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CHEMISTRY -EVIE💘 > Topic 4- Chemical changes > Flashcards

Topic 4- Chemical changes Flashcards

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1
Q

what does the ph scale go from

A

0 to 14

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2
Q

what is the ph scale a measure of

A

how acidic or alkaline a solution is

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3
Q

the lower the ph…

A

the more acidic it is

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4
Q

the higher the ph….

A

the more alkaline it is

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5
Q

what pH does a neutral substance have (water)

A

7

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6
Q

whats an indicator

A

a dye which changes colour depending on whether its above or below a certain pH

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7
Q

what are wide range indicators

A

indicators that contain a mixture of dyes that means thry gradually change colour over a broad range of pH (universal indicator)

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8
Q

give an example of electronic indicating

A

a pH probe attatched to a pH meter is placed in the solution you are measuring and the pH is given on a digital display as a numerical value, meaning its mre accurate than an indicator

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9
Q

what ions do acids form in water

A

H+

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10
Q

whats an alkali

A

a base that dissolves in water to form a solution with a ph greater than 7

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11
Q

give the numbers on the pH scale for an acid

A

less than 7

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12
Q

give the numbers on the pH scale for a base

A

greater than 7

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13
Q

what ions do alkalis form

A

OH -

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14
Q

whats an acid

A

a substance that forms aqueous solutions will a pH of less than 7

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15
Q

whats the reaction between acids and bases called

A

neutralisation

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16
Q

give the word equation for acids and bases

A

acid + base -> salt + water

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17
Q

give the symbol equation for acids and bases

A

H+ (aq) + OH- (aq) -> H2O (l)

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18
Q

when acid neutralises a base

A

the products are neutral and at pH7

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19
Q

what can an indicator show

A

that a neutralisation is over

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20
Q

what does an acid and alkali produce

A

water

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21
Q

what do acids produce in water

A

protons (hydrogen ions)

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22
Q

what do acids do in aqueous solutions

A

ionise

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23
Q

whats a H+ ion also known as

A

a proton

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24
Q

what do strong acids do in water

A

ionise completely

all acid particles dissociate to release H+ ions

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25
Q

name some strong acids

A

sulfuric, hydrochloric, nitric acids

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26
Q

name some weak acids

A

ethanoic, citric and carbonic

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27
Q

what do weak acids do in a solution

A

do not fully ionise and only a small proportion of acid particles dissociate to release H+ ions

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28
Q

describe the ionisation of a weak acid

A

reversible reaction

sets up equilibrium between the undissociated and dissociated acid

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29
Q

why does the position of equilibrium lie on the left in the ionisation of weak acids

A

because only a few of the acid particles release H+ ions

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30
Q

what do reactions of acids involve

A

the H+ ions reacting with other substances

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31
Q

if the conc of H+ ions is higher…

A

the rate of reaction will be faster

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32
Q

which are more reactive, strong acids or weak acids?

A

strong will be more reactive than weak acids of the same concentration

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33
Q

whats pH a measure of in terms of ion s

A

the conc of hydrogen ions (H+) in a solution

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34
Q

describe the ratio between the ions and the pH scale

A

for every decrease of 1 on the pH scale, the conc of H+ ions increases by a factor of 10

for a decrease of 2 on the pH scale, the conc of H+ ions increases by a factor of 100

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35
Q

give the equation for the factor H+ ion concentration change

A

factor H+ ion concentration changes by = 10-x (to the power of)

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36
Q

whats x?

