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AS Level Chemistry > and some more > Flashcards

and some more Flashcards

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1
Q

What is the trend in atomic radius moving down group 2 and why?

A

> increases as we move down

>as extra energy level to one above

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2
Q

What is the trend in first ionisation energy of the

elements in group 2 and why?

A

> decreases as you go down
electron further away from nucleus
and more shielding

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3
Q

What is the trend in melting point moving down group 2

and why?

A

> all have high melting points
decreases as you go down because increased shielding and distance between nucleus and delocalised electron
Mg id exception

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4
Q

What is the trend in reactivity of group two elements as we move down the group.

A

increases as you go down because more shielding + electron is further away from nucleus

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5
Q

Which three group 2 metals react readily with cold water?

A

Ca, Sr, Ba

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6
Q

Which group two metal only reacts very slowly with cold water and which does not react with water?

A

Slowly – Mg

Not at all - Be

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7
Q

Write out two symbol equation.

One for the reaction of Mg with water and one for its reaction with steam.

A

Mg(s) + 2H2O(l) -> Mg(OH)2(s) + H2(g)

Mg(s) + H2O(g) -> MgO(s) + H2(g)

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8
Q

What is the general equation for the reactions of group two metals with water?

A

M(s) + 2H2O(l) à M(OH)2(aq) + H2(g)

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9
Q

What is the meaning of amphoteric, and which group two metal hydroxide is amphoteric?

A

Amphoteric – behaves as both an acid and a base.

Beryllium hydroxide is amphoteric

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10
Q

Other than Beryllium hydroxide, which is amphoteric, are all other metal two hydroxides acidic or basic?

A

basic

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11
Q

What is the trend in solubility of the group two hydroxides, moving down the group? Which two are insoluble, and which one is slightly soluble?

A

More soluble down the group

Insoluble - Be(OH)2 and Mg(OH)2

Only slightly soluble – Ca(OH)2

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12
Q

What is the trend in solubility of the group two sulfates, moving down the group? Which two are soluble, and which one is slightly soluble?

A

Less soluble down the group.

Soluble - BeSO4 and MgSO4

Slightly soluble – CaSO4

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13
Q

What is Mg(OH)2 used for in medicine?

A

As a suspension in water, is called milk of magnesia.
It is used as an antacid, to treat indigestion.
Used as a laxative.

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14
Q

What is Ca(OH)2 used for in agriculture?

A

Often called slaked lime.

Used to neutralise the acidity of soil.

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15
Q

What is acidified BaCl2 used for and why?

A

As a test for sulfate ions, because Barium chloride is soluble, but barium sulfate is not. A positive result is the formation of a thick, white precipitate. Acidification prevents the formation of other precipitates.

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16
Q

What is BaSO4 used for in medicine?

A

Barium is good at absorbing X-rays. When eaten as a part of a ‘barium meal’, they allow the outline of the gut to be seen on X-ray. Although Barium ions are toxic Barium sulfate is harmless, because it is insoluble.

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17
Q

How are metals usually found in the earth?

A

ore

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18
Q

What are ores?

A

An ore is a type of rock that contains sufficient metals that it is economical to extract the metal from the rock

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19
Q

In what form are metals usually found in ores?

A

Oxides and sulphides.

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20
Q

What is normally the first step in extraction of metals from sulphides?

A

Roasting in air to convert them into oxides.

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21
Q

Are metal ores oxidised or reduced during extraction?

A

oxidised

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22
Q

Why are carbon and carbon monoxide desirable reducing agents used in the extraction of metals.

A

cheap and easy

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23
Q

How is aluminium manufactured from purified bauxite?

A

It is dissolved in molten cryolite. It is then electrolysed at currents of up to 300 000 A It is a continuous process in which the heat is generated by the passage of current and the aluminium formed as a liquid is siphoned off.

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24
Q

What is the reducing agent in the reduction of Iron oxide in the blast furnace?

A

carbon monoxide

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25
Q

What metals are carbon and carbon monoxide used in the extraction of?

A

iron, manganese and copper

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26
Q

Why is carbon reduction not used in the extraction of titanium, aluminium and tungsten?

