* Topic 4 - Inorganic chemistry and the periodic table Flashcards
1
Q
What happens to atomic radius down the groups?
A
Increases
2
Q
What happens to melting point of group 2 metals down the group and explain why
A
The melting point decreases. This is because metallic bonding weakens as atomic size increases. The distance between positive ions and delocalised electrons increases. Therefore, the electrostatic attractive forces between the positive ions and the delocalised electrons weaken.
3
Q
How does 1st ionisation energies of group 2 metals differ down the group?
A
- 1st ionisation energy decreases down the group
- Successively further from the nucleus (more electron shells)
- Outer shells become more shielded from the attraction of the nucleus by the repulsive force of inner shell electrons
- Overweighs the increase in nuclear charge
4
Q
What is the trend in reactivity of group 2 metals down the group?
A
Reactivity increases down the group
5
Q
Explain the trend in reactivity of group 2 metals down the group?
A
- Reactivity increases
- Atomic radii increases
- More shielding
- Nuclear attraction decreases
- Therefore easier to remove outer electrons so cations form more easily
6
Q
Give the equation and observation of the reaction of magnesium burning in oxygen (and the product)
A
- 2Mg + O2 -> 2MgO
- Mg burns with a bright white flame
- MgO is a white solid with a high melting point due to its ionic bonding
7
Q
How is the layer of magnesium oxide cleaned off a magnesium ribbon before a reaction with acid and why is it done?
A
- It is cleaned off with emery paper
- It is done as an uncleaned Mg ribbon would give a false result because both the Mg and MgO would react but at different rates:
- Mg + 2HCl -> MgCl2 + H2
- MgO + 2HCl -> MgCl2 + H2O
8
Q
How is the layer of magnesium oxide cleaned off a magnesium ribbon before a reaction with acid and why is it done?
A
- It is cleaned off with emery paper
- It is done as an uncleaned Mg ribbon would give a false result because both the Mg and MgO would react but at different rates:
- Mg + 2HCl -> MgCl2 + H2
- MgO + 2HCl -> MgCl2 + H2O
9
Q
Describe the reaction of Magnesium with water
A
- Reacts in steam to produce magnesium oxide + hydrogen
- Mg burns with a bright white flame
- Mg(s) + H2O(g) -> MgO(s) + H2(g)
10
Q
How does the reaction of magnesium with steam differ from that of magnesium with warm water?
A
- Steam produces MgO vs warm water produces Mg(OH)2
- Reaction with warm water is much slower
- Reaction with steam creates a bright white flame vs reaction with warm water creates no flames
11
Q
What is the trend in reactivity of other group 2 metals with cold water and what do they produce?
A
- Increasing vigour down the group
- Form metal hydroxides
- Alkaline water due to the hydroxides
12
Q
What observations could be made when group 2 metals react with cold water?
A
- Fizzing (more vigorous down the group)
- The metal dissolving (faster down the group)
- The solution heating up (more down the group)
- White precipitate of calcium appearing (less precipitate forms down the group)
13
Q
Group 2 ionic oxides react with water to form (_)
A
Hydroxides
14
Q
Why are the ionic oxides considered basic
A
Because the oxide ions accept protons to become hydroxide ions in this reaction (acting as a bronsted Lowry base)
15
Q
In the reaction,
MgO + H2O -> Mg(OH)2
Mg(OH)2 is only slightly soluble therefore … (comment on products)
A
fewer free OH- ions are produced so lower pH
16
Q
MgO + 2HCl -> …
A
MgCl2 +H2O
17
Q
SrO + 2HCl -> …
A
SrCl2 +H2O
18
Q
CaO + H2SO4 -> …
A
CaSO4 + H2O
19
Q
2HNO3 +Mg(OH)2 -> …
A
Mg(NO3)2 +2H2o
20
Q
2HCl +Mg(OH)2 -> …
A
MgCl2 +2H2O
21
Q
How does the solubility of hydroxides change down the group
A
Group 2 hydroxides become more soluble down the group
22
Q
How do Group 2 hydroxides appear as products (when not soluble)
A
All Group 2 hydroxides when not soluble appear as white precipitates
23
Q
Comment on the solubility of magnesium hydroxide in water
A
insoluble
24
Q
Ionic equation for the formation of Mg(OH)2 (s)
A
Mg2+ (aq) + 2OH- (aq) -> Mg(OH)2 (s)
25
A suspension of magnesium hydroxide in water will appear slightly alkaline (pH 9) so ...
some hydroxide ions must therefore have been produced by a very slight dissolving.
