3 - Elements from the Sea (ES) Flashcards
1
Q
Define oxidation
A
-gain of oxygen
-loss of electrons
2
Q
Define reduction
A
-loss of oxygen
-gain of electrons
3
Q
Define redox reaction
A
Where one element is oxidised and one is reduced
4
Q
Define precipitate
A
Insoluble solid produced by the reaction of two solutions
5
Q
Define ionic equation
A
Equation with no spectator ions
6
Q
State of chlorine at room temperature
A
Gas
7
Q
State of bromine at room temperature
A
Liquid
8
Q
State of iodine at room temperature
A
Solid
9
Q
Colour of chlorine at room temperature
A
Pale green
10
Q
Colour of bromine at room temperature
A
Brown
11
Q
Colour of iodine at room temperature
A
Grey
12
Q
Describe the reactivity of the halogens
A
-gain one electron
-smaller = gain electrons more readily (fluorine most reactive)
13
Q
Colour of chlorine in cyclohexane
A
Colourless
14
Q
Colour of bromine in cyclohexane
A
Pale orange/yellow
15
Q
Colour of iodine in cyclohexane
A
Purple
16
Q
Effect of adding dilute ammonia to AgCl
A
Precipitate dissolves
17
Q
Effect of adding dilute ammonia to AgBr
A
No change
18
Q
Effect of adding dilute ammonia to AgI
A
No change
19
Q
Effect of adding concentrated ammonia to AgCl
A
Precipitate dissolves
20
Q
Effect of adding concentrated ammonia to AgBr
A
Precipitate dissolves
21
Q
Effect of adding concentrated ammonia to AgI
A
No change
22
Q
Define oxidation number/state
A
Measure of the number of electrons an atom uses to bond with atoms of another element
23
Q
What happens to the oxidation number during oxidation?
A
Number increases
24
Q
What happens to the oxidation number during reduction?
A
Number decreases
25
Oxidation numbers of elements
0
26
Oxidation numbers of simple ions
Charge of ion
27
Oxidation numbers of oxygen in compounds
-2
28
Oxidation numbers of hydrogen in compounds
+1
29
Sum of oxidation numbers in compounds
0
30
Sum of oxidation numbers in complex ions
Ion charge
31
Oxidation numbers of oxygen in peroxides
-1
32
Oxidation numbers of hydrogen in metal hydrides
-1
33
Benefits of oxidation numbers
Half equations not necessary
34
Define disproportionation reaction
Reaction where an element is simultaneously reduced and oxidised
35
Define reducing agent
Chemical that reduces another by providing electrons and gets oxidised in the process
36
Best halogen reducing agent
Iodide ions, outer shell electron is lost more readily due to weaker attraction
37
Define oxidising agent
Chemical that oxidises another by removing electrons and gets reduced in the process
38
Best halogen oxidising agent
Fluorine, electrons are gained more readily due to greater attraction
39
Uses and benefits of chlorine
-killing bateria in water
-making bleach
-production of plastics (PVC)
40
Transportation and risks of chlorine
-toxic
-needs to be transported under pressure as a liquid
-sometimes needs to be stored for a long time
41
What is chlorine stored as?
Sodium hypochlorite (NaClO)
42
Why is chlorine stored in a compound?
-less toxic
-does not require storage under pressure
43
Define reversible reactions
Can go forwards and backwards and only occurs in a closed system
44
Define dynamic equilibrium
Rate of forward reaction = rate of backward reaction
45
What is Kc for A+B ⇌ C+D?
[C][D]/[A][B]
46
What is Kc for 2A+B ⇌ 2C+D?
[C]^2[D]/[A]^2[B]
47
What do the square brackets in Kc calculation represent?
Concentration
48
Factors affecting Kc
-temperature
-pressure
-concentration
-catalyst
49
How does temperature affect Kc?
-Kc is only valid at one temperature
-changing temperature will change equilibrium concentrations
50
In an exothermic reaction, how would increasing the temperature affect the reaction and Kc?
-equilibrium shifts in the endothermic direction
-increases reactant concentration
-Kc decreases
51
In an exothermic reaction, how would decreasing the temperature affect the reaction and Kc?
-equilibrium shifts in the exothermic direction
-increases product concentration
-Kc increases
52
How does pressure affect Kc?
No effect
53
How does concentration affect Kc?
No effect
54
How does a catalyst affect Kc?
No effect
55
How does a temperature increase shift equilibria?
-increases rate of reaction, more KE
-shifts in endothermic direction
56
How does a pressure increase shift equilibria?
