Chemical Changes & Metals Flashcards
(99 cards)
1
Q
How reactivity determined for metals?
A
Reactivity is determined how easily they lose electrons
2
Q
The higher up a metal is in the reactivity series means…
A
The more easily it’ll form positive ions (and the more easily it’ll react with water or acid)
3
Q
What happens when metals react with water or an acid?
A
They lose electrons and form positive ions
4
Q
Metals below hydrogen in the reactivity series will…
A
Not react with acid
5
Q
Metals above hydrogen in the reactivity series will…
A
React with acids
6
Q
How can metals that are less reactive than carbon be extracted from their ores?
A
By reduction with carbon
7
Q
How can metals that are more reactive than carbon be extracted from their ores?
A
Using electrolysis
8
Q
Recite the reactivity series
A
Potassium
Sodium
Lithium
Calcium
Magnesium
Carbon
Zinc
Iron
Hydrogen
Copper
9
Q
Acid + Metal →
A
Salt + Hydrogen
10
Q
Metal + Water →
A
Metal Hydroxide + Hydrogen
11
Q
How will very reactive metals (potassium, sodium, lithium, calcium) react with acid?
A
They’ll react explosively
12
Q
How will less reactive metals (magnesium, zinc, iron) react with acid?
A
Less violently (than very reactive materials)
13
Q
Will copper react with cold, dilute acid?
A
No
14
Q
The more reactive metal is, the ____ the reaction will go
A
faster
15
Q
What is the speed of reaction (metal + acid) indicated by?
A
Rate of the bubbles of hydrogen given off
16
Q
What metals will react with water?
A
Reactive metals like potassium, sodium, lithium & calcium
17
Q
What metals will not react with water?
A
Less reactive metals like zinc, iron & copper
18
Q
How does magnesium react with cold, dilute acid?
A
Vigorously and produces a lot of bubbles
19
Q
How does zinc and iron react with cold, dilute acid?
A
Fairly slowly (speed up if heated)
20
Q
How can smelting be used to obtain copper?
A
Heat copper ores in a furnace to extract high concentrations of copper
21
Q
What is an advantage of smelting?
A
Get large amounts of copper
22
Q
What is a disadvantage of smelting?
A
Time consuming
23
Q
How can bioleaching be used to obtain metal?
A
Uses bacteria to produce leachate solutions that contain metal compounds
24
Q
What is an advantage of bioleaching?
A
- More simpler/cheaper to operate/maintain
- Environmentally friendly
25
What is a disadvantage of bioleaching?
Very slow (compare to like smelting)
26
How can phytomining be used to obtain copper?
1. Crops are planted on soil that contains very small amounts of copper
2. The plants absorb the copper through their roots
3. Plants are burnt to ashes to extract copper
27
What is an advantage of phytomining?
Easier to use plants than mining - cheaper
28
What is a disadvantage of phytomining?
Metal is poor quality - many impurities
29
How can electrolysis be used to obtain copper?
Electricity is used to break down copper compounds into copper elements
30
What is an advantage of electrolysis?
Get pure copper atoms
31
What is a disadvantage of electrolysis?
1. Takes a lot of electricity
2. Expensive
32
What is an alloy?
Mixture of at least two elements, where at least one of these is a metal
33
How are the atoms arranged in a metal?
There are layers of metal atoms which can move easily
34
How are the atoms arranged in an alloy?
Layers of atoms in alloys are disrupted so they don't move easily
35
How are alloys made?
By adding another element to a metal = disrupts structure of metal, making alloys harder than pure metals
36
Acid + Metal Carbonate →
Salt + Water + Carbon Dioxide
37
What is thermal decomposition?
When heat is used to break substances down
38
Do all carbonates of metals in Group 1 decompose at temperatures reached by a Bunsen burner?
No
39
Why aren't most metals found in earth in their pure forms?
They're fairly reactive so they're found as compounds
40
What is an ore?
