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Chemistry Module 3 > Group 7 > Flashcards

Group 7 Flashcards

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1
Q

List 2 properties of halogens?

A
  • Low melting and boiling points
  • Exist as diatomic molecules
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2
Q

What is the trend in reactivity down group 7?

A

Reactivity decreases because atomic radius and electron shielding increases so the ability to gain an electron decreases.

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3
Q

What is the trend in oxidising ability down the group?

A

Decreases down the group (Cl strongest and I the weakest), because Cl has the fewest occupied shells it has the greatest attraction between outer electrons and nucleus thus easier to gain electrons

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4
Q

What is the trend in reducing ability down the group?

A

Decreases down the group (Cl weakest I strongest) because outer electrons are furthest from the nucleus, weaker force of attraction thus easiest to be oxidised

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5
Q

When a more reactive halogen displaces a less reactive halide, what is this reaction called?

A

Displacement reaction

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6
Q

What is the colour of chlorine in water?

A

Pale green

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7
Q

What is the colour of bromine in water?

A

Orange

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8
Q

What is the colour of iodine?

A

Brown

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9
Q

What is the colour of chlorine in cylohexane?

A

Pale green

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10
Q

What is the colour of bromine in cylohexane?

A

Orange

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11
Q

What is the colour of bromine in cylohexane?

A

Orange

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12
Q

What is the colour of iodine in cylohexane?

A

Violet

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13
Q

Out of the 3 halide ions which one can be oxidised by chlorine?

A

Br- and I- ions

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14
Q

Write the equation for chlorine displacing bromide ions?

A

Cl2 + 2Br -> 2Cl- + Br2

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15
Q

Write the equation for Cl2 oxidising 2I-.

A

Cl2 + 2I- -> 2Cl- + I2

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16
Q

Out of the 3 halides which one can be oxidised by bromine?

A

I- ions

17
Q

Write the equation for bromine displacing iodide ions.

A

Br2 + 2I- -> 2Br- + I2

18
Q

Define disproportionation

A

The oxidation and reduction of the same element in a redox reaction

19
Q

What is the equation for the reaction of Cl2 with water?

A

Cl2 + H2O -> HClO + HCL

20
Q

What type of reaction is the reaction of chlorine with water?

A

Disproportionation, chlorine is both oxidised and reduced

21
Q

What acts as a weak bleach in this reaction?

A

HClO (chloric acid)

22
Q

What kills the bacteria in this reaction?

A

ClO- (chlorate ions) and chloric acid

23
Q

Is chlorine soluble in water?

A

Insoluble in water but can dissolve in sodium hydroxide

24
Q

How do you test for carbonates?

A
  • Add dilute acid to a solution containing carbonate ions
  • Will cause fizzing/effervescence due to the production of CO2 (limewater confirms the production of CO2)
25
Q

How do you test for sulphates?

A
  • Firstly add dilute HCl to remove any impurities (carbonates)
  • Add barium chloride which contains barium ions and a white precipitate should form
26
Q

How do you test for halides?

A
  • Firstly add dilute nitric acid to get rid of any impurities (carbonates or sulfite)
  • Add silver nitrate to form a precipitate
27
Q

What colour are the precipitates for each halide ion?

A

Cl- is a white precipitate
Br- is a cream precipitate
I- is a yellow precipitate

28
Q

Why is it important to carry out the carbonate test before the sulfate test?

A

If you carry out a sulfate test on a carbonate you will get a white precipitate too, only proceed to the sulfate test once you know there is no carbonate present

29
Q

What are the products formed when chlorine reacts with sodium hydroxide?

A

NaClO, NaCl and H2O

30
Q

How do you test for ammonium compounds?

A
  • Add sodium hydroxide
  • Gently heat and gas will be produced
  • Use damp red litmus paper should turn blue
31
Q

What is the equation for another disproportionate reaction that is found in household bleach?

A

Cl2 + NaOH -> NaClO + NaCl + H2O

32
Q

Explain why, if you are testing a mixture, it is important to use dilute nitric acid instead of sulfuric and hydrochloric acid, for the carbonate test?

A

If sulfuric acid is used, sulfate ions will show up in the sulfate test with Ba2+ and if HCl is used chloride ions will show up in the halide test with Ag+

33
Q

Explain why group 7 has an increase in boiling point down the group

A
  • Has van der Waals’ forces
  • As you go down the group the number of electrons increase so the energy needed to break these forces increases
34
Q

At stage 1 the student bubbled some chlorine through an aqueous solution of potassium iodide. What would the student see at stage 1?

A

Goes brown

35
Q

Halogens have van der Waals’ forces between their molecules.
(i) Describe how van der Waals’ forces arise.

A
  • Uneven distribution of electrons
  • Creates an instantaneous dipole
  • Causes an induced dipole in neighbouring molecules

Chemistry Module 3 (5 decks)

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