Chemical Changes Flashcards
(119 cards)
1
Q
What is the reactivity series
A
An arrangement of metals in order of their reactivity
2
Q
The reactivity series
A
Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Hydrogen
Copper
Silver
Gold
Platinum
3
Q
Reactivity series higher than carbon
A
Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
4
Q
Reactivity series higher than hydrogen and lower than carbon
A
Zing
Iron
Tin
Lead
5
Q
Reactivity series from lower than hydrogen
A
Copper
Sliver
Gold
Platinum
6
Q
What happens when metals more reactive than carbon react with oxygen
A
They burn to form oxide
7
Q
What happens when metals in the middle of the reactivity series (below carbon but above hydrogen) react with oxygen
A
They react with oxygen and form oxide when heated and can burn if the metal is powdered
8
Q
What happens when copper (low reactivity metal reacts with oxygen
A
It reacts with oxygen when heated forming a layer of copper oxide on the surface of the copper but does not burn
9
Q
What happens when metals less reactive than hydrogen (excluding copper) react with oxygen
A
There is no reaction
10
Q
Reaction for metal + oxygen if metals react with oxygen
A
Metal + oxygen -> metal oxide
11
Q
What is an oxidation reaction in terms of oxygen
A
When a substance gains oxygen
12
Q
What is a reduction reaction when in terms of oxygen
A
A reaction where a substance loses oxygen
13
Q
Reaction for metal + water for metals which react with cold water
A
Metal + water -> metal hydroxide + hydrogen
14
Q
What happens with metals more reactive than carbon when reacted with water
A
They react and give off H2 (gas)
Other than aluminium which does not react
15
Q
What happens with metals less reactive than carbon (and aluminium) when reacted with water
A
No reaction
16
Q
Observations when magnesium reacts with cold water
A
Very slow reaction
17
Q
Observations when calcium reacts with cold water
A
Fizzes, white solid forms
18
Q
Observations when lithium reacts with cold water
A
Fizzes, floats and moves on the surface of the water
19
Q
Observations when sodium reacts with cold water
A
Fizzes, melts, floats and moves on the surface of the water (sometimes there is a yellow-orange flame
20
Q
Observations when potassium reacts with cold water
A
Fizzes, melts, floats and moves on the surface of the water, lilac flame.
21
Q
What happens when metals less reactive than hydrogen react with dilute acids
A
No reaction
22
Q
What happens and observations with metals in the middle of the reactivity series (below carbon but above hydrogen) react with dilute acids
A
Reacts slowly and gives off H2 and fizzes slowly
23
Q
What happens and observations when metals more reactive than carbon but less reactive than lithium react with dilute acids
A
It reacts and gives off H2 and fizzes
24
Q
Definition of dilute
A
Less concentrated
25
Example of acids and what salts they make
Hydrochloric acid makes chloride salts
Sulfuric acid makes sulfate salts
Nitric acid makes nitrate salts
26
Equation for metal + acid
Dilute acids
Metal + acid -> metal salt + hydrogen
27
Why can’t metals less reactive than hydrogen react with acids
Because they can’t give off H2 (hydrogen)
28
Why are high reactivity metals reaction with acids explosive
Due to the hydrogen formed igniting
29
What happens when lithium sodium and potassium react with dilute acids and observations
They react violently and give off H2 and is explosive
30
What is a displacement reaction
Where a more reactive element takes the place of a less reactive element in a compound
31
What happens to metal atoms when they react
The lose electrons to form positive ions
32
What makes a metal reactive
The greater the tendency of a metal/easier it is for them to lose all their outer shell electrons to form ions
33
Example of real life displacement reaction used
Aluminium + iron oxide -> aluminium oxide + iron
A mixture of aluminium and iron oxide is placed over the gap between railway lines and the reaction starter. The reaction gee very hot and produced molten iron which flows into a mould, cools and solidifies to weld the lines together
34
Example of displacement reaction in solution
Copper + silver nitrate -> copper nitrate + silver
Silver forms on the copper wire as silver is displaced from the sliver nitrate solution and copper nitrate is blue so the solumetal ion turns blue when copper nitrate is formed
35
Oxidation in terms in electrons
A reaction in which a substances loses electricians
36
Reduction in terms of electrons
Reaction in which a substance gains electrons
37
What is the only reaction that can be defined as oxidation in terms of oxygen
Metals reacting with oxygen
38
When speaking about equations involving displacement are the ions found in the element or in the compound
Always in the compound
39
Example of redox reaction
Aluminium and iron displacement
40
Redox reaction meaning
A reaction where both reduction and oxidation take place
41
How is silver, gold and platinum extracted
They are metals found naturally on Earth as elements
42
What are most metals on earth found as
Compounds
43
Definition of pre
