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BTEC Unit 5 > Chemistry > Flashcards

Chemistry Flashcards

1
Q

What are the pH of acids?

A

Acids = 0 - 6

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2
Q

What are the pH of bases?

A

Bases = 8 - 14

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3
Q

Are metal hydroxides acids or alkalis/bases?

A

Bases

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4
Q

Are metal carbonates acids or alkalis/bases?

A

Alkali/bases

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5
Q

Are metal oxides acids or alkalis/bases?

A

Alkali/bases

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6
Q

What is the difference between an alkali a base

A

Bases are solid, alkalis are soluable bases

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7
Q

Define amphoteric

A

Can act as an acid and a base

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8
Q

What is a general equation for a neutralisation reaction?

A

Acid + Alkali –> Salt + Water

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9
Q

Write balanced symbol equations for the neutralisation reactions between hydrochloric acid and sodium hydroxide.

A

HCl + NaOH –> H₂O + NaCl

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10
Q

Acid is a ___ donor

A

Proton (H+)

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11
Q

Alkalis produce what ion in solution

A

OH-

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12
Q

Alkali is a ___ acceptor

A

H+

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13
Q

Acid creates ___ in water

A

H+

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14
Q

Bases ______ an acid

A

Neutralises

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15
Q

All alkalis are ___

A

Bases

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16
Q

What is a nucleophile?

A

An electron rich species, e.g. a species with a long pair or a negative charge

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17
Q

What is an electrophile?

A

An electron poor species, e.g. positively charged species

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18
Q

Outline the mechanism for the electrophillic addition of HBr to ethene

A
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19
Q

State uses for alumina (Al2O3)

A

The major uses of aluminium oxide is in refractories, ceramics, polishing and abrasive applications.

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20
Q

Describe what happens to ions (Al3+ and O2-) when Al2O3 is electrolysed

A

Al3+ gains electrons and forms pure Aluminium (Reduction), O2- looses electrons and forms Oxygen gas (Oxidation)

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21
Q

State half equations for the reactions at the electrodes

A

Anode) 2O2- —> O2 + 4e- Cathode) Al3+ + 3e- —> Al

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22
Q

Describe the reactions at the electrodes as oxidation/reduction

A

The reaction at the anode is Oxidation (losing electrons), and the reaction at the cathode is Reduction (gaining electrons)

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23
Q

Explain why electrolysis of alumina is expensive

A

It’s expensive due to the large amount of electricity required to keep the alumina (bauxite) molten to allow the electrolysis to continue 24/7, 365

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24
Q

State uses of titanium

A

Titanium metal is used as an alloying agent with other metals (e.g. aluminium). Alloys of titanium are used in aerospace, aircraft and engines due to the strong, lightweight, temperature-resistant properties.

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25
Q

Describe the steps in the Kroll process

A

Step 1) Titanium (IV) dioxide, coke (form of carbon) and chlorine are heated together at 900c to form Titanium (IV) chloride. TiO2(s) + 2C(s) + 2Cl2(g) —> TiCl4(g) + 2CO(g) Step 2) Magnesium is used as a reducing agent, which reacts with the chlorine to remove it from the titanium, forming pure titanium metal, and magnesium chloride liquid. TiCl4(g) + 2Mg(s) —> Ti(s) + 2MgCl2(l)

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26
Q

Explain why the Kroll process is expensive

A

The process required very high temperatures to break the strong bonds in titanium. It’s very labour intensive. Magnesium (or other metals used) is a very expensive metal, and is used in large quantities to obtain the pure titanium.

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27
Q

State the definition of a transition metal

A

forms one or more stable ions which has incompletely filled d orbitals

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28
Q

State characteristics of transition metals

A

-have an incomplete D subshell -have variable oxidation states -forms complex ions -catalysts -coloured componds

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29
Q

State what a complex ion is

A

Complex ion - a positively charged ion that is surrounded by a number of molecules that are oppositely charged.

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30
Q

State what a dative bond is

A

Dative bond - when both electrons are donated by one molecule to form a covalent bond.

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31
Q

State what a ligand is

A

Ligand - a molecule with a lone pair of electrons e.g. water or ammonia.