-increases rate of reaction, particles in a smaller space
-increases yield in the direction of fewest molecules (only for gases)
57
How does an increase in the concentration of reactants shift equilibria?
-increases rate of reaction, more particles
-shifts to the right
58
How does a catalyst shift equilibria?
-lowers activation energy
-no affect on yield
59
Define electrolysis
Breaking down of a substance with electricity
60
What is a half equation?
Equation that shows the movement of electrons and what happens at each electrode
61
What product forms at the cathode in an aqueous solution?
-metal less reactive than hydrogen = metal forms
-metal more reactive than hydrogen = hydrogen forms
62
What product forms at the anode in an aqueous solution?
-no halide ion = oxygen formed
-concentrated solution and halide ion = halogen formed
-dilute solution and halide ion = oxygen formed
63
What is the anode made out of in the electrolysis of the purification of copper?
Impure copper
64
What is the cathode made out of in the electrolysis of the purification of copper?
Pure copper
65
What happens at the anode in the electrolysis of the purification of copper?
-anode wears away (gets lighter)
-electrons lost
66
What happens at the cathode in the electrolysis of the purification of copper?
-copper ‘plates’ cathode (gets heavier)
-electrons gained
67
Define brine
High concentration solution of salts
68
Half equation at the cathode for the electrolysis of sodium chloride
2H+ + 2e- —> H2
69
Half equation at the anode for the electrolysis of sodium chloride
2Cl- —> Cl2 + 2e-
70
Ionic equation of the production of water and oxygen in dilute sodium chloride
4OH- —>
2H2O + O2 + 4e-
71
How is bromine extracted from brine?
With a more reactive halogen
72
After bromine is extracted, what state is it in?
Liquid
73
How is iodine extracted from brine?
With a more reactive halogen
74
After iodine is extracted, what state is it in?
Grey solid
75
Define atom economy
How efficient a reaction is
76
Equation for atom economy
Mr of desired product/Mr of all products x 100
77
Importance of high atom economy
-produces less waste
-materials used more sustainably
-less by-products
78
Define hydrogen halide
Molecule that has a hydrogen and halide ion
79
How can a hydrogen halide be formed?
Added concentrated phosphoric acid
80
Equation for formation of HCl from NaCl
NaCl + H3PO4 —> HCl + NaH2PO4
81
Ionic equation for the formation of HCl from NaCl
Cl- + H3PO4 —> HCl + H2PO4-
82
Are halide ions oxidising or reducing agents?
Reducing agents
83
Which halogen is the strongest reducing agents?
Iodide - large atomic radius, causing more shielding
84
What is the equation for the reaction of sodium chloride with sulphuric acid?
NaCl + H2SO4 —> NaHSO4 + HCl
85
Is sulphuric acid an oxidising or reducing agent
Oxidising agent
86
What is produced in the formation of HCl?
White misty fumes
87
Why are there no further equations for NaCl and H2SO4?
Chloride ions do not reduce the sulphur any further as it is not a strong enough reducing agent
88
First equation for the reaction of sodium bromide and sulphuric acid
NaBr + H2SO4 —> NaHSO4 + HBr
89
Second equation for the reaction of sodium bromide and sulphuric acid
H2SO4 + 2HBr —> Br2 + SO2 + 2H2O
90
What is produced in the formation of bromine from NaBr?
Orange vapour of Br2 produced
91
First equation for the reaction of sodium iodide and sulphuric acid
NaI + H2SO4 —> NaHSO4 + HI
92
Second equation for the reaction of sodium iodide and sulphuric acid
H2SO4 + 2HI —> I2 + SO2 + 2H2O
93
Third equation for the reaction of sodium iodide and sulphuric acid
H2SO4 + 6HI —> 3I2 + S + 4H2O
94
Fourth equation for the reaction of sodium iodide and sulphuric acid
H2SO4 + 8HI —> 4I2 + H2S + 4H2O
95
What is the physical property formed in the third reaction for sodium iodide and sulphuric acid
Yellow solid of S produced
96
What physical property is formed in the second reaction for sodium iodide and sulphuric acid
Purple vapour of I2 produced
97
What physical property is formed in the fourth reaction for sodium iodide and sulphuric acid
Rotten egg smell from H2S
98
Ionic equation of dissociation of hydrogen halides
HCl(g) —> H+(aq) + Cl-(aq)
99
Equation for the dissociation of hydrogen halides and water
HCl(g) + H2O —> H3O+(aq) + Cl-(aq)
100
Trend of thermal stability of hydrogen halides
Decreases going down group 7, larger ions
