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Name the four first halogens?
Fluorine, chlorine, bromine, Iodine
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At room temperature what colour is…
- Fluorine?
- Chlorine?
- Bromine?
- Iodine?
- Yellow
- Green
- Red brown
- Black
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What are the gaseous colours of…
- Fluorine?
- Chlorine?
- Bromine?
- Iodine?
- Yellow
- Green
- Red orange
- Purple
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Describe the halogens.
The halogens are non-metal diatomic molecules
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How do the melting/boiling points of the halogens change going down the group?
They increase, due to the larger atoms having more electrons, making the Van Der Waals forces between molecules stronger and therefore more energy is needed to overcome these forces
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Which halogen has many untypical properties?
- Why is this?
- How does fluorines size effect this?
- Why can we not investigate fluorine in aqueous solution?
- Fluorine
- Because the F-F Bond is very weak
- It's small size leads to repulsion between non-bonding electrons due to their close proximity
- Because it reacts with water
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Why is the Potassium iodide often added to table salt?
Because it is necessary for the normal functioning of the thyroid gland
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How does the electronegativity of the halogens change as you go down the group?
It decreases as you go down the group because distance between shared electrons and positive nuclei increases. Meaning there is more shielding therefore there is weaker attraction by nucleus on bonding pair of electrons in the covalent bond. And these factors are more important than the increasing nuclear charge.
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How do halogens usually react?
- In terms of redox halogens are what?
- By gaining electrons to become negative halide ions Oxidising agents that are reduced
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How does the oxidising ability change going down the group?
- What does this make fluorine?
- It decreases, One of the most powerful oxidising agents known
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How are halide ions reducing agents?What is this trend linked to?
- They will lose one of their electrons to become a halogen molecule,
- The size of the ion, The larger the ion the more easily electron is lost because it will have a lower electronegativity
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What occurs during their displacement reactions?
- What trend does a displacement reaction usually follow?
- Halogens will react with the metal halide in a solution in such a way that the halide in this compound will be displaced by the more reactive halogen
- A halogen will displace the halide ion of the halogen below it
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Give the general equation for the displacement of bromide ions in a metal solution by chlorine?
Give the ionic equation?What is reduced?
Cl2 + 2NaBr ---> 2NaCl + Br2
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The extraction of bromine from sea water is an example of what?
- Sea water contains small amounts of bromine ions, oxidised by what?
- To produce?
- What is the equation?
The oxidation of a halide by a halogen
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Bromine
Cl2 + 2Br- ----> Br2 + 2Cl-
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How do the sizes of the halogen atoms change as you go down the group?
They get bigger because each element has one extra filled main level of electrons to the one above
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What is the equation for the extraction of iodine from kelp?Explain how it is extracted.
2I- + MnO2 + 4H+ ----> Mn2+ + 2H20 + I2
It is washed with water then the residue is heated with manganese oxide
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When are halide ions reducing agents?How does the reducing power change going down the group?
When solid sodium halides react with concentrated sulphuric acid.It increases
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What happens during the reaction of sodium chloride and concentrated sulphuric acid?
- What is the product produced?
- What is the equation?
- Type of reaction is this?
- Why is it not a redox reaction?When does a similar reaction occur?
Drops of H2SO4 are added to the solid sodium chloride and steamy fumes of hydrogen chloride can be seen
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NaCl + H2SO4 ---> NaHSO4 + HCl
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No oxidation state has changed because the chlorine ion is too weak to reduce the sulfur in Sulfuric acid
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With sodium fluoride to produce hydrogen fluoride
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What are the dangers of hydrogen fluoride?
It is extremely dangerous gas that will etch glass
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What is the ionic equation for the reaction of sodium chloride with sulfuric acid?
Why is this not a redox reaction?
+1 -1 +1 +6 -2 +1 +1 +6 -2 +1 -1NaCl + H2SO4 ----> NaHSO4 + HCl
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Because no oxidation state has changed
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What is observed in the reactions of solid sodium bromide and H2SO4?
Steamy fumes of hydrogen bromide and brown fumes of bromine are observed, colourless sulphur dioxide is also formed.
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How many reactions occur when sodium bromide reacts with conc. sulfuric acid?
- What are these?
- What is the oxidation state of the sulfur reduced from and to?
- What does the oxidation state of bromine increase from and to?
- Two First sodium hydrogensulphate and hydrogen bromide are produced in a similar acid-base reaction to the sodium chloride reaction.However bromide ions are strong enough reducing agents to reduce the sulfuric acid to sulfur dioxide.From +6 to +4 -1 to 0
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In the reactions of sodium bromide and concentrated sulphuric acid, what are the equations?
Which is the redox reaction?
Is the reaction endo or exothermic?
What happens to some of the Bromine?
NaBr + H2SO4 ----> HBr + NaHSO4
2H+ + 2Br- + H2SO4 ----> SO2 + 2H2O + Br2
The second
Exothermic
It vaporises
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What is observed in the reaction of solid sodium Iodide and concentrated H2SO4?What colourless gas is also evolved?
- Steamy fumes of hydrogen iodide is observed, Black solid iodine appears, the bad egg smell of hydrogen sulphide gas is present, and yellow solid sulphur may also be seen.
- Sulfur dioxide (SO2)
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Several reactions occur when sodium iodide reacts with H2SO4, what occurs in the first reaction?
- Give the equation.What happens next, refer to the reducing ability of iodide ions.As the sulfur passes through oxidation state zero what may appear?What is the equation for this reaction? (-2) Write the oxidation states below.
- NaI + H2SO4 ----> HI + NaHSO4
- Because iodide ions are better reducing agents than bromide ions, they reduce the sulfur in sulfuric acid even further from +6 to 0 then -2
- Yellow solid sulfur
- 8H+ + 8I- + H2SO4 ----> H2S + 4H2O + 4I2 -1 +6 -2
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