The Halogens

Question 1

what is the colour and state of fluorine in its physical state ?

Answer 1

pale yellow GAS

Question 2

what is the colour and state of chlorine in its physical state ?

Answer 2

green GAS

Question 3

what is the colour and state of bromine in its physical state ?

Answer 3

red-brown liquid

Question 4

what is the colour and state of iodine in its physical state ?

Answer 4

black solid

Question 5

describe the trend in boiling points down the halogens (4)

Answer 5

• boiling point increases down group
• number of electrons increases
• greater IDDI between mlcls
• more energy needed to overcome IDDI

Question 6

describe the trend in reactivity down group 7 (6)

Answer 6

• reactivity decreases down group
• more electron shells
• greater electron shielding
• greater atomic radius
• weaker nuclear attraction between nucleus and outermost electron
• attracts an electron to form an anion less readily

Question 7

which halogen is the most reactive ?

Answer 7

fluorine

Question 8

which halogen has the greatest boiling point out of fluorine, chlorine, bromine or iodine

Answer 8

iodine

Question 9

which halogen acts as the best oxidising agent ?

Answer 9

fluorine

Question 10

write an ionic equation for the displacmentreaction which occurs when bromine reacts with sodium iodide

Answer 10

Br2 (aq) + 2I- (aq) = 2Br- (aq) + I2 (aq)

Question 11

describe what is found in the organic and aqueous layer which results after a displacment reaction (2)

Answer 11

• non polar halogen wil disolve in non polar organic layer
• polar halide will disolve in polar aqueous layer

Question 12

give an example of an aqueous and organic solvents that can be used for the displacement reaction between halides and halogens

Answer 12

organic: hexane
aqueous: water

Question 13

what is the colour of Cl2 when it is dissolved in water - Cl2 (aq)

Answer 13

pale green

Question 14

what is the colour of Br2 when it is dissolved in water- Br2 (aq)

Answer 14

orange

Question 15

what is the colour of I2 when it is dissolved in water - I2(aq)

Answer 15

brown

Question 16

what is the colour of Cl2 when it dissolves in the organic solvent: hexane

Answer 16

pale yellow - green

Question 17

what is the colour of Br2 when it dissolves in the organic solvent: hexane

Answer 17

yellow-orange

Question 18

what is the colour of I2 when it dissolves in the organic solvent: hexane

Answer 18

purple

Question 19

describe the method used for a diaplacement reaction (3)

Answer 19

• use seperating funnel
• shake hexane with dilute aqueous halide solution
• aqueous and organic layer form - organic on top

Question 20

describe a p[ractical use of chlorine (1)

Answer 20

sterilise water by killing bacteria

Question 21

describe the process of chlorination of water include any relevent equations (4)

Answer 21

**step 1: **
Cl2 (aq) + H2O (l) = HCL (aq) + HClO (aq)
chloric acid formed - kills bacteria

**step 2: **
HClO (aq) = H+ (aq) + ClO- (aq)
chlorate(I) formed - sterilising agent

Question 22

what would the observations be if universal indicator was added to the firat step of water chlorination ? (2)

Answer 22

• first it would trun red - due to acidic product (HCl)
• then turns colourless - HClO bleaches colcour

Question 23

state some advantages of using chlorine to sterilise water and kill bacteria (3)

Answer 23

• highly effective at killing bacteria
• simple maintenance
• not expensive

Question 24

state some disadvantages of using chlorine to sterilise water and kill bacteria (3)

Answer 24

• chlorine is toxic
• forms halogenated hydrocarbons
• forms carcinogenic cmpnds