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chemistry igcse draft > harder questions > Flashcards

harder questions Flashcards

1
Q

give two reasons why the electrolysis is carried out on aluminium oxide dissolved in molten cryolite instead of electrolysing molten aluminium oxide only

A

imrpoves conductivity of the electrolyte
lower operating temp

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2
Q

what is meant by term amphoteric

A

neutralises both acids and bases

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3
Q

what is the substance that reacts with oleum to form sulfuric acid

A

water

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4
Q

Name the black solid that is produced when concentrated sulfuric acid is added to sugar,
C12H22O11.

A

carbon

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5
Q

Name the type of reaction in which proteins are broken down into amino acids

A

hydrolysis

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6
Q

Name two types of substance that are used to break down proteins into amino acids

A

enzymes and acids

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7
Q

Name the process used to separate the amino acids

A

chromotogrpahy

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8
Q

Name the type of substance used to detect the amino acids.

A

locating agent

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9
Q

Give the symbol of the value used to determine the identity of each amino acid after separation and detection

A

rf value

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10
Q

Name a synthetic polyamide.

A

nylon

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11
Q

Identify the two functional groups present in the monomers used to produce synthetic
polyamides.

A

carboxylic acid
amine

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12
Q

what isthe color of copper in electrolysis

A

pink/brown

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13
Q

why are carbon electrodes used

A

inert, conducts electricity

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14
Q

why is the universal indicator not fit for use in titration

A

too many colour changes

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15
Q

what happens when hydrogen peroxide reacts with manganese oxide catalyst

A

oxygen is produced

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16
Q

State what happens to the colour of the aqueous copper(II) sulfate as this electrolysis progresses.

A

becomes colourless solution

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17
Q

State one disadvantage, other than cost, of using hydrogen–oxygen fuel cells to power
cars compared to using petrol.

A

needs high pressure to store hydrogen

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18
Q

Name the substance used to remove sulfur dioxide in flue gas desulfurisation.

A

calcium oxide

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19
Q

State one use of ammonium sulfate.

A

fertiliser

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20
Q

general formula for carboxylic acids is

A

CnH2n+1COOH

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21
Q

how many water molecules are binded to hydrated copper sulfate

A

5
CuSO4 . 5H2O

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22
Q

how many water molecules are binded to hydrated cobalt chloride

A

6
CoCL2 . 6H2O

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23
Q

State the meaning of the Roman numeral after a compound

A

oxidation state

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24
Q

what is a suitable catalyst for the formation of an ester

A

acid

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25
Q

what element is stored under oil

A

potassium and sodium

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26
Q

what is found in the ore of zinc blende

A

sinc and sulfur

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27
Q

what happens when sucrose is dehydrated by concentrated sulfuric acid what is formed

A

carbon

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28
Q

test for chlorine and result

A

damp litmus paper turn s blue

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29
Q

explain why iron doesn’t rust even if zinc is scratched

A

zinc is more reactive than iron
zinc loses electrons / zinc is oxidised
electrons are transferred to iron / iron is not oxidised / iron does not lose electrons

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30
Q

what is the colour of nitrogen oxide

A

brown gas

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31
Q

type of particle responsible for the conduction of electricity during electrolysis in electrolyte

A

ions

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32
Q

which substance is used to bleach wood pulp

A

sulfur dioxide

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33
Q

what is used as a fuel in fuel cells

A

hydrogen

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34
Q

what catalyst is used in a catalytics converter

A

platinum

35
Q

how can Complex carbohydrates break down to form simple sugars.

A

acids
enzymes

36
Q

how do you form a polymer from a unit of glucose (OH)

A

remove the h, and only have O links

37
Q

When aqueous ammonia is added to aqueous iron(II) sulfate a green precipitate is seen, name precipitate

A

iron (ii) hydroxide

38
Q

suggest why the green ppt turns red near surface standing

A

iron (ii) hydroxide is oxidised by its reaction with air to form iron(iii) hydroxide

39
Q

suggest all particles responsible for the passage of electricity in molten copper(II) bromide

A

cuˆ2+
brˆ-

40
Q

Suggest the name of a metal which could be used as the inert electrodes.

A

platinum

41
Q

Suggest the change, if any, in the voltmeter reading if the zinc electrode was replaced with an iron electrode. Explain your answer.

A

voltage decreases because zinc is more reactive than iron

42
Q

The zinc electrode was replaced with a silver electrode. The reading on the voltmeter was
–0.46 V.
Suggest why the sign of the voltmeter reading became negative

A

silver is less reactive than copper

43
Q

in an electrolysis of concentrated sulphuric acid, electrodes one is made of copper and the other of zinc, what is the electron flow

A

from zinc to copper, because zinc is more reactive, more easily loses electrons

44
Q

what is an element

A

made of atoms with same atomic number
cant be broken down into simpler substances

45
Q

How would you show that an aqueous solution of ethanoic acid is an acid without using an indicator or measuring the pH?