26
State one use of magnesium hydroxide
Medicine, to neutralise excess acid in the stomach and to treat constipation
27
Demonstrate with an equation how magnesium hydroxide neutralises acid in medicine
Mg(OH)2 + 2HCl -> MgCl2 + 2H2O
28
Why is it safe to use magnesium hydroxide in medicine and why is it preferred over calcium carbonate
It is safe to use because it so weakly alkaline. It is preferable to using calcium carbonate as it will not produce carbon dioxide gas.
29
comment on the solubility of calcium hydroxide in water
reasonably soluble
30
describe a use of calcium hydroxide (in agriculture)
to neutralise acidic soils
31
what is an aqueous solution of calcium hydroxide called
limewater
32
Describe the test for carbon dioxide
bubble through limewater - if carbon dioxide is present, limewater will turn cloudy as white calcium carbonate is produced
Ca(OH)2 (aq) + CO2 (g) -> CaCO3 (s) + H2O(l)
33
Comment on the solubility of barium hydroxide in water
easily dissolve (the hydroxide ions present would make the solution strongly alkaline)
34
Comment on the solubility of group 2 sulphates down the group
Group 2 sulphates become less soluble down the group
34
Comment on the solubility of group 2 sulphates down the group
Group 2 sulphates become less soluble down the group
35
Which Group 2 sulphate is the least soluble
BaSO4
36
Explain why barium reacts slowly and only partially with sulfuric acid
If Barium metal is reacted with sufuric acid it will only react slowly as the insoluble barium sulfate produced will cover the surface of the metal and act as a barrier to further attack.
Ba+H2SO4BaSO4 +H2
(The same effect will happen to a lesser extent with metals going up the group as the solubility increases.)
37
What is formed when group 2 metals react with acids such as hydrochloric or nitric acid
form soluble salts
38
What to group 2 carbonates form when they are decomposed by heating
group 2 oxides + carbon dioxide gas
39
define thermal decomposition
the use of heat to break down a reactant into more than one product
40
how does the ease of thermal decomposition vary down the group
the ease decreases down the group
41
why do group 2 carbonates become more thermally stable down the group
As the cations get bigger they have less of a polarising effect and distort the carbonate ion less. The C-O bond is weakened less so it less easily breaks down
42
Why do the group 1 carbonates not decompose apart form lithium?
As they only have +1 charges they don’t have a big enough charge density to polarise the carbonate ion. Lithium is the exception because its ion is small enough to have a polarising effect
43
describe a test that can be carried out to test the ease of thermal decomposition of a carbonate using limewater
heat a known mass of carbonate in a side arm boiling tube and pass the gas produced through lime water. Time for the first permanent cloudiness to appear in the limewater. Repeat for different carbonates using the same moles of carbonate/same volume of limewater/same Bunsen flame and height of tube above flame.
44
what are the products of thermal decomposition of group 2 nitrates (V)
Group 2 nitrates decompose on heating to produce group 2 oxides, oxygen and nitrogen dioxide gas.
45
what would be observed during the thermal decomposition of group 2 nitrates
You would observe brown gas evolving (NO2) and the White nitrate solid is seen to melt to a colourless solution and then re-solidify.
46
how does the ease of thermal decomposition vary down the group of nitrates
ease decreases down the group
47
explain the change in thermal stability of nitrates
Magnesium nitrate decomposes the easiest because the Mg2+ ion is smallest and has the greater charge density. It causes more polarisation of the nitrate anion and weakens the N―O bond
(same as carbonates)
48
Apart from lithium, what do Group 1 nitrates decompose to
nitrate (III) salt + oxygen
(Lithium decomposes in the same way as Group 2 nitrates)
49
Describe the method of a flame test
Use a nichrome wire ( nichrome is an unreactive metal and will not give out any flame colour)
Clean the wire by dipping in concentrated hydrochloric acid and then heating in Bunsen flame
If the sample is not powdered then grind it up.
Dip wire in solid and put in Bunsen flame and observe flame
50
What is the flame test result (colour) for lithium
scarlet red
51
What is the flame test result (colour) for sodium
yellow
52
What is the flame test result (colour) for potassium
Lilac
53
What is the flame test result (colour) for rubidium
red
54
What is the flame test result (colour) for caesium
blue
55
What is the flame test result (colour) for magnesium
no flame colour (energy emitted of a wavelength outside visible spectrum)
56
What is the flame test result (colour) for calcium
brick red
57
What is the flame test result (colour) for strontium
red
58
What is the flame test result (colour) for barium
apple green
59
Explain the occurrence of a flame in a flame test
In a flame test the heat causes the electron to move to a higher energy level.