A

Aluminium – Higher in the reactivity series than carbon.

Titanium and Tungsten - form metal carbides with the carbon, which makes the metal brittle.

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27
Q

Why is aluminium oxide dissolved in molten cryolite before being electrolysed?

A

To lower the melting point.
Aluminium oxide = 2345K
Cryolite = 1240K

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28
Q

Why is the electrolysis of aluminium oxide mainly done in countries with cheap electricity?

A

Because the main cost of the process is electricity.

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29
Q

How is titanium (IV) chloride reduced to pure sodium?

A

It is reduced with molten sodium (or magnesium) in an inert argon atmosphere at 1300K. (The Argon prevents the metals from reacting with N2 or O2 in the air).

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30
Q

Why are batch process like those used in the extraction of titanium less efficient than continuous processes?

A

Because the reaction vessels have to be heated back up to operating temperatures after each batch is removed.

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31
Q

What are the advantages of extracting copper by spraying it with dilute acid in the presence of the bacteria Thiobacillus ferrooxidans compared to high temperature reduction with carbon?

A

> Cheap scrap iron can be used
(the price of copper is much higher than the price of iron).
The process works on low grade ores.
No CO2 is produced during the extraction.

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32
Q

Why do the carbon electrodes used in the extraction of aluminium need to be replaced regularly?

A

The oxygen produced burns the carbon electrodes away to carbon dioxide.

33
Q

How is Titanium (IV) oxide converted to pure Titanium (IV) chloride?

A

It is reacted with coke and chlorine at a temperature of 1173K. The titanium (IV) chloride is then purified by distillation.

34
Q

What are the two steps involved in the extraction of titanium?

A

> First titanium (IV) oxide is converted to titanium (IV) chloride by reaction with coke and chlorine.

> Then it is converted from Titanium (IV) chloride to Titanium by reduction with sodium.

35
Q

What are the advantages of recycling scrap metals, compared with the extraction of metals?

A

Reduces waste to landfill, far less energy and resources needed.

36
Q

What sort of reaction is the reaction between methane and chlorine?

A

Free-radical substitution

37
Q

Give the three possible termination steps that happen in the reaction between methane and chlorine in the presence of UV light

A

Cl* + Cl* -> Cl2
CH3* + Cl* -> CH3Cl
CH3* + CH3* -> CH3CH3

38
Q

What are chloroalkanes and chlorofluroalkanes used as?

A

Solvents

39
Q

What was the Montreal protocol?

A

Legislation, supported by chemists, that ban the use of CFCs.

40
Q

Do haloalkanes contain polar bonds?

A

Yes

41
Q

What name is given to C2H5NH2?

A

Ethylamine

42
Q

Give the two propagation steps involved in the reaction between methane and chlorine in the presence of uv light.

A

CH4 + Cl* -> CH3* + ClH

CH3* + Cl2 -> CHCl + Cl*

43
Q

Why is ozone, formed in the upper atmosphere, beneficial?

A

It protects the earth from harmful exposure to too many ultraviolet rays. These rays are harmful to plankton and cause skin cancer.

44
Q

What do we now use instead of CFCs?

A

Alternative, chlorine free compounds.

45
Q

By reaction with OH- NH3 and CN- primary haloalkanes can be converted into what?

A

OH- = primary alcohol
NH3 = primary amine
CN- = Nitrile

46
Q

What can primary amines, alcohols and nitriles be converted into?

A

Primary amine -> Secondary amine -> tertiary amine Primary Alcohol -> aldehyde -> carboxylic acid
Nitrile -> Primary amine or carboxylic acid.

47
Q

What factors determine how readily a C-X bond breaks?

A

The bond polarity (The more polar the more easily broken). AND The bond enthalpy (the lower the more easily broken).

48
Q

What shape is >C=C

A

planar

49
Q

How can we test for unsaturation (a C=C bond)?

A

Add bromine water, which will change from brown (the colour of bromine) to colourless (the colour of the products.

50
Q

Where is the area of high electron density in an alkene?

A

double bond

51
Q

What is the order of stability of carbocations?

A

Tertiary = most stable
Secondary = second most stable
Primary = least stable.