A

react it with a metal eg. magnesium, would see effervesces and metal dissolving

46
Q

metal oxides are acidic or basic give examples

A

basic
cuO and CaO

47
Q

non metal oxides are acidic or basic give examples

A

acidic eg. CO2 and SO2

48
Q

amphoteric acids meaning and give examples

A

neutralise both acids and bases
ZnO and Al2O3

49
Q

what salts are soluble

A

all sodium potassium ammonium and all nitrates
all chlorides except silver and lead
al iodine and bromide accept silver
all sulfates except, lead, calcium and barium

50
Q

what salts are insoluble

A

all carbonates except- sodium potassium ammonium
all hydroxides except- sodium potassium ammonium
silver chloride, lead chloride, silver bromide, silver iodide, barium sulfate, calcium sulfate, lead sulfate

51
Q

what is the order of the fractional distillation of petroleum

A

refinery gas
petrol
naptha
kerosene
diesel oil
lubricating oil
fuel oil
bitumen

52
Q

conditions needed in a catalytic converter

A

high temperature and platinum catalyst

53
Q

conditions needed in cracking

A

ceramic catalyst and high temp

54
Q

conditions needed in esterification

A

acid (inorganic) catalyst

55
Q

what are the golden five

A

nitrate- NO3 -
carbonate- CO3 2-
hydroxide- OH-
sulphate- SO4 2-
ammonium- NH4 +

56
Q

ammonia gas formula

A

NH3

57
Q

how is sulfuric acid formed from sulfur trioxide

A

sukfur trioxide reacts with sulfuric acid froming oleum
oleum reacts with water to form sulfuric acid

58
Q

how does burning sulfur ores cause acid rain

A

produces sulfur dioxide, which reacts with water from rain

59
Q

what is PET also known as

A

terylene

60
Q

how do you find percentage yield

A

find number of moles of each compound, (remember to remove ratio) and then divide the reactant by the product moles and times by 100%

61
Q

what are the trends of the group 2

A

alkali metals- soft metals, low densities and low melting points
going down group:
increase density
increase reactivity
decrease melting point

62
Q

what are the trends of group 7

A

halogens- diatomic atoms
going down group:
increase density
increase melting point
decrease reactivity

63
Q

charge of silver

A

+1

64
Q

how do you convert an alkene to an alkane

A

you add hydrogen

65
Q

what reagents are needed to convert an alkene to ethanol (as the only product)

A

steam

66
Q

whats the type of reaction that occurs when an alkene is converted to ethanol as the only product

A

addition

67
Q

Explain, in terms of attractive forces between particles, why LiCl is a solid at room temperature but NCl 3 is a liquid with a relatively low boiling point.

A

licl has ionic bonds
attraction between molecules in NCl3 have weak attraction (weak intermolecular forces)
take more energy to break strong ionic bonds

68
Q

what does fluorine look in room temp

A

yellow pale gas

69
Q

Describe how you would make a sample of limewater starting with solid calcium hydroxide

A

add excess calcium hydroxide to water, then filter

70
Q

Some sulfur is obtained by mining.
Name one other major source of sulfur

A

fossil fuels or petroleum

71
Q

State and explain the effect of increasing the pressure on the rate of the forward reaction

A

more particles per unit volume
rate increases
more collisions per sec

72
Q

what happens when a highly reactive metal nitrate thermally decomposes

A

(potassium sodium and calcium)
metal nitrate + oxygen
2metalNO3(s) -> 2metalNO2(s) + O2(g)

73
Q

what happens when a mild reactive metal nitrate thermally decomposes

A

( magnesium, aluminum, zinc, iron, copper)
metal oxide + nitrogen dioxide + oxygen
2metal(nitrate) -> metalO(s)+ NO2(g) +O2(g)

74
Q

what happens when a weak reactive metal nitrate thermally decomposes

A

(silver and gold)
metal + nitrogen dioxide + oxygen
metal nirate(s)-> metal(s) NO2(g) + O2(g)

75
Q

what is the rule for metal carbonates and thermal decompositon? and what are the products

A

only mildly reactive metals react with heat
forms:
metal oxide + carbon dioxide

76
Q

what is the rule for metal oxides and thermal decompositon? and what are the products

A

only low reactive metals react with heat to form:
metal + oxygen

77
Q

what is the colour of solution during electrolysis of copper sulfate using carbon electrodes

A

solution colour fades
because copper ions are removed and not replaced

78
Q

what is the colour of solution during electrolysis of copper sulfate using copper electrodes

A

colour remains the same
because copper ions are removed but alos replaced

79
Q

which element is used as a food preservative

A

sulfur dioxide

80
Q

what happens when weak metal carbonates thermal decompose

A

forms metal +carbon dioxide + oxygen

81
Q

Explain why the rate of reaction is highest at the start of the reaction.

A

collision frequency is highest at the start, bigger concentration of reactants at the start of the reaction

82
Q

Explain, in terms of bonding, why sodium oxide has a high melting point.

A

positive ions and negative ions
strong attraction / strong bonds

83
Q

State one advantage of using hydrogen–oxygen fuel cells instead of petrol in vehicle engines.

A

no co2 involved
more efficient

chemistry igcse draft (16 decks)

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