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32
Q

State what a catalyst is

A

Catalyst - speeds up chemical reactions

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33
Q

State how a catalyst affects the rate of a reaction

A

catalyst lowers the activation energy by providing a different pathway

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34
Q

Explain why transition metals make good catalysts

A

-variable oxidation rates -can be oxidised and reduced (change their oxidation state) -lower thr activation energy by providing an alternitive route

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35
Q

Explain why transition metals form complex ions

A

They are small with high charge to size ratios. They have empty ‘s’ and ‘d’ orbitals to accept lone pairs from ligands.

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36
Q

Describe the stages of the Contact Process

A

Stage 1: sulfur dioxide is made (mixed with excess air) Stage 2: sulphur trioxide is made SO2 + V2O5 = SO3 + V2O4 Stage 3:sulphur trioxide is converted into sulphuric acid V2O4 + 0.5 O2 = V2O5

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37
Q

Describe the use of Iron in the Haber process

A

It makes ammonia.

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38
Q

Whats is left in the solution in the ectrolysis of brine

A

Na+ and OH- from thr water are left in the soloution, this forms sodioum hydroxide

39
Q

What are uses of sodium hydroxide?

A

the purification of bauxite to make aluminium oxide (alumina) as a part of the manufacture of aluminium making paper - the sodium hydroxide helps break the wood down into pulp making soap - sodium hydroxide reacts with animal and vegetabl fats and oils to make compounds, such as sodium stearate, that are present in soap making bleach - bleach is formed when sodium hydroxide and chlorine react together in the cold; it is a mixture of sodium chlordie and sodium chlorate (I) solution (NaClO)

40
Q

In a diaphragn cell why can brine pass from one side to the other but gases can’t?

A

The diaghragm dividing the cell is porous

41
Q

How is the sodium chloride separated from sodium hydroxide in a diaphragm cell?

A

It is crystallised (less soluble)

42
Q

In a membrane cell why can only sodium ions move from one side to the other?

A

The divider is an ion-exchange membrane that only allows positive ions through

43
Q

How is sodium hydroxide separated from sodium chloride in the membrane cell?

A

It is already separated as sodium hydroxide is left on the cathode side

44
Q

What are the pros and conds of diaphragm cell?

A

Pros: cheap Cons: diaphragm needs replacing regularly, impure NaOH is made and uses slightly more energy

45
Q

What are the pros and cons of membrane cell?

A

Pros: Membrane needs little maintenance, pure NaOH formed, slightly less energy Cons: expensive

46
Q

State uses for the products formed from the electrolysis of brine

A

Chlorine used as disinfectant and purifier, manufacture of hydrochloric acid and making plastics. Sodium Hydroxide used for processing food products, removing pollutants from water and manufacture of paper. Hydrogen used in the manufacture of hydrochloric acid and potential as a pollution-free fuel

47
Q

Describe the movement of ions during the electrolysis of brine

A

Sodium ions will move to the negative electrode (anode) and chloride ions will move to the positive electrode (cathode)

48
Q

What is produced at the positive electrode for the electrolysis of brine?

A

Chlorine gas

49
Q

What is produced at the negative electrode for the electrolysis of brine?

A

Hydrogen gas

50
Q

Why is hydrogen produced at the negative electrode in the electrolysis of brine and not Sodium?

A

Sodium is more reactive than hydrogen so will prefer to lose an electron rather than gain

51
Q

Write half equations for the reactions at each electrode in the electrolysis of brine

A

Cathode: 2Cl- –> Cl2 + 2e- Anode: 2H+ + 2e- –> H2

52
Q

Describe the reactions at the elctrodes in the electrolysis of brine as oxidation/reduction

A

Cathode: Chloride ions are oxidised (oxidation is loss) Anode: Hydrogen ions are reduced (reduction is gain)

53
Q

State the general formula for alkanes?

A

CnH2n+2

54
Q

What is the molecular formula for methane?

A

CH4

55
Q

What is the molecular formula for butane?

A

C4H10

56
Q

What is the structural formula for hexane?

A
57
Q

Name the following:

A

2-methyl-propane

58
Q

Draw a dash/wedge diagram for methane

A
59
Q

What is the general formula for alkenes?

A

CnH2n

60
Q

Why are alkenes unsaturated compounds?