The electron is unstable at the higher energy level and so drops back down. As it drops back down from the higher to a lower energy level, energy is emitted in the form of visible light energy with the wavelength of the observed light
60
comment on the appearance of fluorine and its reactivity
pale yellow gas, highly reactive
61
comment on the appearance of chlorine and its reactivity
greenish reactive gas, poisonous in high concentrations
62
comment on the appearance of bromine and its reactivity
red liquid, gives off dense brown/orange poisonous fumes
63
comment on the appearance of iodine and its reactivity
shiny grey solid sublimes to purple gas
64
What is the trend in melting and boiling point of halogens down the group
increase
65
Explain the trend in melting and boiling points of halogens
As the molecules become larger they have more electrons and so have larger London forces between the molecules. As the intermolecular forces get larger more energy has to be put into break the forces. This increases the melting and boiling points
66
Define electronegativity
the relative tendency of an atom in a molecule to attract electrons in a covalent bond to itself.
67
What is the trend in electronegativity of halogens down the group
decreases
68
Explain the trend in electronegativity of halogens
As one goes down the group the atomic radii increases due to the increasing number of shells. The nucleus is therefore less able to attract the bonding pair of electrons
69
What is the trend in reactivity of halogens down the group and explain why
The reactivity of the halogens decreases down the group as the atoms get bigger with more shielding so they less easily attract and accept electrons. They therefore form -1 ions less easily down the group
70
what are oxidising agents (in terms of electrons)
electron acceptors
71
How does oxidising strength vary down the group
oxidising strength decreases down the group
72
A halogen that is a strong oxidising agent will (_) a halogen that has a lower oxidising power from one of its compounds
displace
73
chlorine will displace (1) and (2) ions, Bromine will displace (3) ions
1 - bromide
2 - iodide
3 - iodide
74
the colour of the solution in the test tube shows which (_) is present in the solution
free halogen
75
what colour is chlorine in solution
very pale green solution (often colourless)
76
what colour is bromine in solution
yellow solution
77
what colour is iodine in solution
brown solution (sometimes black solid present)
78
what is the colour of the solution when potassium chloride reacts with chlorine
very pale green solution, no reaction
79
what is the colour of the solution when potassium chloride reacts with bromine
yellow solution, no reaction
80
what is the colour of the solution when potassium chloride reacts with iodine
brown solution, no reaction
81
what is the colour of the solution when potassium bromide reacts with chlorine
yellow solution, Cl has displaced Br
82
what is the colour of the solution when potassium bromide reacts with bromine
yellow solution, no reaction
83
what is the colour of the solution when potassium bromide reacts with iodine
brown solution, no reaction
84
what is the colour of the solution when potassium iodide reacts with chlorine
brown solution, Cl has displaced I
85
what is the colour of the solution when potassium iodide reacts with bromine
brown solution, Br has displaced I
86
what is the colour of the solution when potassium iodide reacts with iodine
brown solution, no reaction
87
what is the colour of the solution when potassium chloride reacts with chlorine and an organic solvent is added
colourless, no reaction
88
what is the colour of the solution when potassium chloride reacts with bromine and an organic solvent is added
yellow, no reaction
89
what is the colour of the solution when potassium chloride reacts with iodine and an organic solvent is added
purple, no reaction
90
what is the colour of the solution when potassium bromide reacts with chlorine and an organic solvent is added
yellow, Cl has displaced Br
91
what is the colour of the solution when potassium bromide reacts with bromine and an organic solvent is added
yellow, no reaction
92
what is the colour of the solution when potassium bromide reacts with iodine and an organic solvent is added
purple, no reaction
93
what is the colour of the solution when potassium iodide reacts with chlorine and an organic solvent is added
purple, Cl. has displaced I
94
what is the colour of the solution when potassium iodide reacts with bromine and an organic solvent is added
purple, Br has displaced I
95
what is the colour of the solution when potassium iodide reacts with iodine and an organic solvent is added
Purple, no reaction
96
The colour of the organic solvent layer in the test tube shows which free halogen is present in solution.
What colours are chlorine, bromine and iodine
Chlorine - colourless
Bromine - yellow
Iodine - Purple
97
in all reaction where halogens are reacting with metals, the metals are being (_)
Give the example of Br2 + 2Na -> 2NaBr ( in equation form )
oxidised
2Na -> 2Na+ + 2e-
Br2 + 2e- -> 2Br -
98
Chlorine and bromine can oxidise Fe2+ to Fe3+ however iodine cannot because...
it is not a strong enough oxidising agent
99
What is disproportionation
a reaction where an element simultaneously oxidises and reduces
100
Give the equation for the reaction of chlorine with water
Cl2(g) + H2O(l) -> HClO(aq) + HCl (aq)
101
what are the observations if universal indicator is added after the reaction of chlorine with water
the solution it will first turn red due to the acidity of both reaction products. It will then turn colourless as the HClO bleaches the colour.
