, what is DNA?
A polymer made from four different monomers called nucleotides.
65
What are proteins?
Polymers based on amino acids.
66
What functional group do alcohols contain?
-OH
67
What are the names and formulae of the first four alcohols?
Methanol (CH3O) Ethanol (C2H5OH) Propanol (С3Н7ОН) Butanol (C4H9OH)
68
How is boiling point affected by an alcohol's chain length?
As the chain length of an alcohol increases, boiling point increases.
69
How can an alkene be produced from an alcohol?
During a dehydration reaction with sulfuric acid. Water is also produced.
70
What functional group do carboxylic acids contain?
-COOH
71
What are the names and formulae of the first four carboxylic acids?
Methanoic acid (HCOOH) Ethanoic acid (СН3СООН) Propanoic acid (C2H5СООН) Butanoic acid (С3H7СООН)
72
How can ethanol be converted into ethanoic acid?
Oxidation
73
Butanol is oxidised. What is the product?
Butanoic acid
74
Why do members of the same homologous series undergo similar reactions?
The molecules have the same functional group so have similar chemical properties.
75
Which renewable process can be used to produce ethanol?
By fermentation of carbohydrates in aqueous solution with yeast (provides enzymes).
76
What conditions are required for the fermentation of glucose to form ethanol?
- Anaerobic conditions (no oxygen). - Warm to increase rate of reaction without denaturing enzymes in the yeast.
77
What is the word equation for the fermentation of glucose?
Glucose → ethanol + carbon dioxide
78
How can pure concentrated ethanol be extracted from the fermentation mixture?
Fractional distillation. Ethanol has a lower boiling point than water so will evaporate first.
79
Compare the size of nanoparticles to atoms and molecules?
Nanoparticles contain a few hundred atoms and are between 1-100 nm (nanometres) across.
80
What are some of the risks associated with nanoparticulate materials?
- Little is known about the effects of nanoparticles. - May be harmful to health (they could enter the bloodstream or be breathed in). - May catalyse harmful reactions inside the body. - Large surface area to volume ratio may allow toxic substances to bind to them and enter the body.
81
Why would nanoparticles be useful catalysts?
Nanoparticles have a very high surface area to volume ratio.
82
83
Why might nanotubes be used to make electrical circuits for computers?
- Can conduct electricity. - Are very small so take up little space. - Lightweight.
84
Why might nanoparticles be used in sunscreen?
Some nanoparticles block UV light. Nanoparticles don't leave white marks on skin.
85
What are the general properties of glass ceramics?
- Transparent. - Strong but brittle. - Easily moulded into shapes. - Poor conductors.
86
What are the general properties of clay ceramics?
- Opaque. - Soft and malleable. - Hardened with heat. - Brittle once hardened. - Poor conductors.
87
What are the general properties of polymers?
- Properties can be adapted to suit the purpose. - Usually tough and flexible. - Can be transparent or opaque. - Poor conductors.
88
What are the general properties of metals?
- Shiny - Malleable - Ductile - Good conductors - Can form alloys to produce more desirable properties.
89
What is a composite material?
Contains two or more materials with different properties.
90
Why do composite materials have a wide range of different properties?
As composite materials are made of several materials, the properties can be tailored to suit the need of the composite. Different composite materials contain different reinforcements and matrixes so the properties vary.

Chemistry (11 decks)

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