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Chemistry A - Level > Topic 4 (Group 7) - Inorganic Chemistry and the Periodic Table > Flashcards

Topic 4 (Group 7) - Inorganic Chemistry and the Periodic Table Flashcards

1
Q

What are the group 7 elements on the periodic table called?

A

the halogens

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2
Q

Describe the trend in atomic radii down group 7 elements

A

The atomic radius increases due to additional filled inner shells

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3
Q

Describe the trend in electronegativity down the group 7 elements

A
  • The atomic radius increases
  • The strength of shielding increases
  • Electrons are less strongly attracted to the nucleus
  • Electronegativity decreases
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4
Q

What is the definition of electronegativity?

A

The measure of the tendency of an atom to attract a bonding pair of electrons

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5
Q

Describe the trend in reactivity down the group 7 elements

A

Reactivity decreases
- Halogens need to gain an electron in order to have a full outer shell
- As you go down the group the effective nuclear charge decreases as shielding increases
- Less attraction between the nucleus and an electron

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6
Q

Describe the trend in boiling points down the group 7 elements

A

Boiling/ Melting Point increases as you go down the group
- the number of electrons per molecule increases
- the strength of the London Forces increases
- more energy is required to overcome them

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7
Q

What structure do halogen molecules have?

A

Simple molecular

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8
Q

What does is chlorines’ state and appearance at RTP?

A

yellow/green gas

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9
Q

What is bromines’ state and appearance at RTP?

A

dark red liquid

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10
Q

What is iodines’ state and appearance at RTP?

A

dark grey solid

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11
Q

What is astatines’ state and appearance at RTP?

A

black solid

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12
Q

What is the definition of a redox reaction?

A

One where both oxidation and reduction occur in the same reaction

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13
Q

What is the reaction that shows the trend in reactivity of Halogens?

A

Displacement reaction

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14
Q

What is the colour of Chloride ions in solution?

A

yellow

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15
Q

What is the colour of Bromide ions in solution?

A

orange

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16
Q

What is the colour of Iodide ions in solution?

A

brown

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17
Q

What are Displacement reactions of Halogens normally carried out in?

A

An organic solvent such as cyclohexane

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18
Q

Why are displacement reactions of halogens carried out in cyclohexane?

A

As this makes the colours easier to distinguish

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19
Q

Write the full equation + ionic equation and describe what happens when sodium chloride is put in a solution of bromine

A

NO REACTION - Bromine is less reactive than chlorine therefore the solution sustains orange

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20
Q

Write the full equation + ionic equation and describe what happens when sodium bromide is put in a solution of chlorine

A

REACTION - Chlorine is more reactive than bromine therefore, a displacement reaction occurs and the solution turns orange (from yellow)

2NaBr(aq) + Cl2 (aq) -> 2NaCl (aq) + Br2 (aq)

2Br(-) (aq) + Cl2 (aq) -> 2Cl(-) (aq) + Br2 (aq)

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21
Q

Write the full equation + ionic equation and describe what happens when sodium iodide is put in a solution of chlorine

A

REACTION - Chlorine is more reactive than iodine therefore, a displacement reaction occurs and the solution turns brown (from yellow)

2NaI(aq) + Cl2 (aq) -> 2NaCl (aq) + I2 (aq)

2I(-) (aq) + Cl2 (aq) -> 2Cl(-) (aq) + I2 (aq)

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22
Q

Write the full equation + ionic equation and describe what happens when sodium iodide is put in a solution of bromine

A

REACTION - Bromine is more reactive than iodine therefore, a displacement reaction occurs and the solution turns brown (from orange)

2NaI(aq) + Br2 (aq) -> 2NaBr (aq) + I2 (aq)

2I(-) (aq) + Br2 (aq) -> 2Br(-) (aq) + I2 (aq)

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23
Q

What is the colour change when cyclohexane is added to a solution containing bromide ions?

A

orange -> stronger orange

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24
Q

What is the colour change when cyclohexane is added to a solution containing Iodide ions?