102
give a use of chlorine and why it is used despite its toxic effects
Chlorine is used in water treatment to kill bacteria. It has been used to treat drinking water and the water in swimming pools. The benefits to health of water treatment by chlorine outweigh its toxic effects.
103
Cl2, Br2, and I2 in aqueous solutions will react with cold sodium hydroxide. The colour of the halogen solution will fade to (_)
colourless
104
give the equation of chlorine with sodium hydroxide
Cl2(aq) + 2NaOH(aq) -> NaCl(aq) + NaClO(aq) + H2O(l)
105
what is the mixture of NaCl and NaClO used for in life
to disinfect / kill bacteria
106
With hot alkali disproportionation also occurs but the halogen that is oxidised goes to a (_) oxidation state.
higher
107
Name NaClO
Sodium chlorate (I)
108
Name NaClO3
Sodium chlorate (V)
109
Name K2SO4
potassium sulfate (VI)
110
Name K2SO3
potassium sulfate (IV)
111
How does the power of reducing agents vary down the group
The halides show increasing power as reducing agents as one goes down the group.
112
Explain the differing reducing powers of halides
A reducing agent donates electrons.
The reducing power of the halides increases down group 7 They have a greater tendency to donate electrons.
This is because as the ions get bigger it is easier for the outer electrons to be given away as the pull from the nucleus on them becomes smaller.
113
As H2SO4 is not strong enough an oxidising reagent to oxidise the chloride and fluoride ions, what reactions cannot occur and which reaction does occur
No redox reactions occur. Only acid-base reactions occur.
114
Give the equation of sodium fluoride and Sulphuric acid, give observations
NaF(s) + H2SO4(l) -> NaHSO4(s) + HF(g)
Observations: White steamy fumes of HF are evolved.
115
Give the equation of sodium chloride and Sulphuric acid, give observations
NaCl(s) + H2SO4(l) -> NaHSO4(s) + HCl(g)
Observations: White steamy fumes of HCl are evolved.
116
In acid-base reactions, H2SO4 plays the role of ...
an acid (proton donor)
117
Give the equation of the acid base and redox step of the reaction of sodium bromide with sulphuric acid and observations for both steps and give the role of H2SO4 in both steps
Acid-basestep:NaBr(s) + H2SO4(l) -> NaHSO4(s) + HBr(g)
White steamy fumes of HBr are evolved.
H2SO4 acts as an acid (producing HBr)
Redox step: 2HBr + H2SO4 -> Br2(g) + SO2(g) + 2H2O(l)
Red fumes of Bromine are also evolved and a colourless, acidic gas SO2
H2SO4 as an oxidising agent
118
State the equations of Sodium iodide (1) and hydrogen iodide (3) with sulphuric acid along with the observations for each
NaI(s) + H2SO4(l) -> NaHSO4(s) + HI(g)
White steamy fumes of HI are evolved.
2HI + H2SO4 -> I2(s) + SO2(g) + 2H2O(l)
Black solid and purple fumes of Iodine are also evolved
A colourless, acidic gas SO2
6HI + H2SO4 -> 3 I2 + S (s) + 4 H2O (l)
A yellow solid of Sulphur
8HI + H2SO4 -> 4I2(s) + H2S(g) + 4H2O(l)
H2S (Hydrogen Sulphide), a gas with a bad egg smell,
119
What are the reduction products of iodide
sulfur dioxide, sulfur and hydrogen sulfide
120
What is the role of H2SO4 in the four step iodide reaction
H2SO4 plays the role of acid in the first step producing HI and then acts as an oxidising agent in the three redox steps
121
What test is used for halide ions
acidified (with nitric acid) silver nitrate solution
122
What are the results of the silver nitrate test for chloride, bromide and iodide ions
Chloride - white precipitate
Bromide - cream precipitate
Iodide - Yellow precipitate
123
Why is nitric acid added to the silver nitrate when testing for halide ions
The role of nitric acid is to react with any carbonates present to prevent formation of the precipitate Ag2CO3. This would mask the desired observations
124
What is the effect of light on silver halides
The precipitates ( except AgI) darken in sunlight forming silver. This reaction is used in photography to form the dark bits on photographic film
125
What is the effect of ammonia on silver halides
The silver halide precipitates can be treated with ammonia solution to help differentiate between them if the colours look similar
126
What is formed when silver chloride dissolves in dilute ammonia
Silver chloride dissolves in dilute ammonia to form a complex ion
AgCl(s) + 2NH3(aq) -> [Ag(NH3)2]+ (aq) + Cl- (aq)
Colourless solution
127
What is formed when silver bromide dissolves in concentrated ammonia
Silver bromide dissolves in concentrated ammonia to form a
complex ion
AgBr(s) + 2NH3(aq) -> [Ag(NH3)2]+ (aq) + Br - (aq)
Colourless solution
128
What is formed when silver iodide dissolves in concentrated ammonia
Silver iodide does not react with ammonia – it is too insoluble.
