Chemistry group 7

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  • Created by: I.m
  • Created on: 17-12-12 20:55
What is the common name for the elements in group 7?
Halogens.
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Which two halogens are dangerously reactive?
Fluorine is a dangerously reactive metal. Astatine is radioactive and does not exist in nature.
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What are the two uses of chlorine?
Chlorine is used in the manufacture of bleach and to disinfect drinking water.
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Which block in the periodic table are the halogens in and why?
The halogens are in the P block of the periodic table because the highest occupied subshell is the P subshell.
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What type of molecules do halogens exist as? Give examples.
The halogens exist as diatomic molecules. For example F₂, Cl₂, Br₂ and I₂.
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Give the states of F₂, Cl₂, Br₂ and I₂ at r.t.p.
F₂ = gas, Cl₂ = gas, Br₂ = liquid and I₂ = solid.
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Explain the trend in boiling point down group 7.
As you go down group 7 boiling point increases. As you go down the group the number of electrons increases. The Van der Waals’ forces between molecules get stronger. Therefore boiling point increases and volatility decreases.
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How reactive are the halogens compared to other non-metals?
The halogens are the most reactive of the non-metals.
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What kind of oxidising agents are the halogens and what does this mean?
The halogens are strong oxidising agents (they get reduced).
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What happens when halogens act as oxidising agents? Give an example.
When they act as oxidising agents the halogens are themselves reduced in reactions. E.g. reduction of fluorine to fluoride: F₂ + 2e- = 2F-.
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What is oxidising power?
Oxidising power is a measure of the strength with which an atom is able to attract and capture an electron.
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Explain the trend in reactivity down group 7?
Descending group 7 halogens become less reactive+their oxidising power decreases.This is because descending group 7 the atomic radius and shielding incr.Therefore the ability of an atom to attract and capture an electron to form a halide ion decrease
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What can be used to show the decrease in reactivity down group 7?
Redox reactions can be used to show the decrease in reactivity down group 7. This is shown by halogen displacement reactions of aqueous halides using Cl₂, Br₂ and I₂.
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What happens in a displacement reaction?
In a displacement reaction a more reactive element displaces a less reactive element.
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How are halogen displacement reactions carried out?
Reactions are carried out by adding aqueous solutions of halogens (Cl₂ (aq), Br₂ (aq), I₂ (aq).) to aqueous solutions of the halide ions Cl-(aq), Br-(aq), I-(aq).)
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In a halogen displacement reaction which two halide ions can chloride oxidise?
Chlorine oxidises Br- and I-.
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Write two ionic equations for chlorine oxidising Br- and I-.
Cl₂ + 2Br- = 2Cl- +Br₂and Cl₂ + 2I- = 2Cl- +I₂
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In a halogen displacement reaction which halide ion can bromine oxidise?
Bromine oxidise I- only.
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Write the ionic equation for bromine oxidising I-.
Br₂ + 2I- = 2Br- + I₂
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Can iodine oxides Cl- or Br-?
No because iodine is less reactive (lower down the group in the periodic table) than Cl- and Br-.
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What colour are halide ions in solution?
All halide ions are colourless in solution.
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What solutions do halogens form?
The halogens form aqueous solutions with different colours.
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How is a displacement reaction displayed?
A displacement is indicated by a colour change occurring.
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What colour is bromine in cyclohexane?
Bromine is orange in cyclohexane.
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What colour is iodine in cyclohexane?
Iodine is purple in cyclohexane.
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What colour is chlorine in cyclohexane?
Chlorine is pale green in cyclohexane.
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What is disproportionation?
This is a particular type of redox reaction in which the same element is both oxidise and reduced at the same time.
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Give an example of two disproportionation reactions?
Disproportionation of chlorine in water and disproportionation of chlorine in aqueous sodium hydroxide.
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Why is chlorine added to drinking water?
Small amounts of chlorine are added to drinking water to kill bacteria and make the water safer to drink.
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When chlorine reacts with water what two acids are produced?
HCl and HClO.
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Write the equation for the reaction of chlorine and water. Include state symbols.
Cl₂ (aq) + H₂O (l) = HCl (aq) + HClO (aq).
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What product is formed when dilute aqueous sodium hydroxide and chlorine react?
Diluter aqueous sodium hydroxide and chlorine react together at room temperature to from bleach.
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Write the equation for the formation of bleach. Include state symbols.
Cl₂ (aq) + 2NaOH (aq) = NaCl (aq) + NaClO (aq) + H₂O (l).
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What are the two problems associated with the use of chlorine in drinking water?
Chlorine is a toxic gas – chlorine compounds are toxic and chlorinated hydrocarbons are thought to cause cancer.
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How do you test for halide ions?
Halide ions can be identified using aqueous silver nitrate.Dissolve the halide in water.Add aqueous silver ions using AgNO₃(aq). he silver ions,Ag+(aq), from the AgNO₃(aq) reacts with any halide ions, X- (aq),to form a precipitate of the silver halid
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Write the word equation for the reaction between silver nitrate and (sodium) halide
Silver nitrate + sodium halide = silver halide + sodium nitrate.
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Write the equation for the reaction between silver nitrate and (sodium) halide.
AgNO₃ (aq) + NaX (aq) = AgX (s) + NaNO₃ (aq).
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Write the ionic equation for the reaction between silver nitrate and (sodium) halide.
Ag+ (aq) + X- (aq) = AgX(s).
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Are the silver halides (the products) coloured?
The silver halide precipitates are coloured.
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What does the colour of silver halide precipitates depend on?
The colour depends on which halide is present.
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What do you do if it is difficult to judge the colour of the silver halide precipitates?
It can be difficult to judge the colour so a confirmatory test with aqueous ammonia can be carried out.
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Write the ionic equation for the reaction between silver nitrate and chloride halide. Include state symbols.
Ag+ (aq) + Cl- (aq) = AgCl (s).
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Write the ionic equation for the reaction between silver nitrate and bromide halide. Include state symbols.
Ag+ (aq) + Br- (aq) = AgBr (s)
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Write the ionic equation for the reaction between silver nitrate and iodide halide. Include state symbols.
Ag+ (aq) + I- (aq) = AgI (s).
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What is the colour of the precipitate of a chloride halide in aqueous ammonia?
White.
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What is the colour of the precipitate of a bromide halide in aqueous ammonia?
Cream.
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What is the colour of the precipitate of a iodide halide in aqueous ammonia?
Yellow.
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What is the solubility of chloride in ammonia?
Dilute = yes. Concentrated = yes.
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What is the solubility of bromide in ammonia?
Dilute = no. Concentrated = yes
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What is the solubility of iodide in ammonia?
Dilute = no. Concentrated = no.
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Card 2

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Which two halogens are dangerously reactive?

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Fluorine is a dangerously reactive metal. Astatine is radioactive and does not exist in nature.

Card 3

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What are the two uses of chlorine?

Back

Preview of the front of card 3

Card 4

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Which block in the periodic table are the halogens in and why?

Back

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Card 5

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What type of molecules do halogens exist as? Give examples.

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