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chemistry paper 2 Flashcards

1
Q

why do giant ionic structures have high melting and boiling points?

A

1- the ions are held together in a closely pack 3D lattice arrangement by the attraction between the oppositely charged ions
2- the electrostatic attraction between oppositely charged ions is very strong- a lot of energy is needed to overcome the strong attraction so ionic compounds have high melting and boiling points

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2
Q

how do the charges affect the strength of ionic bonding?

A

higher charge ions have stronger forces of attraction between them so have higher melting and boiling points

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3
Q

draw the structure of sodium chloride

A

Na+ and Cl- alternate

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4
Q

describe the bonding in diamond and draw its structure

A
  • each carbon atom forms 4 covalent bonds in a very rigid giant covalent structure.
  • this structure makes diamond the hardest natural substance- used for drill tips and cutting tools
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5
Q

describe the bonding in graphite and draw its structure

A
  • each carbon atom forms 3 covalent bonds, creating layers which are free to slide over each other.
  • this makes graphite useful as a lubricant
  • also leaves free electrons so graphite is the only non-metal which is a good conductor of electricity
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6
Q

what’s the equation for percentage yield?

A

percentage yield= actual yield (g)/ theoretical yeild (g) x 100

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7
Q

what is the number 6.023 x 10^23 called?

A

Avogadro’s number or the Avogadro constant

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8
Q

what is Avogadro’s law?

A

one mole of any gas always occupies 24 dm^3 at room temperature and pressure (25 ‘C and 1 atmosphere)

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9
Q

volume (dm^3) =

A

moles of gas x 24 = mass of gas/Mr of gas x 24

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10
Q

how do you calculate volumes in reactions if you know the masses?

A

1) find the reacting mass

2) convert the mass into a volume using vol=moles x 24

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11
Q

what forms in the electrolysis of aqueous solutions?

A

ions from the ionic compound, hydrogen ions H+ and hydroxide ions OH- from the water

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12
Q

what happens at the cathode of the electrolysis of aqueous solutions?

A

if H+ ions and metal ions are present, hydrogen gas will be produced if the metal ions are more reactive than the H+ ions. If the metal ions are less reactive than the H+ ions then a solid layer of pure metal will be produced instead

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13
Q

what happens at the anode of the electrolysis of aqueous solutions?

A

if OH- and halide ions (Cl-, Br-, I-) are present, molecules of chlorine, bromine or iodine will be formed. If no halide ions are present, the oxygen will be formed

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14
Q

what does a solution of sulfuric acid (H2SO4) contain?

A

3 different ions: SO4^2-, H+ and OH-

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15
Q

what happens at the cathode of the electrolysis of sulfuric acid?

A

hydrogen ions from the water or sulfuric acid accept electrons, so at the cathode hydrogen gas is produced
2H+ + 2e- –> H2

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16
Q

what happens at the anode of the electrolysis of sulfuric acid?

A

hydroxide ions lose electrons more easily than sulfate ions, so at the anode oxygen and water are produced

4OH- —> O2 + 2H2O + 4e-

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17
Q

what does a solution of sodium chloride (NaCl) contain?

A

4 different ions: Na+, Cl-, OH- and H+

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18
Q

what happens at the cathode of the electrolysis of sodium chloride?

A

hydrogen ions accept electrons more easily than sodium ions, so at the cathode, hydrogen gas is produced

2H+ +2e- –> H2

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19
Q

what happens at the anode of the electrolysis of sodium chloride?

A

chloride ions lose electrons more easily than hydroxide ions, so at the anode chlorine gas is produced

2Cl- –>Cl2 + 2e-

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20
Q

what does a solution of copper (ll) sulfate (CuSO4) contain?

A

4 different ions: Cu^2+, SO4 ^2-, H+ and OH-

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21
Q

what happens at the cathode of the electrolysis of copper (ll) sulfate?

A

copper ions accept electrons more easily than hydrogen ions, so at the cathode, copper metal is produced

Cu^2+ + 2e- –> Cu

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22
Q

what happens at the anode of the electrolysis of copper (ll) sulfate?

A

hydroxide ions lose electrons more easily than sulfate ions, so at the anode oxygen and water are produced

4OH- –> O2 + 2H2O + 4e-

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23
Q

how does the number of electrons transferred increase?

A

with time and current

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24
Q

what is the amount of product made by electrolysis depend on?

A

the number of electrons that are transferred

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25
Q

what does one amp flowing for one second mean?

A

a charge of one coulomb has movec

26
Q

charge=

A

current x time

27
Q

what’s one faraday?

A

96000 coulombs

28
Q

what does one faraday F contain?

A

one mole of electrons

29
Q

how do you convert coulombs to faradays?

A

divide coulombs by 96000

30
Q

how many moles of electrons to make one mole of atoms with a 1+ charge?

A

1 mole of electrons (1 faraday)

31
Q

how many moles of electrons to make one mole of atoms with a 2+ charge?

A

2 moles of electrons

32
Q

how many moles of electrons to make one mole of atoms with a 3+ charge?

A

3 moles of electrons

33
Q

what are the steps to find the mass of product produced when you are give time, current and reactant?

A

1) write out the balanced half-equation for electrode where the product is produced - cathode

2) calculate the no. of faradays:
coulombs= (amps x time (s) )
no. of faradays= coulombs/ 96000

3) calculate the number of moles of product produced:
divide the number of faradays by the number of electrons in the half-equation

4) write in the Mr values from the periodic table to work out the mass of product produced- mass = Mr x no. of moles

34
Q

why do atoms lose electrons more easily down group 1?