A type of rock that contains metal compounds
41
What are native metals?
Metals are so unreactive that they're found in their elemental form (silver, gold)
42
What is oxidation?
Gain of Oxygen
43
What is reduction?
Loss of Oxygen
44
Why can only metals below carbon in the reactivity series be extracted by reduction using carbon?
Because carbon can only take oxygen away from metals which are less reactive than it
45
What does OIL RIG stand for?
Oxidation is Loss, Reduction is Gain
46
What is REDOX?
REDuction and OXidation happen at the same time
47
Write the 2 half ionic equations & the ionic equation for when chorine reacts with potassium bromide solution (halogens)
48
Write the 2 half ionic equations & the ionic equation for when iron reacts with dilute sulfuric acid
49
What is a displacement reaction?
When a more reactive metal replaces a less reactive metal from its compound
50
In a displacement reaction, what happens to the metal ions?
Gain electrons and are reduced
51
In a displacement reaction, what happens to the metal atoms?
Loses electrons and is oxidised
52
What is are metal displacement reactions essentially?
Redox reactions
53
What is electrolysis?
Passing electric current through molten/dissolved ionic substances to break them down into elements
54
What is an electrolyte?
Molten or dissolved ionic compound (so ions are free)
55
Explain the electrolysis process
1. Electric current passes through electrolyte
2. Ions move towards electrodes - where they react = compound decomposes
1. Negative ions in electrolyte will move towards anode (+ve electrode) & lose electrons (they’re oxidised) = form uncharged element
2. Positive ions in electrolyte will move towards cathode (-ve electrode) & gain electrons (they’re reduced) = form uncharged element
3. This creates flow of charge through electrolyte as ions travel to electrodes
56
Why can't an ionic solid be electrolysed?
Ions in fixed positions - can’t move
57
Why can we electrolyse molten ionic compounds?
Electrolysed bc ions can move freely + conduct electricity
58
What type of material are electrodes made from and why?
From inert material = don’t react with electrolyte
59
Molten ionic compounds are always...
broken up into their elements
60
Explain how aluminium is extracted from its ore
1. Aluminium is extracted from ore bauxite by electrolysis
2. Aluminium oxide = very high melting temperature ∴ mixed with cryolite to lower melting point
3. Molten mixture contains free ions - conduct electricity
4. Positive Al3+ ions attracted to negative electrode, where they pick up 3 electrons & turn into neutral aluminium atoms → sink to bottom of electrolysis tank
5. Negative O2- ions are attracted to positive electrode, where they each lose two electrons → neutral oxygen atoms then combine to form O2 molecules
61
Why does the anode need to regularly replaced when extracting aluminium from its ore?
Made from carbon = regularly reacts with oxygen to produce carbon dioxide
62
What is the ionic half equation at the negative electrode? (aluminium extraction)
Al3+ + 3e- → Al
63
What is the ionic half equation at the positive electrode? (aluminium extraction)
2O2- → O2 + 4e-
64
What is word equation for aluminium extraction?
Aluminum oxide → aluminium + oxygen
65
What is symbol equation for aluminium extraction?
2Al2O3(l) → 4Al(l) + 3O2(g)
66
Name 3 energy costs of extracting aluminium
1. Bauxite purification
2. Aluminum ore has to be minded
3. Extracting aluminium
4. Carbon anodes are replaced regularly
67
Name 3 environmental costs of extracting aluminium
1. Fuels used to keep aluminium hot
2. Make CO2 because carbon is used for anode
3. Electricity is used
68
What is brine?
Solution of sodium chloride & water
69
What does the electrolysis of brine produce?
Chorine, hydrogen and sodium hydroxide
70
Name 3 uses of chlorine
1. Disinfectant and purifier
2. Manufacture of hydrochloric acid
3. Making plastics
71
Name 2 uses of hydrogen
1. Manufacture of hydrochloric acid
2. Potential as a pollution-free fuel
72
Name 4 uses of sodium hydroxide
1. Removing pollutants from water
2. Processing food products
3. Manufacture of paper
4. Soap production
73
Where is the object being electroplated made?