A

Because they have double bonds between carbon atoms

61
Q

Name the following compound

A

propene

62
Q

Draw the structural displayed formula for hex-2-ene

A
63
Q

Draw the structural formula of cyclopentane

A
64
Q

What is a structural isomer?

A

Same molecular formular but different structural formula (arrangement of bonds)

65
Q

What is a stereoisomer?

A

Same molecular formula but different arrangement of atoms in space

66
Q

Is this cis (Z) or trans (E)

A

cis (Z)

67
Q

Is this cis (Z) or trans (E)

A

trans

68
Q

Why does the boiling point of alkanes/alkenes increase with increasing chain length?

A

Increased surface area, more (stronger) intermolecular forces between chains and therefore more energy required to break them

69
Q

Why is the boiling point of branched alkanes lower than that of unbranched?

A

Branched alkanes cannot pack as closely together and therefore the intermolecular forces are weaker and require less energy to break.

70
Q

What are the products of complete combustion?

A

carbon dioxide + water

71
Q

Complete word & symbol equations for combustion of octane

A

word: octane + oxygen –> cardon dioxide + water symbol: C8H18(l) + 12.5 O2(g) –> 8CO2(g) + 9H2O(l)

72
Q

State the conditions required for free radical substitution reaction

A

UV light

73
Q

Name three steps in free radical substitution reactions

A

Initiation, Propagation and termination

74
Q

Describe the three steps in free radical substitution reactions

A

Initiation - homolytic bond fission of a halogen to form 2 halogen free radicals. ( 2 radicals after arrow) Propogation - steps where one free radical reacts and forms a different free radical. ( 1 radical before arrow, 1 after) Termination - combination of any two free radicals to form a stable product. ( 2 radicals before arrow)

75
Q

Write equations for the three steps of free radical substitution reactions for a given reaction E.g C2H6 + Br2 → C2H5Br + HBr

A

Initiation - Br2 → 2Br• Propagation - C2H6+ Br• → •C2H5 + HBr •C2H5 + Br2 → C2H5Br + Br• Termination - 2Br• → Br2 2•C2H5 → C4H10 •C2H5 + Br• → C2H5Br

76
Q

Explain why there are multiple products of a free radical substitution reaction

A

Because its a cahin reaction

77
Q

Outline the steps of free radical substitution reaction for polymers

A

Initioation: no radicals –> 2 radicals e.g: Br2 –> 2Br• Propagation: Radical + no radical –> Radical + no radical e.g: C2H6 + Br• –> •C2H5 + HBr •C2H5 + Br2 –> C2H5Br + Br• Termination: Radical + non radical –> no radicals e.g: 2Br• –> Br2

78
Q

Explain the importance of cracking alkanes

A

To make smaller, higher demand alkanes.

79
Q

Does the diagram show an endothermic or exothermic reaction?

A

Exothermic

80
Q

Does the diagram show an endothermic or exothermic reaction?

A

Endothermic

81
Q

Which type of reaction leads to energy being dissipated to the surroundings?

A

Exothermic

82
Q

Which type of reaction absorbs energy from the surroundings?

A

Endothermic

83
Q

For which type of reaction would you observe a drop in temperature?

A

Endothermic

84
Q

For which type of reaction would I observe an increase in temperature?

A

Exothermic

85
Q

What is the definition of enthalpy?

A

The amount of energy transferred per amount of substance

86
Q

What is the unit for enthalpy?

A

J/mol or kJ/mol

87
Q

What is the equation for calculating energy change?

A

Energy transferred = mass x Specific Heat Capacity x temperature change

88
Q

For a endothermic reaction would enthalpy change be negative or positive?

A

Positive

89
Q

For a exothermic recation would enthalpy change be negative or positive?

A

Negative

90
Q

Define enthalpy of formation

A

The energy change when one mole of substance is made from its elements in their standard form under standard conditions

91
Q

Define enthalpy of combustion

A

Energy change when one mole of substance burns completely in oxygen under standard conditions

92
Q

Define enthalpy of neutralisatin

A

the enthalpy change when solutions of an acid and an alkali react together under standard conditions to produce 1 mole of water.

93
Q

Define Hess’ Law

A

The enthalpy change for any reaction is independent of the route taken

BTEC Unit 5 (3 decks)

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