129
how are hydrogen halides formed (give the equation of the reaction of NaCl to a hydrogen halide) and observations
Hydrogen halides are made by the reaction of solid sodium halide salts with phosphoric acid
NaCl(s) + H3PO4(l) -> NaH2PO4(s) + HCl(g)
Observations: White steamy fumes of the hydrogen
halides are evolved.
The Steamy fumes of HCl are produced when the HCl meets the air because it dissolves in the moisture in the air
130
Why in the reaction to produce hydrogen halides is a downwards delivery tube used
he downward delivery is used because the hydrogen halides are more dense than air
131
Why is phosphoric acid more suitable to produce hydrogen halides than sulphuric acid
Phosphoric acid is not an oxidising agent and so does not oxidise HBr and HI. Phosphoric acid is more suitable for producing hydrogen halides than using concentrated sulfuric acid to make HCl, HBr, and HI. This is because there are no extra redox reactions taking place and no other products formed.
132
Comment on the solubility of hydrogen halides in water and what is created when they dissolve
The hydrogen halides are all soluble in water. They dissolve to form acidic solutions.
133
When hydrogen halides react with ammonia, what is produced and what are the observations
All the hydrogen halides react readily with ammonia to give the white smoke of the ammonium halide
HCl(g) + NH3 (g) -> NH4Cl (s)
HBr(g) + NH3 (g) -> NH4Br (s)
HI(g) + NH3 (g) -> NH4I (s)
This can be used as a test for the presence of hydrogen halides
134
State the test for carbonate and hydrogencarbonates
Addanydiluteacidandobserveeffervescence.
Bubble gas through limewater to test for CO2 – will turn limewater cloudy
135
State the test for the presence of sulphate
Acidified BaCl2 solution is used as a reagent to test for sulfate ions
If Barium Chloride is added to a solution that contains sulfate ions a white precipitate forms
The acid is needed to react with carbonate impurities that are often found in salts which would form a white Barium carbonate precipitate and so give a false result
136
Why can sulfuric acid not be used as the acid when testing for the presence of sulphates
Sulfuric acid cannot be used to acidify the mixture because it contains sulfate ions which would form a precipitate
137
Describe the test of testing for the presence go halide ions with silver nitrate
This reaction is used as a test to identify which halide ion is present. The test solution is made acidic with nitric acid, and then silver nitrate solution is added dropwise.
The role of nitric acid is to react with any carbonates present to prevent formation of the precipitate Ag2CO3. This would mask the desired observations
138
Give the results of the tests of testing for halide ions with silver nitrate
Fluorides produce no precipitate
Chlorides produce a white precipitate
Ag+(aq) + Cl- (aq) -> AgCl(s)
Bromides produce a cream precipitate
Ag+(aq) + Br- (aq) -> AgBr(s)
Iodides produce a pale yellow precipitate
Ag+(aq) + I- (aq) -> AgI(s)
139
Why can hydrochloric acid not be used when testing for halide ions using silver nitrate
Hydrochloric acid cannot be used to acidify the mixture because it contains chloride ions which would form a precipitate
140
What can the silver halide precipitates be treated with to help differentiate between them if the colours look similar
ammonia solution
141
State the reactions of silver halides with ammonia (and what concentration is required)
Silver chloride dissolves in dilute ammonia to form a complex ion
AgCl(s) + 2NH3(aq) -> [Ag(NH3)2]+ (aq) + Cl- (aq)
Colourless solution
Silver bromide dissolves in concentrated ammonia to form a complex ion
AgBr(s) + 2NH3(aq) -> [Ag(NH3)2]+ (aq) + Br - (aq) Colourless solution
Silver iodide does not react with ammonia – it is too insoluble.
142
Describe the test for cations
Test for ammonium ion NH4+, by reaction with warm NaOH(aq) forming NH3
NH4+ +OH- -> NH3 + H2O
Ammonia gas can be identified by its pungent smell or by turning damp red litmus paper blue
