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Paper1- Chemistry > Topic 4 - Chemical Changes > Flashcards

Topic 4 - Chemical Changes Flashcards

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1
Q

what is an acid

A

a proton ( H+) donor

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2
Q

what makes an acid an acid

A

the H+

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3
Q

what is an alkaline

A

a proton acceptor (OH-)

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4
Q

what makes an alkaline an alkaline

A

the OH-

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5
Q

what happens in a neuralisation reaction

A

an acid and alkali react together, the hydrogen ions react with hydroxide ions to produce water

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6
Q

what is the ionic equation for a neuralisation reaction between acid and alkali

A

H+ + OH- —> H2O

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7
Q

what is the word equation for the neutralisation of acid and alkali

A

acid + base —> salt + water

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8
Q

how do you find what volume of acid is needed to neutralise alkali

A

on a pH curve, find the pH 7 and draw a line across to the line then down to find the volume

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9
Q

what does the pH scale measure

A

a measure of the acidity or alkalinity of a solution

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10
Q

what does the pH scale go to

A

0-14

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11
Q

how can pH be measured

A

using universal indicator or pH probe

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12
Q

a solution with a pH of 7 is what?

A

neutral

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13
Q

what is the pH of acid

A

less than 7

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14
Q

what is the pH of alkaline

A

greater than 7

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15
Q

what is universal indicator

A

a dye that changes colour depending on pH

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16
Q

what is wide range indicator

A

contains a mixture of dyes that gradually change colour over a range of pH- its an estimate

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17
Q

what happens during a displacement reaction

A

the more reactive metal displaces the less reactive metal

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18
Q

what is shown in an ionic equation

A

only the particles that react and the products are shown

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19
Q

what is a spectator ion

A

they don’t change in the reaction

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20
Q

what is oxidation in terms of electrons

A

loss of electrons

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21
Q

what is reduction in terms of electrons

A

gain of electrons

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22
Q

what is the rhyme to remember oxidation and reduction in terms of electrons

A

Oxidation
Is
Loss
Reduction
Is
Gain

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23
Q

what is the half equation for zinc

A

Zn –> Zn 2+ + 2e-
oxidation half equation- zinc loses electrons

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24
Q

what happens to the metal ion and metal atom in a metal displacement reaction

A

the metal ion gains electrons- reduced
the metal atoms always loses electrons- oxidised

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25
Q

what is a metal ore

A

a rock containing enough metal or metal compound to make it worth extracting

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26
Q

what are native metals

A

found as the element because they are unreactive
eg platinum, gold, silver

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27
Q

what are most metals found as

A

compounds that require chemical reactions to extract

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28
Q

what are the stages of metal extraction

A
  1. mine the rock
  2. grind the rock to a powder
  3. separate metal compound from waste(chemicals)
  4. extract metal from compounds using reduction
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29
Q

how are metals less reactive than carbon extracted

A

can be extracted using carbon reduction in a blast furnace

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30
Q

why can carbon only be used to extract metals less reactive than them

A

carbon can only take oxygen from metals less reactive

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31
Q

what is an example of how iron reacts with carbon as a word equation

A

iron oxide + carbon –> iron + carbon dioxide

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32
Q

how are metals more reactive that carbon extracted

A
  • using electrolysis
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33
Q

what is the problem with using electrolysis

A

expensive

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34
Q

why are some metals and products more expensive

A

they cost more to extract and have smaller amounts of metal in ore

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35
Q

how is tungsten extracted and why

A

by hydrogen reduction because carbon makes it too brittle

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36
Q

what is the equation for the reaction between metal and oxygen
what is this reaction?

