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CHEMISTRY > Group 7 > Flashcards

Group 7 Flashcards

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1
Q

How do group 7 elements exist?

A

As diatomic molecules

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2
Q

How many electrons do group 7 elements have in their p orbitals?

A

nP5

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3
Q

Trend in boiling point down the group

A

Increases

  • increased London forces due to more electrons
  • more energy required to separate the molecules
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4
Q

Physical state of Chlorine at room temperature

A

Gas (green)

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5
Q

Physical state of Bromine at room temperature

A

Liquid (red-brown)

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6
Q

Physical state of Iodine at room temperature

A

Solid (grey/black)

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7
Q

Trend in electronegativity going down the group

A

Decreases down the group

  • increased distance from nucleus
  • more shielding

These two factors cancel out the effect of increased nuclear charge

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8
Q

Trend in atomic radius going down group 7

A

Increases

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9
Q

Trend in ionic size going down the group

How does this compare with the size of the atoms of the elements?

A

Increases

Ions are larger due to increased number of electrons
This means the force of attraction from the nucleus is spread more thinly so electrons move further out

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10
Q

Trend in oxidising ability going down the group

Explain the trend

A

Decreases

  • less attraction from the nucleus due to increased distance
  • more shielding
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11
Q

Which halogen out of Cl, Br and I is best at displacing other halogens?

Give the order of displacement

A

Cl

Cl > Br > I

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12
Q

Give the equation for the oxidation of bromide ions using chlorine

A

Cl2 + 2Br- –> Br2 + 2Cl-

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13
Q

Give the equation of bromine oxidising Iodide ions to iodine

A

Br2 + 2I- –> I2 + 2Br-

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14
Q

Give the equation for the reaction of chlorine with sodium bromide

A

Cl2 + 2NaBr –> 2NaCl + Br2

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15
Q

Give the equation for the reaction of chlorine with water and the results of testing the reaction with litmus paper

A

Cl2(g) + H20(l) ⇌ HCl(aq) + HOCl(aq)

Litmus would turn red, due to the HCl, and then be bleached white by the HOCl

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16
Q

Give a use of NaClO

A

Active ingredient in household bleach

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17
Q

Equation for the reaction of chlorine with cool, dilute aqueous sodium hydroxide

What type of reaction is it?

A

Cl2 + 2NaOH –> NaCl + NaClO +H2O

Disproportionation as the chlorine is both oxidised and reduced

18
Q

Give another name for sodium chlorate(I)

A

Sodium hypochlorite

19
Q

Give the equation of the reaction between chlorine with hot, concentrated sodium hydroxide solution

A

3Cl2 + 6NaOH –> 5NaCl + NaClO3 + 3H2O

20
Q

What is the name of NaClO3?

A

Sodium chlorate(V)

21
Q

Which halide ion is the most reducing?

Why?

A

I-

-as ionic radius increases, it becomes easier to remove outer electrons

22
Q

Describe the test for halides using silver nitrate

A
  • Add dilute nitric acid to the sample containing the halide
  • Add a few drops of silver nitrate solution
  • Observe colour of precipitate of silver halide
23
Q

Describe what you would do to precipitates formed from adding silver nitrate to solutions containing halides. Give the results

A
  • Add dilute ammonia solution
  • If precipitate still exists, add concentrated ammonia solution

Silver chloride - dissolves in both dilute and concentrated ammonia solution

Silver bromide - dissolves in concentrated ammonia solution but not in dilute

Silver Iodide - doesn’t dissolve in either

24
Q

Give the colours of the precipitates formed from the three halides reacting with silver nitrate solution

A

Chloride - White ppt

Bromide - Cream ppt

Iodide - Yellow ppt

25
Q

What is the complex formed when a silver halide is dissolved in ammonia?

A

[Ag(NH3)2]+

Colourless diammine complex

26
Q

Write the equation for the partial ionisation of sulfuric acid

A

H2SO4 ⇌ H+ + SO4 2-

27
Q

Three possible reduction products of sulfuric acid

A

Sulfur dioxide - SO2

Sulfur - S

Hydrogen sulfide - H2S

28
Q

What happens when you add concentrated sulfuric acid to the halides?

A
  • Sulfuric acid displaces the weaker acids HCl, HBr and HI from their salts
  • Hydrogen halides all fume in moist air
  • Sulfuric acid is reduced to lower oxidation states of Sulfur the further you go down the group
29
Q

What are the products when concentrated sulfuric acid is added to a solution of NaCl?
Give the equation and any observations

A

HCl produced

White, misty fumes given off

NaHSO4 also produced

NaCl + H2SO4 –> NaHSO4 + HCl

30
Q

Give the products, equations and observations for when concentrated sulfuric acid is added to NaBr

A

NaBr + H2SO4 –> NaHSO4 + HBr

The HBr then goes on to react with the sulfuric acid:

2HBr + H2SO4 –> 2H2O + SO2 + Br2

HBr - misty fumes

Br2 - brown fumes

SO2 - Colourless gas with a choking smell

31
Q

What are the two half equations for the reaction of NaBr and H2SO4?

A

2Br- –> Br2 + 2e-

H2SO4 + 2H+ + 2e- –> 2H2O + SO2

32
Q

Give the products, equations and observations for the reaction of NaI and H2SO4

A

NaI + H2SO4 –> NaHSO4 + HI

Hydrogen iodide goes on to react with H2SO4:

6HI + H2SO4 –> 4H2O + S + 3I2

Sulfuric acid is reduced to hydrogen sulfide:

H2SO4 + 8e- + 8H+ –> H2S + 4H2O

Observations:

HI - misty fumes

I2 - purple fumes or black solid

SO2 - colourless gas with choking smell

S - yellow solid

H2S - colourless gas with rotten egg smell

33
Q

What is the trend in temperature of the hydrogen halides?

A

HF > HCl > HBr > HI

34
Q

How does reducing ability of the hydrogen halides change as you go down the group?

A

Increases

-due to bond strength decreasing

35
Q

Uses of chlorine

A
  • Water purifier
  • bleach
  • solvents
  • CFC’s
36
Q

Equation of HBr reacting with water

A

HBr + H2O –> H3O+ + Br-

Forms hydrobromic acid and bromide ions

37
Q

Give the equation for the reaction between hydrogen chloride and water

A

HCl + H20 –> H3O+ + Cl-

Forms hydrochloric acid

38
Q

Give the equation for the reaction between HI and H2O

A

HI + H20 –> H3O+ + I-

39
Q

Products of hydrogen halides reacting with ammonia.

Give an example

A

Form salts which are white ionic solids

40
Q

Give the equation for the reaction between hydrogen chloride gas and ammonia gas

A

NH3(g) + HCl(g) –> NH4Cl(s)

41
Q

What is special about fluoride ions when you add silver nitrate to them?

A

They don’t form a silver halide precipitate

CHEMISTRY (18 decks)

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