Inorganic chemistry and the periodic table Flashcards
(67 cards)
1
Q
Why does ionisation energy decrease down group 2 ?
A
- Each element down has an extra electron shell compared to the one above.
- The extra inner shells shield the outer electrons from the attraction of the nucleus.
- The extra shell also mean the outer electrons are further from the nucleus, which greatly reduces the electrostatic attraction between the nucleus and outer electrons.
- So it’s easier to remove outer electrons, meaning the ionisation energy decreases down group 2.
2
Q
What is the equation for group 2 metals reacting with water?
A
M (s) + 2H2O (l) → M(OH)2 (aq) + H2 (g)
3
Q
How do these metals react with water:
Be
Mg
Ca
Sr
Ba
A
Be - doesn’t react
Mg - very slowly
Ca - steadily
Sr - fairly quickly
Ba - rapidly
4
Q
What is the equation for group 2 metals burning in oxygen?
A
M (s) + Cl2 (g) → MCl2 (s)
5
Q
What is the equation for metal oxides reacting with water?
A
MO (s) + H2O (l) → M(OH)2 (aq)
6
Q
What is the equation for metal oxides reacting with dilute acid?
A
MO (s) + 2HCl (aq) → MCl2 (aq) + H2O (l)
7
Q
What is the equation for metal hydroxides reacting with water?
A
M(OH)2 (aq) → M(OH)2 (aq)
8
Q
What is the equation for metal hydroxides reacting with dilute acid?
A
M(OH)2 (aq) + 2HCl (aq) → MCl2 (aq) + 2H2O (l)
9
Q
What is the solubility trend for group 2 hydroxides?
A
Solubility increases down the group
10
Q
What is the solubility trend for group 2 sulfates?
A
Solubility decreases down the group
11
Q
Most group 2 sulfates are soluble in water except…
A
Barium sulfate
12
Q
What is thermal decomposition?
A
When a substance breaks down (decomposes) when heated. The more thermally stable a substance is, the more heat it will take to break down.
13
Q
Describe how group 2 carbonates are distorted.
A
- The carbonate and nitrate ions are large anions and can be made unstable by the presence of a cation.
- The cation polarises the anion, distorting it. The greater the distortion, the less stable the compound.
14
Q
Explain the trend in thermal stability of group 2 carbonate/nitrate compound.
A
- Large cations cause less distortion than small cations, as they have a lower charge density (the charge on the ion is spread over a large area).
- So the further down the group, the larger the cations, the lower the charge density so less distortion caused and the more stable the carbonate/ nitrate compound.
- So thermal stability increases down a group.
15
Q
Why are group 2 compounds less thermally stable than group 1 compounds?
A
- The greater the charge on the cation, the greater the distortion and the less stable the carbonate/nitrate compound becomes.
- Group 2 cations have a 2+ charge, compared to 1+ charge for group 2 cations.
- So group 2 carbonates and nitrates are less stable than those in group 1.
16
Q
What do group 2 carbonates form when they decompose?
A
- the metal oxide
- carbon dioxide
17
Q
What do group 2 nitrates form when they decompose?
A
- the metal oxide
- nitrogen dioxide
- oxygen
18
Q
What do group 1 carbonates form when they decompose?
A
They are thermally stable, you can’t heat them enough with a bunsen burner to decompose.
Except Li2CO3 (lithium carbonate) which decomposes to lithium oxide and carbon dioxide.
19
Q
What do group 1 nitrates form when they decompose?
A
- the metal nitrite (MNO2)
- oxygen
- except lithium nitrate, which decomposes to form lithium oxide, nitrogen dioxide and oxygen.
20
Q
How can you test the thermal stability of nitrates?
A
- How long it takes for enough O2 to be produced (enough to relight a glowing splint)
- How long it takes until an amount of brown gas (NO2) is produced. This needs to be done in a fume cupboard because NO2 is toxic.
21
Q
How can you test the thermal stability of carbonates?
A
- How long it takes for an amount of CO2 to be produced.
- You test for carbon using limewater (saturated solution of calcium hydroxide). This turns cloudy with CO2.
22
Q
What are the flame colours of these group 1 and 2 metals and their compounds:
Li
Na
K
Rb
Cs
Ca
Sr
Ba
A
Li - red
Na - yellow/orange
K - lilac
Rb - red
Cs - blue
Ca - brick red
Sr - crimson
Ba - green
23
Q
What’s the method for doing a flame test?
