(U1) Halogens Flashcards
What colour and state is Fluorine
Yellow gas
what colour and state is Chlorine
Yellow-Green gas
what colour and state is Bromine
Red-Brown liquid
what colour is solid Iodine
Grey-Black
what colour is Iodine vapor
Purple
what colour is Chlorine water
Pale Green/Colourless
what colour is Bromine water
Brown
what colour is Iodine in POLAR solvents
Yellow-Brown
what colour is Iodine in NON-POLAR Solvents
Purple
What is the observation for reactions between:
- Fluorides and
- Concentrated Sulfuric Acid
(Not needed as much)
Steamy/Misty Fumes (of HF)
What is the observation for reactions between:
- Chlorides and
- Concentrated Sulfuric Acid
Steamy/Misty Fumes (of HCI)
What are the observations for reactions between:
- bromides and
- Concentrated Sulfuric Acid
(3)
- Steamy/Misty Fumes (HBr)
- Red-Brown Vapour (Br2)
- pungent smell (SO2)
What are the observations for reactions between:
- Iodides and
- Concentrated Sulfuric Acid
(7)
3 reactions:
1.
- Steamy/misty fumes (of HI)
- Purple Vapour (I2)
- pungent smell (SO2)
- Yellow solid (S)
- Smell of Rotten Eggs (H2S)
- Grey-Black solid (on the sides of the test tube) (I2)
What is the observation for reactions between:
- solid fluorides and
- Concentrated phosphoric Acid
Steamy/misty fumes (of HF)
What is the observation for reactions between:
- Chlorides and
- Concentrated phosphoric Acid
Steamy/misty fumes (of HCI)
What is the observation for reactions between:
- Bromides and
- Concentrated phosphoric Acid
Steamy/misty fumes (of HBr)
What is the observation for reactions between:
- Iodides and
- Concentrated phosphoric Acid
Steamy/misty fumes (of HI)
State every reaction between sodium iodide and sulphuric acid in order
- NaI + H2SO4 —> HI + NaHSO4
- HI + H2SO4 —> SO2 + I2 + 2H2O
- 6HI + H2SO4 —> S + I2 + 4H2O
- HI + H2SO4 —> H2S + I2 + H2O
Last 2 reactions occur because iodide ions are greater reducing agents than halides up the group
What happens to the oxidising ability of halogens down the group?
Oxidising ability decreases
What happens to the reducing ability of halides down the group?
Reducing ability increases
Why are halide ions reducing agents while atoms are oxidising agents? (3)
- ions lose electrons more readily
- larger atomic radius + greater shielding make this easier
- also halogen atoms would rather gain electrons than lose (oxidising agents), ions are stable
Why are the halogens more soluble in non-aqueous / non polar solvents than in aqueous / polar solvents?
like dissolves like
- halogen molecules and non-polar solvents are both held by Van der Waals forces
- as a result little energy is required to disrupt the forces and form a solution
- aqueous solutions contain both Van der Waals and hydrogen bonds —> requires more energy to disrupt
Why are the halogens soluble in aqueous / polar solvents?
Purely because polar solvents are polar and halogens are non-polar —> opposites attract
What colour is Chlorine in non-polar solvents?
Pale green - but not colourless
What colour is Bromine in non-polar solvents?
Brown
Give the balanced symbol equation for the reaction between water and chlorine
Give state symbols
Then give the word equation
- Cl2 (g) + H2O(l) —> HCl(aq) + HClO(aq)
- chlorine + water —> hydrochloric acid + chloric (I) acid (or chlorine water)
Give the balanced symbol equation for the reaction between chlorine and cold dilute NaOH
Include state symbols
Then give the ionic equation
- Cl2 (g) + 2NaOH(aq) —> NaCl(aq) + NaClO(aq) + H2O(l)
- Cl2 (g) + 2OH-(aq) —> Cl-(aq) + ClO-(aq) + H2O (l)
Give the balanced symbol equation for the reaction between chlorine and hot (70ºC) concentrated NaOH
Include state symbols
Then give the ionic equation
- 3Cl2 (g) + 6NaOH(aq) —> 5NaCl(aq) + NaClO3 (aq) + 3H2O(l)
- 3Cl2 (g) + 6OH-(aq) —> 5Cl-(aq) + ClO-3 (aq) + 3H2O (l)
What does and Iodate ion (IO-) disproportionate to produce?
Iodide (I-) and Iodate (v) (IO4-) ions
Why is chlorine added to drinking water?
Kills pathogens and prevents spread of disease
Why is ozone added to drinking water?
Breaks down parasites along with pathogens
What are the advantages and disadvantages of using chlorine in drinking water?
Give 2 of each.
Advantages:
- Chlorine is a highly efficient disinfectant
- Residual chlorine remains in the water —> controls contamination
- Easy to produce and relatively cheap.
- Chlorine gas can be compressed.
Disadvantages:
- Chlorine is poisonous/toxic.
- Can’t treat all water-borne pathogens while ozone can
- can react to produce compounds known as disinfection by-products (DBP) which can cause health hazards such as cancer.
- volatile and not all of it remains dissolved in the water.
- Can spoil the taste of the water.
- Chlorine can affect the odour/smell of the water.
- Storing large quantities of chlorine causes problems.
- inhibits freedom of choice
What are the advantages and disadvantages of using ozone in drinking water?
Give 2 of each.
Advantages:
- Cost effective
- Greater disinfection effectiveness against bacteria and viruses than chlorination.
- Has oxidising properties —> lowers the concentration of metals such as iron and manganese by converting them into insoluble metal oxides that can be removed by filtration.
- Can treat all water-borne pathogens.
Disadvantages:
- Unstable —> no residual ozone left in the water to control contamination
- does not remove nitrates or chlorides
- does not remove hardness from the water
- inhibits freedom of choice