A

brown -> pink

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25
What do halogens act as when being reacted with group 1 and 2 metals?
oxidising agents (they themselves are reduced)
26
Write an example equation of the reaction of fluorine with lithium? What are the oxidation states of each of the species?
2Li (s) + F2 (g) -> 2LiF (s) Li: 0 -> +1 F2: 0 -> -1 (Fluorine atoms are reduced to fluoride ions)
27
What are Halide ions good at?
Being reducing agents
28
Why are halide ions good reducing agents?
As they are able to donate electrons to the species being reduced
29
How does the reducing power of halide ions change as you descend the group? Why?
The reducing power increases. This is because the valence electron is less attracted to the nucleus as it is further away from the and there is increased shielding.
30
How would you test for halide ions present in solution?
- If you have a solid when testing for the presence of halide ions you must first dissolve the solid in water - Add nitric acid to remove any carbonate impurities that could produce a false positive - Add silver nitrate solution - A coloured ppt. will form depending on the halide ion present in the compound
31
What are the coloured ppt. formed for each of the halides?
Chloride ions (Silver Chloride) - white ppt. Bromide ions (Silver Bromide) - cream ppt. Iodide ions (Silver Iodide) - yellow ppt.
32
Write a full equation and an ionic equation to show a positive result in a test for halides e.g using NaCl
AgNO3 (aq) + NaCl (aq) -> AgCl (s) + NaNO3 (aq)
33
Why doesn't the halide test work for fluorine?
As silver fluoride is soluble, no ppt. formed
34
Why do you have to do a further test on halides after adding silver nitrate?
As the colour of the ppt.'s can be hard to observe
35
What is the second part of the test for halides?
Adding dilute and then conc. ammonia to the solutions
36
Which silver halides dissolve in dilute ammonia?
Silver Chloride
37
Which silver halides dissolve in conc. ammonia?
Silver Bromide and Silver Chloride
38
Which silver halides wont dissolve in either dilute or conc. ammonia?
Silver Iodide
39
What reaction shows the trend in the reducing ability of halides?
group 1 halide + sulphuric acid (H2SO4)
40
What is sulphuric acid?
A strong oxidising agent
41
Why do we use conc. sulphuric acid when testing for the trend in the reducing ability of halides?
As it is a compound that can be reduced by different amounts depending on the strength of the reducing agent
42
Write the equation for the reaction of NaCl with conc. H2SO4
NaCl + H2SO4 -> HCl + NaHSO4
43
What are the observations in the reaction of NaCl with conc. H2SO4, including further tests with damp blue litmus, ammonia gas and acidified potassium dichromate?
OBSERVATIONS HCl gas - Steamy fumes FURTHER TESTS Potassium dichromate - remains orange (has not been reduced) Damp blue litmus - turns red as HCl gas produced Ammonia - HCl + NH3 -> NH4Cl which produces a white smoke
44
What are the oxidation states of the species in the reaction of NaCl with conc. H2SO4?
Not a redox reaction, no change in oxidation states Sulphur = +6 before and after
45
How do you know that HCl has not been oxidised to chlorine in the reaction of NaCl with H2SO4?
As damp blue litmus paper is not bleached
46
Write the equations for the reaction of NaBr with conc. H2SO4
NaBr + H2SO4 -> HBr + NaHSO4 sulphur is reduced further 2HBr + H2SO4 -> Br2 + SO2 + 2H2O
47
What are the observations in the reaction of NaBr with conc. H2SO4, including further tests with damp blue litmus, ammonia gas and acidified potassium dichromate?
OBSERVATIONS HBr gas - Steamy fumes Br2 gas - Orange gas FURTHER TESTS Potassium Dichromate - turns from orange to green/blue as is reduced Damp blue litmus - turns red as HBr gas produced Ammonia - HBr + NH3 -> NH4Br which produces a white smoke
48
What are the oxidation states of the species in the reaction of NaBr with conc. H2SO4?
2nd Reaction Sulphur: +6 -> +4 Bromine: -1 -> 0
49
Write the equations for the reaction of NaI with conc. H2SO4
H2SO4 + NaI -> HI + NaHSO4 small intermediate step 2HI + H2SO4 -> I2 + SO2 + 2H2O final step 6HI + SO2 -> H2S + 3I2 + 2H2O
50
What are the observations in the reaction of NaI with conc. H2SO4, including further tests with damp blue litmus, ammonia gas and acidified potassium dichromate?
OBSERVATIONS HI gas - steamy fumes H2S - smell of rotten eggs I2 gas - purple vapour I2 solid - purple/black solid neck deposit FURTHER TESTS Potassium dichromate - Sustains orange as no SO2 produced Damp blue litmus paper - not making any acidic product as no HI gas Ammonia - no white smoke produced as no HI gas left
51
What are the oxidation states of the species in the reaction of NaI with conc. H2SO4?
First reaction no oxidation state changes Second reaction +6 -> +4 Third Reaction (some sulphur deposits) +4 -> 0 Final Reaction 0 -> -2