A

the difference in pH

so if pH falls from 7 to 4 the difference is 3- and the factor the H+ ion conc has increased by is 10- (-3) = 10(3)

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37
Q

what does acid strength tell you

A

what proportion of the acid molecules ionise in water

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38
Q

what does concentration tell you

A

measures how much acid their is in a certain volume of water (how watered down your acid is)

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39
Q

whats the relationship between amount of acid and concentration

A

the larger the amount of acid there is in a certain colume of liquid, the more concentrated the acid is

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40
Q

what will the pH do with acid, regardless of the acid strength

A

decrease with increasing acid conc

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41
Q

what are metal oxides and metal hydroxides

A

bases

42
Q

describe metal oxides and metal hydroxides

A

some dissolve in water
soluble
alkalis

43
Q

give the two equations for metal oxides and metal hydroxides

A

metal oxide + acid -> salt + water

metal hydroxide + acid -> salt + water

44
Q

what would sulfuric acid + potassium HYDROXIDE produce

A

potassium sulfate + water

H2SO4 + 2KOH -> K2SO4 + 2H20

45
Q

what are metal carbonates

A

bases

46
Q

give the equation for metal carbonates

A

acid + metal carbonate -> salt + water + carbon dioxide

47
Q

what would hydrochloric acid + sodium carbonate produce

A

sodium chloride + water + carbon dioxide

48
Q

you can make soluble salts using an..

A

insoluble base

49
Q

if you wanted to make copper chloride what could you mix

A

copper oxide and hydrochloric acid

50
Q

how do you make soluble salts from an insoluble base (practical)

A

1) gently warm dilute acid using bunsen burner, then turn off burner
2) add insoluble base to acid a bit at a time until no more reacts ( the base is in excess)
3) stop stiring when solid is sinking to to bottom (its excess)
4) filter out excess solid to get salt solution
5) to get the pure, solid crystals of salt, gently heat solution using a water bath or electric heater to evaporate some of the water ( make it more conc)
6) stop heating and leave to cool
7) crystals should form which can be filtered out of solution and then dried ( crystalisation)

51
Q

what does the reactivity series list

A

metals in order of their reactivity towards other metals

52
Q

what is a metals reactivity determined by

A

how easily they lose electrons to form positive ions

53
Q

the higher a metal is in the reactivity series…

A

the more easily it reacts with water or acid

54
Q

give the word equation for acid + metal

A

acid + metal -> salt + hydrogen

55
Q

whats the speed of a reaction indicated by

A

the rate at which the bubbles of hydrogen are given off

56
Q

the more reactive the metal….

A

the faster it will be

57
Q

how does magnesium react will cold dilute acids

A

vigorously, produces lots of bubbles

58
Q

how do zinc and iron react which dilute acids

A

slowly, but more strongly if you heat them up

59
Q

Fe + 2HCl -> ……

A

FeCl + H2

60
Q

how else can you investigate the reactivity of metals

A

by measuring the temperature change of the reaction with an acid or water over a set time period. if you use the same mass and surface area of metal each time, then the more reactive the metal, the greater the temp change should be

61
Q

give the word equation for metal + water

A

metal + water -> metal hydroxide + hydrogen

62
Q

Ca (s) + 2H20 (l) -> ….

A

Ca(OH)2 (aq)+ H2 (g)

63
Q

which metals will react with water

A

potassium, sodium, lithium, calcium

ZINC IRON AND COPPER WONT

64
Q

where do metals often have to be extracted from

A

their oxides

65
Q

whats a reaction where a metal is separated from its oxide called

A

a reduction reaction

66
Q

whats oxidation

A

gain of oxygen

e.g. magnesium is oxidised to make magnesium oxide 2Mg + O2 -> 2MgO

67
Q

whats reduction

A

loss of oxygen
e.g. copper oxide is reduced to copper
2Cu + C -> 2Cu + CO2

68
Q

how can zinc iron and copper be extracred from their ores

A

by reduction using carbon

69
Q

what happens in a reduction using carbon

A

the ore is reduced as oxygen is removed from it and carbon gains oxygen so is oxidised

70
Q

give an example of reduction using carbon

A

iron oxide + carbon -> iron + carbon dioxide

71
Q

how are potassium, sodium lithium calcium and magnesium extracted

A

using electrolysis

72
Q

why can zinc iron and copper be extracted by reduction using carbon

A

because theyre lower than carbon in the reactivity series

73
Q

give an example of a metal that is so unreactive its found in the earth as itself

A

gold

74
Q

whats a radox reaction,

A

where electrons are transferred

75
Q

describe oxidation and reduction in terms of electrons

A

loss of electrons- oxidation

gain of electrons- reduction

76
Q

when do reduction and oxidation happen

A

at the same time

77
Q

Al > Al3+ 3e- reduction or oxidation?