A
- Heat a piece of platinum wire in a hot bunsen flame to clean it.
- Dip the platinum wire in the HCl.
- Dip the wire into the compound mixture and hold it in a flame and note the colour produced.
24
Q
Why do we see different flame colours for different group 1 and 2 compounds?
A
- The energy absorbed from the flame causes electrons to move to higher energy level.
- The colours are seen as the electrons fall back down to lower energy levels, releasing energy in the form of light.
- The difference in energy between the higher and lower levels determines the wavelength of the light released, which determines the colour of the light.
25
What is the colour and state of fluorine at room temperature?
Pale yellow gas
26
What is the colour and state of chlorine at room temperature?
Green gas
27
What is the colour and state of bromine at room temperature?
Red/brown liquid
28
What is the colour and state of iodine at room temperature?
Grey solid
29
What is the electronegativity trend down group 7?
Decreases down the group
30
What is the colour of chlorine, bromine and iodine in water?
chlorine - virtually colourless
bromine - yellow/orange
iodine - brown
31
What is the colour of chlorine, bromine and iodine in hexane?
chlorine - virtually colourless
bromine - orange/red
iodine - pink/violet
32
Explain why halogens get less reactive down the group
- They usually react by gaining an electron in their outer p-subshell.
- As they're reduced, they oxidise another substance.
- As you go down the group, their atoms get larger, so their outer electrons are further from the nucleus, and there's more shielding.
- So it gets harder for larger halogens to attract the last electron and form a full outer shell.
33
Explain the trend in electronegativity for halogenoalkanes.
- Electronegativity is a measure of how well an atom attracts electrons in a covalent bond.
- Electronegativity decreases down group 7 due to the increase in the number of inner electron shells and the increase in distance between the nucleus and the bonding electron.
34
Why does mpt/bpt increase down group 7?
- There's an increase in electron shells (and therefore electrons). So the London forces between the halogen molecules get stronger.
- The increase in London forces makes it harder to overcome the intermolecular forces, and so mpt and bpt also increase.
35
Why do we predict the behavior of fluorine and astatine by looking at the trends in the behavior of the other halogens?
The chemistry of fluorine and astatine is hard to study, due to fluorine being a toxic gas and astatine is highly radioactive, so decays quickly.
36
What is a displacement reaction?
A type of reaction where 1 element replaces another element in a compound.
37
Which of these halogens will displace each other:
Chlorine
Bromine
Iodine
Chlorine - Will displace both Br- and I- ions.
Bromine - Will displace I- ions but not Cl- ions.
Iodine - Will not displace Br- or Cl- ions.
38
What colour is:
chlorine water
bromine water
iodine water
chlorine water - colourless
bromine water - orange
iodine water - brown
39
KCl (aq) is reacted with chlorine, bromine and iodine water. What does it react with?
No reaction in all of them
40
KBr (aq) is reacted with chlorine, bromine and iodine water. What does it react with?
bromine water - no reaction
iodine solution - no reaction
chlorine water - Cl2 (aq) +2Br- (aq) → 2Cl- (aq) + Br2 (aq)
41
KI (aq) is reacted with chlorine, bromine and iodine water.
bromine water - Br2 (aq) +2I- (aq) → 2Br- (aq) + I2 (aq)
iodine solution - no reaction
chlorine water - Cl2 (aq) +2I- (aq) → 2Cl- (aq) + I2 (aq)
42
What's the colour change if bromide is displaced and bromine is formed?
Orange
43
What's the colour change if iodide is displaced and iodine is formed?
Brown
44
How can you make the colour changes during halogen displacement reactions easier to see?
- Shake the reaction mixture with an organic solvent like hexane.
- The halogen present will dissolve i the organic solvent, which settles out as a distinct layer above the aqueous solution.
45
What is the equation for halogens (fluorine) reacting with group 1 metals (lithium)? What's oxidised/reduced?
2Li (s) + F2 (g) → 2LiF (s)
Lithium is oxidised by 1 and fluorine is reduced by 1.
46
What is the equation for halogens (chlorine) reacting with group 2 metals (magnesium)? What's oxidised/reduced?
Mg (s) + Cl2 (g) → MgCl2 (s)
Magnesium is oxidised by 2 and chlorine is reduced by 1.
47
What's the disproportionation reaction between halogens and cold alkalis?
