State of bromine
Red/ brown liquid
State of iodine
Black solid
Cl2 when in
water
cyclohexane
Pale green
Br2 when in
Water
Cyclohexane
Orange
I2 when in
Water
Cyclohexane
Brown
Purple
Purpose of chlorine in water purification
Kills pathogen to avoid disease
Chlorine reacts with water to form acidic solution that kills pathogens
Chlorine and water reaction
Forms
hydrochloric acid
Chloric acid (HOCl)
Why is Cl2 reaction with H2O disproportionation reaction
Chlorine is both oxidised and reduced
Oxidised on HOCl
Reduced in HCl
Risks of using chlorine to purify water
Gas is toxic
Chlorinated hydrocarbon may form which are carcinogenic
Benefits of Chlorine purifying water
Kills many harmful microorganisms
Reduces rates of waterborne disease; cholera and typhoid
How is bleach created
Cl2 and cold dilute NaOH
Forms NaOCl and NaCl
NaOCl is the bleach
State and colour of chlorine
Yellow/ green gas
Describe trend in boiling point down the group.
- Increases
- Greater amount of electrons down the group means that there are stronger London forces between the molecules
- Thus requiring greater energy to break the attraction
Describe the test for halide ions.
Including ionic equation.
- Add AgNO3 to unknown solution
- Precipitation reaction will form a Silver halide
- X- + Ag+ = AgX
- Colour of the ppt indicates the type of halide ion;
White- Chloride
Cream- Bromide
Yellow- Iodide
The further distinguish, NH3 is added;
Dilute NH3 dissolves Cl- but not Br-
Concentrated NH3 dissolves Br-