A rock from which a metal can be extracted for profit
44
What are most of the compounds which metals are extracted from
Metal oxides
45
How are metals less reactive than carbon but not found naturally as elements extracted
Their metal oxides are heated with carbon which displaces the metal from the metal oxide as the carbon is more reactive. The metal oxide is reduced in this reaction
46
How are metals more reactive than carbon extracted by
Electrolysis
47
What do acids produce in water
H+ ions
48
What do alkalis produce in water
OH- ions
49
What does aqueous mean
Dissolved in water
50
Definition of acid
Solution with a pH less than 7 and produces H+ ions in water
51
Definition of alkali
Solution with a pH more than 7 and produces OH- ions in water (remember the - and + in H+ and OH- ions are found like where a square or cubed symbol would be found)
52
What do all acids contain
Hydrogen
53
What do all alkalis contain
Hydroxide
54
What does the pH scale range from
0-14
55
What is neutral pH
7
56
Does the scale of pH go any further than 0-14 and example
Yes as in some laboratories solutions of acids have a pH less than 0 such as -0.3
57
How is universal indicator used
A few drops of the indicator added to the solution and colour is compared to a colour chart to give the approximate pH of the solution
58
What colour is neutral solution when in universal indicator
Green
59
What colour is 5 pH when in universal indicator
Yellow
60
What colour from 4-0 on pH scale is solutions when in universal indicator
From orange to dark red
61
How does the colour of pH go from 8-14 in colour chart when in universal indicator
From blue to purple to brownish
62
Why is pH probe better for testing
Because colour can be subjective to a degree and pH probe is more accurate showing the correct pH and often to 1 or 2 decimal places
63
What is the concentration of ions in a neutral solution
The concentration of H+ ions equals the concentration of OH- ions
64
What is the correlation between pH of one unit and concentration of hydrogen ions
When the pH decreases by one unit, the concentration of hydrogen ions increases by a factor of 10
65
Definition of strong acid
Acid in which all the molecules break into ions in water
66
Definition of weak acid
Acid in which only a small fraction of the molecules break into ions in water
67
Examples of strong acids and why
Hydrochloric acid
Sulfuric acid
Nitric acid
Because their molecules are completely ionised in water meaning all their molecules break into ions in water
68
What type of solutions does testing if something is acid by putting it into water form
Aqueous solutions
69
Examples of weak acids where they are found and why they are weak
Ethanoic acid in vinegar, citric acid in citrus fruits and carbonic acid in fizzy drinks.
Because the molecules are only partially ionised in water meaning that only a small fraction of the molecules break into ions when added to water
70
Dilute definition
A solution in which there is a small amount of solute dissolved
71
Concentrated definition
A solution in which there is a lot of solute dissolved
72
Reaction of acids with metals
Metal + acid -> metal salt + hydrogen
73
Example of redox reaction overall
When a metal reacts with an acid to form metal salt plus hydrogen
74
Metal hydroxide + acid
Metal hydroxide + acid -> metal salt + water
75
Examples of neutralisation reaction and why
Metal hydroxide + acid -> metal salt + water
Metal oxide + acid -> metal salt + water
Metal carbonate + acid -> metal salt + water + carbon dioxide
Because the reaction uses up some or all of the H+ ions from an acid
76
Are metal hydroxides alkalis
Metal hydroxides which dissolve in water and release OH- ions into the water are however those that are insoluble in water are not alkalies however do still react with acids to produce a salt and water
77
Metal oxide + acid
Metal oxide + acid -> metal salt + water
78
What is special about the reaction of acids with metal oxides
Most metal oxides are insoluble in water and the reactions usually need to be heated
79
Metal carbonate + acid
Metal carbonate + acid -> metal salt + water + carbon dioxide
80
Observations in reaction or acid with metal carbonates
The reaction fizzes as carbon dioxide is produced.
These reactions usually take place readily
81
Uses of salts
Many medicines are salts
Fertilisers are salts
Toothpaste contains salts
Many food additives are salts
82
What are salts
Substances made when acids react with metals, metal hydroxides, metal oxides and metal carbonates
83
When is salt made in the reactions
When the metal ion combines with the ion left over from the acid when the H+ ions react
84
Process of making soluble salts
React the acid with an insoluble substance to produce the desired salt. Add this substance until it no longer reacts and this reaction may need to be heated. Filter off the left over metal/metal oxide/metal hydroxide/metal carbonate as it was added in excess for reaction. Heat the solution to evaporate until crystals start to form. Leave the solution to cool down so more crystals will form. Filter off the crystals of the salt. Allow the crystals to dry.
