U2S2 group 7

Question 1

What are the main properties of the first four halogens

Answer 1

• flourine, pale yellow, gas
• chlorine, green, gas
• bromine, red-brown, liquid
• iodine, grey, solid

Question 2

What happens to boiling points as go down group

Answer 2

• increase
• larger molecules so van der waals forces increase

Question 3

What happens to electronegativity as go down group

Answer 3

• decreases
• larger atoms so weaker attraction of nucleus and electrons

Question 4

What happens to oxidising strength as go down group

Answer 4

Decreases

Question 5

What happens when chlorine reacts with KBr and KI

Answer 5

• KBr, orange solution of Br2 formed
• KI, brown solution of I2 formed

Question 6

What happens when bromine reacts with KI

Answer 6

Brown solution of I2 formed

Question 7

How do you make bleach

Answer 7

• mix chlorine has with cold, dilute sodium hydroxide at room temperature
• produces sodium chlorate
• disproportionation as chlorine oxidised and reduced at same time
• 2NaOH(aq) + Cl2(g) -> NaClO(aq) + NaCl(aq) + H2O(l)

Question 8

How does chlorine react with water

Answer 8

• when mix, undergoes disproportionation
• Cl2(g) + H2O(l) -> 2H+(aq) + Cl-(aq) + ClO-(aq)
• in sunglight, chlorine can decompose water to form chloride ions and oxygen
• Cl2(g) + H2O(l) -> 2H+(aq) + 2Cl-(aq) + 1/2O2(g)