A

metal + oxygen —> metal oxides
oxidation because the metal gain oxygen

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37
Q

what is oxidation in terms of oxygen

A

gains oxidation in reaction

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38
Q

what is reduction in terms of oxygen

A

loss of oxygen in reaction

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39
Q

what is a reduction reaction

A

when a metal is separated from it oxide

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40
Q

how does potassium, sodium, lithium and calcium react with water

A

fizz, give of hydrogen, leaves alkaline solution of metal hydroxide

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41
Q

how does potassium, sodium, lithium react with dilute acid

A

explode

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42
Q

how does calcium react with dilute acid

A

fizz, give off hydrogen and form a salt

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43
Q

how does magnesium, aluminium, zinc and iron react with water

A

vey slow reaction

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44
Q

how does magnesium, aluminium, zinc and iron react with dilute acid

A

fizz, give off hydrogen, form a salt

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45
Q

how does tin and lead react with water

A

slight reaction with steam

46
Q

how does tin and lead react with dilute acid

A

react slowly with warm acid

47
Q

how does copper, silver and gold react with water

A

no reaction

48
Q

how does copper, silver and gold react with dilute acid

A

no reaction

49
Q

what does metal + oxygen produce

A

metal oxide

50
Q

what does metal and acid produce

A

a salt + hydrogen

51
Q

what does metal + water produce

A

metal hydroxide + hydrogen

52
Q

what is the speed of reaction indicated by

A

by the rate at which the bubbles of hydrogen are given off

53
Q

what is the reactivity series

A

a list of metals ranked in order of reactivity

54
Q

what happens when metal reacts with other substances

A

the metal atoms form positive ions

55
Q

what is the reactivity of a metal related to

A

its the tendency to form positive ions/ lose electrons

56
Q

what happens the higher up the reactivity series

A

the higher up the series the more easy it will form positive ions so more reactive

57
Q

what is often included in the reactivity series

A

carbon and hydrogen to give info about how metals react with them

58
Q

what is the list of the reactivity series

A

potassium
sodium
lithium
calcium
magnesium
CARBON
zinc
iron
HYDROGEN
copper

59
Q

how do you calculate the pH

A
  1. find the concentration of acid
  2. find the concentration of H+
  3. find pH
60
Q

ESQ calculate the pH of a solution of H2SO4 in which 0.0005 mol of H2 SO4 dissolved in 0.10dm3 of water

A

conc of acid= moles/volume= 0.0005/0.10= 5x10 -3 mol/dm3
conc of H += H2SO4 –> 2H+ + SO4 2-
5x10-3 –> 0.01 of H+
0.01= 1x10-2
pH=2

61
Q

how can soluble salts be made

A

from acids by reacting them with solid insoluble substances eg. metal, metal oxides, hydroxides or carbonates

62
Q

why is the solid added in excess to the acid

A

the solid is added to the acid in excess until it all reacts and the excess is filtered to produce a solution of salt

62
Q

what happens if ammonia is bubbled through water

A

it dissolves to produce an alkaline solution

63
Q

what is the method for making salts

A
  1. gently warm the dilute acid using a Bunsen burner, then turn it off
  2. add the insoluble base to the acid in excess to completely react all the acid-wait until it has fully reacted the excess will sink to bottom
    3.filter out the excess solid to get a salt solution
  3. to get pure solid crystals- gently heat the solution using a water bath/electric heater to evaporate some of the water
  4. stop heating and leave to cool
  5. crystals of the salt should form, they can be filtered out and dried
64
Q

what is produced when acid+ metal carbonate base react

A

a salt + water + co2

65
Q

what is produced when acid + ammonia solution reacts

A

salt+water

66
Q

what is produced when metal and oxygen reacts

A

metal oxide

67
Q

what is produced when metal and acid react

A

a salt + hydrogen

68
Q

what is produced when metal and water react

A

metal hydroxide + hydrogen

69
Q

what is the concentration

A

the concentration of an acid measures how much acid there is in a certain volume of water

70
Q

the — the amount of —- in a volume, the more —— the acid is

A

the larger the amount of acid in a volume, the more concentrated the acid is

71
Q

what will happen to the pH with increasing acid concentration

A

the pH will decrease

72
Q

you can have a —– but —- acid

A

you can have a strong but dilute acid

73
Q

what is the pH of an acid or alkali

A

a measure of the concentration of H+ ions in the solution

74
Q

ESQ the pH of a solution fell from pH 7 to pH 4. By what factor had the hydrogen ion concentration of the solution changed

A

difference= final pH-starting pH
4-7= -3
factor H+ ion changed=
10-(-3)= 103 or 1000

