3.2.3 Group 7(17), the halogens

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  • Created by: KateStoc
  • Created on: 21-05-18 22:05
Explain the trend in electronegativity for the Halogens.
Electronegativity decreases down the group because there is an increase in shell radius so the outer electrons experience more shielding and less pull so it is harder to attract electrons.
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Explain the trend in the boiling point of the elements in terms of their structure and bonding for the Halogens.
Boiling points decrease down the group because the Van der Waals forces increase as the size and Ar of the atomic increases. This is shown in physical states: Fluorine (gas) to Iodine (solid)
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The trend in oxidising ability of the halogens down the group.
Oxidising ability decreases down the group. Chlorine is the top oxidiser and Iodine is the worst.
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Displacement reactions of halide ions in aqueous solution (Written).
Chlorine Water displaces KBr (orange solution) and KI (Brown solution). Bromine water displaces KI (brown solution)
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Displacement reactions of halide ions in aqueous solution (Symbols).
Cl2(aq) + 2KBr/I (aq) -> 2KCl(aq) + Br2/I2(aq). Br2(aq) + 2KI(aq) -> 2KBr(aq) + I2(aq)
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The trend in reducing ability of the halide ions.
Reducing ablility increases down the group. Iodine is the best reducing agent and Chlorine is the worse.
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Reactions of solid sodium halides with concentrated sulfuric acid (generic symbols).
NaX + H2SO4 -> NaHSO4 + HX
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Reactions of solid sodium halides with concentrated sulfuric acid (written).
All Halides react with concentrated sulfuric acid to get a hydrogen halide. Some halide ions are strong enough to reduce the sulfuric acid to water and sulfuric dioxide. Iodide will reduce the SO2 to H2S or S.
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Reactions of solid sodium iodide with concentrated sulfuric acid (symbols).
NaI(s) + H2SO4(l) -> NaHSO4(s) + HI(g). 2HI(g) + H2SO4(l) -> I2(s) + SO2(g) + 2H2O(l). 6HI(g) + SO2(g) -> H2S(g) + 3I2(s) + 2H2O(l)
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The use of acidified silver nitrate solution to identify and distinguish between halide ions (Written).
Add dilute nitric acid to remove unneeded ions. Then add silver nitrate solution. Fluoride gives no ppt (soluble) Chloride ions gives a white ppt, Bromide ion gives a cream ppt, Iodide ion gives a yellow precipitate.
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The use of acidified silver nitrate solution to identify and distinguish between halide ions (symbols).
Ag+(aq) + X-(aq) -> AgX(aq)
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The trend in solubility of the silver halides in ammonia.
The solubility of halide ions decreases down the group. Cl- dissolves in dilute ammonia, Br- dissolves in concentrated ammonia, I- is insoluble.
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The reaction of chlorine with water (Written).
When chlorine gas reacts with water, it is a reversible reaction to form H+ ions, chloride ions and chlorate (I). If in sunlight Cl- ions and oxygen forms.
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The reaction of chlorine with water (Symbols).
Cl2(g) + H2O(l) 2H+(aq) + Cl-(aq) +ClO-(aq).
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The reaction of chlorine with water in the presence of sunlight (Written).
When chlorine reacts with water in sunlight, H+ ions, Cl- ions and oxygen forms.
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The reaction of chlorine with water in the presence of sunlight (symbols).
Cl2(g) + H2O(l) 2H+(aq) + 2Cl-(aq) + 1/2O2(g)
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The use of chlorine in water treatment.
Chlorate (I) ions kill bacteria. So by adding it, it makes the water safe to drink.
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The issues of using chlorine to treat water.
Chlorine reacts with organic compounds to produce carcinogens (cancer-causing).
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Appreciate that the benefits to health of water treatment by chlorine outweigh its toxic effects.
The small risks of cancer is outweighed by the risk of an epidemic if left untreated.
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The reaction of chlorine with cold, dilute, aqueous NaOH (Written)
When chlorine gas is mixed sodium hydroxide produces sodium chlorate (I) solution. This is household bleach.
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Uses of NaClO.
NaClO is bleach, and in water treatment and to bleach paper and textile.
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The reaction of chlorine with cold, dilute, aqueous NaOH (symbols)
2NaOH(aq) + Cl2(g) -> NaClO(aq) + NaCl (aq) + H2O(l)
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Card 2

Front

Boiling points decrease down the group because the Van der Waals forces increase as the size and Ar of the atomic increases. This is shown in physical states: Fluorine (gas) to Iodine (solid)

Back

Explain the trend in the boiling point of the elements in terms of their structure and bonding for the Halogens.

Card 3

Front

Oxidising ability decreases down the group. Chlorine is the top oxidiser and Iodine is the worst.

Back

Preview of the back of card 3

Card 4

Front

Chlorine Water displaces KBr (orange solution) and KI (Brown solution). Bromine water displaces KI (brown solution)

Back

Preview of the back of card 4

Card 5

Front

Cl2(aq) + 2KBr/I (aq) -> 2KCl(aq) + Br2/I2(aq). Br2(aq) + 2KI(aq) -> 2KBr(aq) + I2(aq)

Back

Preview of the back of card 5
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