85
What is the benefit of reacting acids with an insoluble substance rather than a soluble substance when making soluble salts
As it is insoluble you can add an excess of that substance to ensure that all the acid is used up and the excess can then be filtered off. In this way there is no left left acid or the substance it reacts with mixed in with the salt that is formed
86
Salt that only forms anhydrous crystals (crystals containing no water) example
Sodium chloride
87
What are hydrated crystals salts and example
Crystals of salts within the crystals substance. Blue crystals of Copper (II) sulfate.
88
When is it not possible to form hydrated crystals
When an aqueous solution of a soluble salt is heated to evaporate all the water
89
What is electrolysis
The decomposition of ionic compounds using electricity
90
Can solid ionic compound conduct electricity and whyo
They cannot because the ions cannot move around
91
Why are ionic compounds dissolved or melted for electrolysis
Because when they are solids the ions are not free to move but as liquids it solutions the ions are free to move and conduct electricity
92
What are electrolytes
The liquids or solutions made when ionic compounds are melted or dissolved - a liquid that conducts electricity
93
What does discharge mean
Gain or lose electrons to become electrically neutral
94
What happens in electrolysis of molten or dissolved ionic compounds
If two electrodes connected to a supply of electricity are put into the electrolyte, the negative ions are attracted to the positive electrode (anode) and the positive ions are aggravated to the negative electrode (cathode) because opposite charges attract each other. When the ions reach the electrodes they are discharged to become neutral and the electrons then move around the circuit through wire to add electrons to the positive ion.
95
What happens at the positive electrode (anode)
Oxidation (loss of electrons)
96
What happens at the negative electrode (cathode)
Reduction (gain of electrons)
97
Where are non metals and metals produced in electrolysis of molten ionic compounds
Metal at the cathode and non-metal at the anode
98
What are binary ionic compounds
Ones made from one metal combined with one non-metal
99
For ionic compounds of number and charges what method to do for formula or something
Circle and down across
100
Why can some metal compounds in ores not be extracted by heating with carbon for a displacement reaction
Because:
Some metals are more reactive than carbon and/or
Some metals would react with carbon in the process
101
Why are metals produced by electrolysis expensive
Because of:
The high cost of thermal energy to melt the metal compounds
And
The high cost of the electricity for the process
102
What is the second-most commonly used metal after iron/steel
Aluminium
103
What is the main ore for aluminium called and its melting point
Bauxite which contains aluminium oxide and it has a very high melting point of 2072°C.
104
Thene
105
What is the name of the substance aluminium oxide is mixed with for electrolysis and why
Either cryolite which lowers the melting point to about 950°C and so the cost of thermal energy to melt this mixture is lower
106
What are the electrodes for the electrolysis of aluminium made from
Graphite, a form of carbon.
107
What is produced at the negative electrode of the electrolysis of aluminium oxide
Aluminium metal is formed but as it is so hot this is produced as a liquid and is run off at the bottom.
108
What happens at the positive electrode of the electrolysis of aluminium oxide
Oxide ions (02-) are attracted to the positive electrode where they lose electrons and form oxygen. This oxygen reacts with the carbon anode and so the anode burns to produce carbon dioxide
109
Why does the anode (positive electrode) need to be replaced regularly in the electrolysis of aluminium oxide
Because when oxygen is produced at the anode it reacts with the carbon anode and so the anode burns to produce carbon dioxide
110
Why are some of the products of aqueous ionic compounds different to those of molten ionic compounds in electrolysis
Because in water a small fraction of the molecules break down into hydrogen ions and hydroxide ions which can be discharged instead of the ions in the ionic compound. More water molecules can break down if these ions are used up. At each electrode there are two ions that could discharge ine from the ionic compound and one from the water. The one that is easier to discharge is discharged.
111
What are inert electrodes
Electrodes that allow electrolysis to take place but do not react themselves
112
What is the most common inert electrode
Graphite electrodes
113
What happens at the positive electrode of electrolysis of aqueous solutions of ionic compounds when inert electrodes are used
Negative ions discharged.
Oxygen is produced from the discharge of hydroxide ions from the water (unless the ionic compound contains halide ions when these are discharged producing a halogen)
114
What happens at the negative electrode of electrolysis of aqueous solutions of ionic compounds when inert electrodes are used
Positive ions discharged.
Hydrogen is produced from the discharge of hydrogen ions from the water, unless the ionic compound contains metal ions from a metal that is less reactive than hydrogen when the metal ions are discharged producing the metal
115
How to test for chlorine
It bleaches damp litmus paper turning it white
116
How to test for hydrogen
It makes a “squeaky pop” sound with a lighted splint
117
How to test for oxygen
It will relight a glowing splint
118
Negative electrode half equation with aqueous solution it not more revive than hydrogen
2H+ + 2e -> H2
119
Positive electrode half equation of aqueous solution if halide isn’t present
4OH- - 4e- -> O2 + 2H20