At the cathode (in an electrolysis cell)
74
Where is the plating metal made (electroplating)?
At the anode
75
When electroplating, what does the electrolyte contain?
Contains ions of plating metal
76
When electroplating, at the anode (made of zinc), what happens?
1. Zinc atoms in electrode are oxidised
2. Lose 2 electrons each & form zinc ions
3. Which leave anode and go into solution
77
When electroplating, at the anode (made of zinc), what is the half ionic equation?
Zn(s) → Zn2+(aq) + 2e-
78
When electroplating, at the cathode (where copper foil is to be plated), what happens?
1. Zinc ions from solution are reduced
2. Gain 2 electrons & form zinc atoms
3. Which are deposited on copper cathode
79
When electroplating, at the cathode (where copper foil is to be plated), what is the half ionic equation?
Zn2+ (aq) + 2e- → Zn(s)
80
Why are objects electroplated? (name 3 reasons)
1. To improve their appearance
2. To protect their surface
3. To use smaller amounts of precious material
81
Electrolysis: What ions are there in aqueous solutions?
1. Hydrogen ions (H+) and hydroxide ions (OH-) from water
2. Ions from ionic compound
82
Electrolysis of Aqueous Solutions: Which ions are discharged at electrodes when solution is electrolysed depends on...
relative reactivity of all ion in solution
83
Electrolysis of Aqueous Solutions: At the cathode, if H+ ions & metal ions are present...
Hydrogen gas will be produced if metal ions form elemental metal that's more reactive than hydrogen
84
Electrolysis of Aqueous Solutions: At the cathode, if metal ions form element metal that's less reactive than hydrogen...
Solid layer of pure metal will be produced instead which coats cathode
85
Electrolysis of Aqueous Solutions: At the anode, if OH- and halide ions are present...
Molecules of chlorine, bromine or iodine formed
86
Electrolysis of Aqueous Solutions: At the anode, if no halide ions are present...
OH- ions discharged and oxygen formed
87
Electrolysis of Copper Sulfate Solution: Why does copper coat the cathode?
Because copper is less reactive than hydrogen so at the cathode it's produced
88
Electrolysis of Copper Sulfate Solution: Why are oxygen and water produced at the anode?
No halide ions present
89
Electrolysis of Copper Sulfate Solution: What is the half ionic equation at the cathode?
Cu2+ + 2e- → Cu
90
Electrolysis of Copper Sulfate Solution: What is the half ionic equation at the anode?
4OH- → O2 + 2H2O + 4e-
91
Electrolysis of Sodium Chloride Solution: Why is hydrogen gas produced at the cathode?
Sodium metal is more reactive than hydrogen
92
Electrolysis of Sodium Chloride Solution: Why is chlorine gas produced at the anode?
Chloride ions are present in the solution
93
Electrolysis of Sodium Chloride Solution: What is the half ionic equation at the cathode?
2H+ + 2e- → H2
94
Electrolysis of Sodium Chloride Solution: What is the half ionic equation at the anode?
2Cl- → Cl2 + 2e-
95
What does cryolite do to aluminium oxide?
Lowers its melting point?
96
How does cryolite lower aluminium oxide's melting point?
Weakens attractions in aluminium oxide
97
Explain how carbon dioxide is produced at the anode during the electrolysis of aluminium oxide (4 marks)
* Oxide/O2- ions attracted to anode
* Oxygen gas is produced
* Anodes made from carbon
* Carbon reacts with oxygen to produce CO2
98
What does (aq) - aqueous mean?
Dissolved in water
99
Electrolysis of Aqueous Solutions: Why do you get H+ and OH- ions?
Bc water molecules ionise (spilt), forming them