X2 + 2NaOH → NaOX + NaX + H2O
48
What oxidation states can chlorine exist in?
Cl- chloride
Cl chlorine
ClO- chlorate(I)
49
What oxidation states can bromine exist in?
BrO- bromate(I)
BrO2 - bromate(III)
50
What oxidation states can iodine exist in?
IO3 - iodate(V)
IO4 - iodate(VII)
51
How is bleach formed from chlorine gas and cold, dilute aqueous NaOH?
2NaOH (aq) + Cl2 (g) → NaClO (aq) + NaCl (aq) + H2O (l)
52
What are some uses of bleach?
Water treatment
Bleach paper/textiles
Cleaning toilets
53
What's the disproportionation reaction between halogens and hot alkalis?
3X2 + 6NaOH → NaXO3 + 5NaX + 3H2O
54
What reactions happen when you add chlorine to water which make it safe to drink and swim in?
Cl2 (g) + H2O (l) ⇌ HCl (aq) + HClO (aq)
HClO (aq) + H2O (l) ⇌ ClO- (aq) + H3O+ (aq)
ClO- ions (chlorate (I) ions) kill bacteria.
55
Why does the reducing power of halides increase down the group?
- A halide ion can act as a reducing agent by losing an electron from its outer shell. How easy this is depends on the attraction between the halide's nucleus and the outer electrons. The attraction decreases down the group due to:
- the ion gets bigger, so electrons are further from the +ve nucleus.
- There are extra inner electron shells, so there's more shielding.
56
What can we react halides with to test their reducing power?
Sulfuric acid
57
What is the reaction of KF and KCl with H2SO4?
Why does the reaction stop there?
What can you see?
KF (s) + H2SO4 (l) → KHSO4 (s) + HF (g)
KCl (s) + H2SO4 (l) → KHSO4 (s) + HCl (g)
fluoride and chloride ions aren't strong enough reducing agents to reduce the H2SO4, so this isn't a redox reaction due to the oxidation numbers of the halide and sulfur staying the same.
Misty fumes when the gas comes in contact with the moisture in the air.
58
What are the equations for KBr reacting with H2SO4?
KBr (s) + H2SO4 (l) → KHSO4 (s) + HBr (g)
Gives misty fumes of HBr. Br- ions are a stronger reducing agent than Cl- ions and react with the H2SO4 in a redox reaction.
2HBr (aq) + H2SO4 (l) → Br2 (g) + SO2 (g) + 2H2O (l) Sulfur reduced from +6 to +4. Br oxidised from -1 to 0.
The reaction produces choking fumes of SO2 and orange fumes of Br2.
59
What are the equations for KI reacting with H2SO4?
KI (s) + H2SO4 (l) → KHSO4 (s) + HI (g)
I- ions then reduce H2SO4.
2HI (g) + H2SO4 (l) → I2 (s) + SO2 (g) + 2H2O (l) S reduced from +6 to +4. I oxidised from -1 to 0. The I- keeps going and reduces the SO2 to H2S.
6HI (g) + SO2 (g) → H2S (g) + 3I2 (s) + 2H2O (l) S reduced from +2 to -2. I oxidised from -1 to 0.
60
What can you see when hydrogen halides dissolve in water? (include a test)
Misty fumes of acidic gas which turn damp blue litmus paper red.
61
What acids do hydrogen chloride, bromide and iodide form?
Hydrochloric acid
Hydrobromic acid
Hydroiodic acid
62
What can you see when hydrogen halides react with ammonia gas? Include an equation for HCl
White fumes
NH3 (g) + HCl (g) → NH4Cl (s)
63
How can we test for carbonate and hydrogen carbonate ions?
React them with hydrochloric acid, they will fizz because they give off CO2.
Water will also be produced.
64
Test for CO2?
Bubble the gas through limewater, it will turn cloudy.
65
Test for sulfates?
Add dilute HCl, followed by barium chloride solution. If a white precipitate of barium sulfate forms, the original compound contained a sulfate.
66
Test for ammonia gas?
Ammonia gas turns damp red litmus paper blue.
67
Test for ammonium ions?
Add sodium hydroxide and gently heat the mixture. If ammonia is given off (turning red litmus paper blue) there are ammonium ions in the substance.
NH4Cl (aq) + NaOH (aq) → NH3 (g) + H2O (l) + NaCl (aq)
