The Halogens

Question 1

Physical properties of halogens

Answer 1

Most reactive non metallic group

Found as stable halide ions, dissolved in sea water, combined as solid deposits with sodium

Question 2

Trends in boiling point

Answer 2

RTP, diatomic molecules

Increase in boiling point die to more electrons, stronger London forces, more energy needed to break LF, increase BP

Question 3

Halogen colours

Answer 3

F2, pale yellow
Cl2, pale green gas
Br2, red brown liquid
I2, shiny grey black solid
At2, never seen

Question 4

Redox reactions

Answer 4

Halogen atom reduced, gains one electron to form 1- halide with config of nearest noble gas
Oxidising agent gets reduced

Question 5

Halogen halide displacement reaction

Answer 5

Shows reactivity of halogens decrease down group
Halogen displaces halide from solution, colour change if halogen more reactive
Add cyclohexane to make colours more vivid
Colour present shows displaced halogen
Oxidation number changes

Question 6

Results of halogen halide displacement reaction

Answer 6

Chlorine reacted with Br-, I-
Bromine reacted with I-
Iodine has not reacted

Question 7

Reactivity of fluorine, astatine

Answer 7

Fluorine reacts with almost any substance that it come in contact with
Astatine has never been seen, least reactive

Question 8

Trends in reactivity

Answer 8

Redox reactions, halogens react by gaining e-
Down group, atomic radius increases, more inner shells so shielding increases, less nuclear attraction to capture an electron from another species, reactivity decreases
Become weaker oxidising agents down group

Question 9

Disproportionation

Answer 9

Redox reaction in which same element is oxidised and reduced

Question 10

Reaction of chlorine with water

Answer 10

Chlorine used in water purification
Chloric (I) acid is a weak bleach
Add indicator to chlorine and water solution
Initially goes red, then bleaches

Cl2(aq) + H2O(l) => HClO(aq) + HCl(aq)

Question 11

Reaction of chlorine with cold sodium hydroxide

Answer 11

Cl2(aq) + 2NaOH(aq) => NaClO(aq) + NaCl(aq) + H2O(l)

Resulting solution has large concentration of chlorate (I) ions from NaClO
Solution is a household bleach

Question 12

Benefits of chlorine

Answer 12

Beneficial in asking water os drinkable after natural disasters, prevent typhoid, cholera

Question 13

Risks of chlorine

Answer 13

Extremely toxic
Respiratory irritant
If reacted with organic hydrocarbons, chlorinated hydrocarbons formed, cause cancer