A

1) all group 1 metals have 1 electron in their outer shell
2) as you go down group 1, the outermost electron is in a shell that’s further from the nucleus.
3) which means the attraction between the outermost electron and the nucleus becomes less
4) so as you go down Group 1 the atoms get bigger, the outer electron is more easily lost and the metals are more reactive

35
Q

how can ethanol be produced from ethene and steam?

A

1) ethene is produced from crude oil by cracking
2) ethene (C2H4) will react with steamm (H2O) to make ethanol
3) needs a temp of 300’C and a pressure of 60-70 atmospheres
4) PHOSPHORIC ACID is used as a catalyst
5) cheap process as ethene is fairly cheap and not much is wasted
- but crude oil is non-renewable so will start running out soon- so will become an expensive process

36
Q

what’s the equation to make ethanol from steam and ethene?

A

C2H4 + H2O -> C2H5OH

37
Q

how can ethanol be produced by fermentation?

A

1) the raw material for fermentation is sugar e.g. glucose.This is converted into ethanol using yeast
2) this process needs a lower temperature about 30 and simpler equipment than using ethene
3) the raw materials are renewable resources- sugar and yeast are easy to grow
4) ethanol isn’t very concentrated so it needs to be distilled to increase its strength and purified.

38
Q

how can ethanol be dehydrated to form ethene?

A

1- remove water from the ethanol in a dehydration reaction
2) ethanol vapour is passed over a hot catalyst of aluminium oxide, Al2O3- the catalyst provides a large surface area for the reaction

39
Q

what’s a laboratory experiment set up fort the dehydration of ethanol to form ethene?

A
  • soak ceramic wool in ethanol and put at the bottom of a test tube.
  • in the centre of the test tube put aluminium oxide powder
  • put a bung in the tube attached with a delivery tube to a measuring cylinder using upward delivery through a water bath.
  • place a Bunsen burner beneath the aluminium catalyst in the tube
40
Q

what’s the chemical equation for the dehydration of ethanol?

A

C2H5OH –> C2H4 + H2O

41
Q

what is bond energy?

A

the amount of energy in a bond- each type of chemical bond has a particular bond energy associated with it

42
Q

enthalpy change=

A

Total energy absorbed to break bonds - Total energy released in making bonds
if it’s negative change then the reaction is exothermic

43
Q

how do you calculate the molar enthalpy change?

A

1- calculate the amount of energy transferred
2- fine how many moles of fuel produced this heat- mass of fuel burnt/ Mr
3- the heat produced by 1 mole o fuel = joules of energy produced/ moles (if it is an exothermic reaction then the joules of energy will be negative)

44
Q

draw chloroethene and poly(chloroethene)

A

CH2=CHCl and CH2- CHCl

45
Q

what’s condensation polymerisation?

A
  • involves two different types of monomer
  • the monomers react together and bonds form between them, making polymer chains
  • for each new bond that forms, a small molecule, e.g. water, is lost
46
Q

give an example of condensation polymerisation

A

nylon

draw two monomers -> condensation polymer + water

47
Q

what’s poly(chloroethene) used for?

A

making clothes, and pipes for insulating electrical cables

48
Q

what is the contact process?

A

it’s used to make sulfuric acid

49
Q

what are the 4 stages of the contact process?

A

1) first forming SULFUR DIOXIDE (SO2) gas- BURNING sulfur in air or roasting sulfide ores
S + O2 -> SO2
2) the sulfur dioxide is then OXIDISED with a catalyst, to form SULFUR TRIOXIDE (SO3)
2SO2 + O2 –> 2SO3
3) the sulfur trioxide is DISSOLVED in concentrated sulfuric acid to form liquid OLEUM
SO3 + H2SO4 –> H2S2O7
4)oleum is DILUTED with measure amounts of water to form concentrated sulfuric acid
H2S2O7 + H2O –> 2H2SO4

50
Q

What type of reaction is step two in the contact process?

A

exothermic-gives out heat- there are 2 moles of product compared to 3 moles of reactants so the product has less volume than the reactants

51
Q

how do you get maximum yield in the contact process?

A

reduce the temperature and increase the presuure but reducing temp slows down the reaction

52
Q

what are the conditions needed in the contact process?

A

1) TEMPERATURE: 450’C
2) PRESSURE: 2 atmospheres
3) CATALYST: Vanadium (V) oxide , V2O5

53
Q

what’s sulfuric acid used for in industry?

A

1- fertilisers- mostly used to make phosphate fertilisers- farmers use them to improve the amount of nutrients in the soil to increase plant growth
2- detergents- used for cleaning anything
3- paints- sulfuric acid is used to make TITANIUM DIOXIDE, which is a white PIGMENT that’s used in paints and white lines on tennis courts

54
Q

what is brine?

A

sodium chloride solution

55
Q

how is brine electrolysed industrially? and what does it produce?

A

using a diaphragm cell- 3 useful products: hydrogen gas, chlorine gas and sodium ions

56
Q

what happens at the cathode in the electrolysis of brine?

A

hydrogen gas is given off -2 hydrogen ions accept 2 electrons to become one hydrogen molecule

2H+ +2e- –> H2

57
Q

what happens at the anode in the electrolysis of brine?

A

chlorine gas is given off- two chloride ions (Cl-) lose their electrons and become one chlorine molecule

2Cl- –> Cl2 + 2e-

58
Q

what happens to the sodium ions in the electrolysis of brine?

A

they stay in solution and the hydroxide ions from the water are also left behind. this means that sodium hydroxide is left in the solution

59
Q

what’s chlorine used for?

A

to sterilise water supplies- chlorination. and to make bleach and HCl

60
Q

what’s hydrogen used for?

A

used in the Haber process and to change oils into fats for making margarine

61
Q

what’s sodium hydroxide used for?

A

very strong base and used widely in the chemical industry- to make soap, bleach and paper pulp

revision (16 decks)

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