75
Q

what is a strong acid

A

ionises(dissociates) completely in solution

76
Q

what is a weak acid

A

only partially ionises in solution

77
Q

because a weak acid only partially ionises, what does this mean

A

it is a reversible reaction

78
Q

what are 3 examples of strong acids

A
  • hydrochloric acid
  • nitric acid
  • sulfuric acid
79
Q

what are 3 examples of weak acids

A
  • ethanoic acid
  • citric acid
  • carbonic acid
80
Q

what happens as the pH decreases by one unit

A

the H+ concentration of solution increase by a factor of 10
eg an acid of pH 4 has 10x conc of h+ ions of an acid of pH 5

81
Q

what is electrolysis

A

breaking down or splitting up using electricity

82
Q

what are electrolytes

A

liquids or solutions able to conduct electricity- molten or dissolved ionic compounds

83
Q

why is it important the electrolytes are molten or dissolved

A

so the ions are free to move and it can conduct electricity

84
Q

what is electrolysis used to extract

A

more reactive metals than aluminium

85
Q

what is the process of electrolysis

A
  • passing electric current through electrolytes cause the ions to move to the electrodes
  • positively charged ions move to the negative electrode(cathode)
  • negatively charged ions move to the positive electrode (anode)
  • ions are discharged at electrodes producing elements
86
Q

what is the rhyme to remember the electrodes

A

Postive
Anode
Negative
Cathode
ake

87
Q

what is an electrode

A

a solid that conducts electricity and is submerged in the electrolyte

88
Q

in copper chloride solution, which electrode does each one go to

A

copper- cu2+
chloride- cl-
copper-cathode
chloride- anode

89
Q

what happens to the positive ions in the electrolyte

A

the positive ions move to the cathode and gain electrons(reduced)

90
Q

what happens to the negative ions in the electrolyte

A

the negative ions moving to the anode lose electrons(oxidised)

91
Q

what should the properties of the electrodes be

A
  • high melting point
  • unreactive
92
Q

what are cations

A

positive ions

93
Q

what are anions

A

negative ions

94
Q

what happens to lead bromide during electrolysis

A
  • bromine loses 1 electron each to form a Br2 molecule
  • positive lead gains 2 electrons and becomes a lead atom- reduction
95
Q

why does the electrode(anode) need to be replaced regularly

A

they are made of carbon so react with the oxygen produced to form CO2

96
Q

when using aluminium what is produced at each electrode

A

cathode- aluminium
anode- produces oxygen

97
Q

what is the problem with electrolysis

A

very expensive and requires lots of energy

98
Q

how is aluminium manufactured

A

by the electrolysis of a molten mixture of aluminium oxide and cyolite

99
Q

why is aluminium a mixture

A

aluminium oxide has a very high melting point- its mixed with cryolite to lower the melting point- uses less energy, so cheaper and less polluting

100
Q

how do you predict with ions will discharge at the cathode

A
  1. metal or hydrogen
  2. if the metal is more reactive than hydrogen it will remain in solution and hydrogen gas will be produced
  3. if metal is less reactive, a solid pure metal will be produced
101
Q

how do you predict what ions will discharge at the anode

A
  1. halides(cl-,Br-,L-) molecules chlorine ,bromine or iodine formed
  2. hydroxide (OH-) and oxygen produced
  3. other negative ions
102
Q

what is important when writing half equations

A

same number of atoms/ions on either side
- charge on either side is equal

103
Q

what does a half equation show

A

show reactions at the electrodes

104
Q

at the cathode, hydrogen produced unless metal is more reactive
at the anode, oxygen is produced unless halide ions are there
- why does this happen

A

in the solution, water molecules break down and produce hydrogen/hydroxide ions that are discharged

105
Q

what is present in every aqueous solutions

A

OH- and H+

106
Q

when copper sulphate is electrolysed what is produced at each electrode

A

anode- no halide ions so oxygen + water are produced
cathode- copper is less reactive than hydrogen so copper is produced

107
Q

when sodium chloride solution is electrolysed what is produced at each electrode

A

anode- chloride ions are present so chlorine gas produced
cathode- sodium is more reactive than H+ so hydrogen gas is formed

108
Q

what is the test for hydrogen

A

produces ‘squeaking pop’ from lit splint

109
Q

what is the test for oxygen

A

relights a glowing splint

110
Q

what is the test for chlorine

A

turns damp blue litmus paper red, then bleaches it

Paper1- Chemistry (4 decks)

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