A

oxidation because Al has lost its electrons

78
Q

O + 2e- > O2- reduction or oxidation?

A

reduction because oxygen has gained electrons

79
Q

give the rule for displacement

A

a more reactive metal will displace a less reactive metal from its compound

80
Q

finish the equation

iron + copper sulfate ->

A

iron sulfate + copper

BECAUSE IRON IS MORE REACTIVE THAN COPPER

81
Q

for this reaction work out the two half equations…
Fe + CuSO4 > FeSO4 + Cu
iron + copper sulfate > iron sulfate + copper

A

Fe loses two electrons to become 2+
Cu gains two electrons to become 2-
Fe > Fe2+ 2e-
Cu2+ + 2e- > Cu

82
Q

whats oxidation

A

Gains Oxygen (as the name suggests)
Loses Hydrogen
Loses Electrons

83
Q

whats reduction

A

Loses Oxygen
Gains Hydrogen
Gains Electrons

84
Q

what does electrolysis mean

A

splitting up with electricity

85
Q

what happens in electrolysis

A

an electric current is passed through an electrolyte and the ions move towards the electrodes, where they react and the compound decomposes

86
Q

whats an electrolyte

A

a molten or dissolved ionic compound

87
Q

what happens to the positive ions in electrolysis

A

the positive ions in the electrolyte will move towards the cathode (-) and gain electrons
THEY ARE REDUCED

88
Q

what happens to the negative ions in electrolysis

A

the negative ions in the electrolyte will move towards the anode (+) and lose electrons

THEY ARE OXIDISED

89
Q

what does the movement of ions create

A

a flow of charge through the electrolyte as ions travel to the electrodes

90
Q

as ions gain or lose electrons…

A

they form the uncharged element and are discharged from the electrolyte

91
Q

why cant an ionic solid be electrolysed

A

because the ions are in fixed positions and cant move

92
Q

why can molten ionic compounds be electrolysed

A

because the ions can move freely and conduct electricity

93
Q

what do positive metal ions do at the cathode

A

they are reduced as they gain electrons

94
Q

what do negative non metals do at the anode

A

they are oxidised as they lose electrons

95
Q

describe the electrolysis which will take place with aluminium being extracted form bauxite…

A

1) aluminium has a very high m temp so its mixed with cryolite to lower the mpoint
2) the molten mixture contains free ions so it will conduct electricity
3) the positive Al3+ ions are attracted to the negative electrode where they each pick up three electrons and turn into neutral aluminium atoms
4) these then sink to the bottom of the electrolysis tank
5) the negative O2- ions are attracted to the positive electrode where they each lose two electrons. the neutral oxygen atoms will then combine to form O2 molecules

96
Q

give the two half equations for the aluminium oxide electrolysis example

A

Al3+ + 3e- > Al

2O2 > O2 + 4e-

97
Q

what do you have to factor in when electrolysing an aqueous solution

A

the ions in the water

98
Q

Electrolysis is very expensive because…

A

Melting the compounds such as aluminum oxide requires a lot of energy
A lot of energy is required to produce the electric current

99
Q

what ions are in aqueous solutions

A

H+

OH-

100
Q

what do you do to work out if chlorine hydrogen or oxygen are made

A

chloride bleaches litmus paper
hydrogen makes a squeaky pop with lighted splint
oxygen will relight a glowing splint

CHEMISTRY -EVIE💘 (9 decks)

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