52
What is the definition of a disproportionation reaction?
When the same species is both reduced and oxidised in one reaction
53
What are the 2 day to day uses of Chlorine?
- As a disinfectant in water to make it suitable for drinking - As a primary element of bleach
54
Write the equation for chlorine when it is used as a disinfectant
Cl2 (aq) + H2O (l) -> HCl + HClO
55
What are the names and oxidation states of the ions for the reaction when chlorine is used as a disinfectant
Cl2 - 0 Cl in HCl - -1 Cl in HClO - +1 NB: ClO- is a chlorate (I) ion
56
Write the equation of how bromine reacts with water
Br2 (aq) + H2O (l) -> HBr + HBrO
57
Write the disproportionation equation to produce an ingredient of bleach
Cl2(aq) + NaOH(aq) -> NaCl(aq) + NaClO(aq) + H2O(l)
58
What are the conditions for the reaction with the equation: Cl2(aq) + NaOH(aq) -> NaCl(aq) + NaClO(aq) + H2O(l)
cold (room temperature) alkaline
59
What is the ionic equation for the reaction of chlorine with cold aqueous alkali and the oxidation states of chlorine in each of its species?
Cl2 + 2OH- -> Cl- + ClO- + H2O Cl2- 0 Cl- -1 ClO- - +1
60
Write the disproportionation reaction equation for when chlorine reacts with hot, concentrated NaOH
3Cl2(aq) + 6NaOH(aq) -> 5NaCl(aq) + NaClO3(aq) + 3H2O(l)
61
Write the ionic equation for when chlorine reacts with hot, concentrated NaOH and the oxidation states of chlorine in each of its species
3Cl2 + 6OH- -> 5Cl- + ClO3- + 3H2O
62
Will BrO- and IO- disproportionate at lower or higher temperatures than ClO-
lower temperatures as they are less stable
63
What do hydrogen halides act as in solution?
strong acids
64
Write the equation for the reaction of a hydrogen halide with ammonia
HCl + NH3 -> NH4Cl HBr + NH3 -> NH4Br HI + NH3 -> NH4I
65
Write the equation for the reaction of a hydrogen halide with water
HCl + H2O -> Cl- + H3O+ HBr + H2O -> Br- + H3O+ HI + H2O -> I- + H3O+
66
What pH is the resulting solution when hydrogen halides are reacted with water
acidic
67
What ions are formed when hydrogen halides are reacted with water? Why?
Hydroxonium ion Halide ion The hydrogen halide will dissociate full into its ions in solution. The OH- ions in the water molecule act as a base and accept the H+ ions.
68
What is the trend in acid like behaviour down the group of hydrogen halides? Why?
The acid behaviour increases down the group. In order to behave as an acid the molecule has to be able to dissociate and, therefore, acid behaviour is dependant on how easy it is to break the bond within the molecule. The bond enthalpy decreases down the group which is why acid behaviour increases.
69
What is the trend in boiling point down the group of hydrogen halides? Why?
Boiling point is high at HF, then drops to HCl and then increases down the group HF - Hydrogen bonding, PDD forces, low LF's HCl -> HI whilst PDD forces are decreasing this is outweighed by the increase in the number of electrons and therefore the increase in LF's
70
How do you test for the presence of sulphate ions?
- If compound you are testing is not in solution, first dissolve it in pure water - Add HCl - Add BaCl - If sulphate ions are present then a white ppt. will form
71
Write a full general equation for the test for sulphate ions
BaCl2 + XSO4 -> BaSO4 + XCl2
72
Write an ionic equation for the test for sulphate ions
Ba(2+) aq + SO4(2-) aq -> BaSO4(s)
73
Why do we add acid before adding BaCl2 in the test for sulphate ions?
Barium carbonate is also an insoluble compound, therefore if you added BaCl2 to a solution of Na2CO3 then the insoluble white ppt. barium carbonate would form giving a false positive for the test for the sulphate ion. The acid reacts with the carbonate ions -> salt + CO2 + H2O 2HCl + X2CO3 ->2XCl (aq) + CO2 +H2O
74
How do you test for the presence of carbonate or hydrogencarbonate ions?
- Add HCl to the substance containing carbonate ions - If the substance contains CO3(2-) ions or HCO3(-) ions then CO2 gas will be produced and there will be effervescence - To confirm that CO2 gas has been produced you would bubble the gas through limewater
75
What is the general equation in the test for carbonate ions?
XCO3 + 2HCl -> CO2 + H2O + XCl2
76
How do you test for ammonium ions?
- Add sodium hydroxide solution (NaOH) and gently warm - If the compound contains ammonium ions then ammonia gas will be produced which you can test for as it will turn damp red litmus paper blue
77
Does the test for ammonium ions matter if the compound is in a solid or liquid state?
No
78
Write the ionic equation for the test for ammonium ions
NH4(+) (aq or s) + OH(-) (aq) -> NH3 (g) + H2O (l)
79
Write the equation for the test for ammonium ions with ammonium chloride
NH4Cl + NaOH -> NaCl + NH3 + H2O

Chemistry A - Level (26 decks)

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