52
Q

What role does sulphuric acid play in the hydration of ethene to form ethanol.

A

catalyst

53
Q

Give some typical uses of poly(ethene).

A

Washing up bowls Plastic bags.

54
Q

Give some typical uses of poly(propene).

A

rope

55
Q

When HBr reacts with Propene, what would the vast majority of the product be and why?

A

2-bromopropane Because this is formed from a secondary carbocation, which is more stable than the primary carbocation that is also formed.

56
Q

What are the typical conditions used for the industrial production of ethanol from ethene?

A

Reaction with concentrated sulphuric acid at room temperature.

57
Q

What are the economic and environmental advantages and disadvantages of producing ethanol from fermentation rather than the hydration of ethene?

A

Disadvantages of fermentation – it is a batch process and is slower. The product is an aqueous solution of ethanol and is less pure than that produced by the hydration of ethene. Advantages of fermentation – raw materials are sustainable. Low carbon process that could one day be carbon neutral.

58
Q

What is the meaning of the phrase ‘carbon neutral’?

A

An activity that has no net annual carbon emissions to the atmosphere.

59
Q

What are primary alcoholsoxidised to, and what is the

product of further oxidation?

A

Primary alcohol +[O] -> aldehyde + [O] -> Carboxilic acid

60
Q

How is ethanol produced industrially by fermentation?

A

Glucose is fermented in the presence of yeast at 35OC, anaerobically, to prevent oxidation of the ethanol to ethanoic acid.

Once the solution contains 15% ethanol the enzymes are unable to function and the reaction stops. Distillation is used to purify the ethanol.

61
Q

Give the equation for the fermentation of glucose to form ethanol.

A

C6H12O6(aq) -> 2C2H5OH(aq) + 2CO2(g)

62
Q

What is the meaning of the term biofuel?

A

A fuel derived or produced from renewable biological sources.

63
Q

Why might some people consider ethanol produced by fermentation carbon neutral, and why might some people not?

A

Carbon neutral – Crops take in carbon dioxide when they grow, so there is no net increase in CO2 in the atmosphere when they are burnt.

Not Carbon neutral – Transport, farming and fertilisers all rely on the use of non carbon neutral fuels.

64
Q

Suggest a suitable oxidising agent that could be used to oxidise alcohols and aldehydes in the lab.

A

Acidified potassium dichromate(VI)

65
Q

Suggest suitable conditions for the dehydration of alcohols.

A

Aluminium oxide catalyst
600K
Or
Heat with hot sulphuric acid

66
Q

Suggest the mixture of alkenes that would be formed from the dehydration of butan-2-ol?

A

But-1-ene

Z-but-2-ene

E-but-2-ene

67
Q

How does the oxidation of aldehydes and ketones differ. Suggest a test that could be used to distinguish between them.

A

Aldehydes are oxidised to carboxylic acids. Ketones are not changed by gentle oxidation. So… Tollens silver mirror test produces a silver mirror on the side of a test tube with an aldehyde but there is no change with a ketone. Likewise Fehlings (Benedict’s solution) turns from blue to brick red with an aldehyde, but does not change with a ketone.

68
Q

What would be the products formed from the dehydration of propan-1-ol?

A

Propene and water

69
Q

Why is the dehydration of alcohols to form alkenes useful?

A

Because it provides an alternative route to polymers, rather than using monomers derived from oil.

70
Q

why can sulfuric acid not be used to acidify the barium ions

A

> contains sulfate ions

> and we are testing for sulfate ions

71
Q

what does rate of reaction mean

A

change in conc. of a substance over a specified amount of time

72
Q

what is barium sulfate used for in medicine

A

> Barium meals in X-Rays

> barium sulfate is insoluble

73
Q

SO2

A

colourless gas- ‘choking gas’ toxic

74
Q

S

A

yellow solid

75
Q

H2S

A

hydrogen sulfide

colourless gas ‘bad egg smell’ highly toxic

76
Q

Cl2 gas

A

pale green

77
Q

Br2 gas

A

brown fumes

78
Q

I2 gas

A

purple fumes

AS Level Chemistry (7 decks)

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