3: Group 7 Flashcards
What colour is flourine?
Yellow
What colour is chlorine?
Green
What colour is bromine?
Red-brown
What colour is iodine?
Grey
What state is chlorine and fluorine at room temperature?
Gas
What state is bromine at room temperature?
Liquid
What state is iodine at room temperature?
Solid
How does boiling point change down group 7 and why?
Increases. This is due to larger van der waals forces as atoms get larger.
Why do halogens act as oxidising agents?
They gain an electron, so they become reduced and oxidise other things.
How does electronegativity change down group 7?
Decreases because atoms get larger, so electrons are further from the nucleus. This means there is less attraction.
How does oxidising power change down group 7?
Oxidising power decreases. This is because the outer electron shell gets further from the nucleus.
What will be observed in a reaction with KBr and Cl2?
Orange solution as Br2 is formed.
What will be observed in a reaction with KI and Cl2?
Brown solution formed as I2 is produced
What will be observed in a reaction with KI and Br2?
Brown solution formed as I2 is produced
What is a disproportionation reaction?
Where the same molecule is oxidised and reduced in the same reactions
Give an equation for the formation of bleach with state symbols.
2NaOH (aq) + Cl2 (g) -> NaClO (aq) + NaCl (aq) + H2O (l)
What is the chemical formula of bleach?
NaClO
Give the redox equation for chlorine + H2O with state symbols.
Cl2 (g) + H2O (l) = 2H+ (aq) + Cl- (aq) + ClO- (aq)
Give the redox equation for chlorine and water in sunlight. Include state symbols.
Cl2 (g) + H2O (l) = 2H+ + 2Cl- + 0.5O2
What are chlorate ions used for?
To kill bacteria. It can be put in water which makes it safe to drink.
What is the disadvantage of water being used to kill drinking/swimming water?
Toxic
Chlorine can be used to prevent the growth of which photosynthetic organism in water?
Algae
What are the side effects of using chlorine in water?
Causes respiratory issues, irritates eyes and skin
How does reducing power of halides change down the group and why?
Increases. This is because outer electrons get further from the nucleus and attraction gets weaker. This means its easier to lose an electron and donate it elsewhere (to reduce the other species).
Give the equations for the reaction of NaF/NaCl with H2SO4 with state symbols.
NaF (s) + H2SO4 (aq) -> NaHSO4 (s) + HF (g)
NaCl (s) + H2SO4 (aq) -> NaHSO4 (s) + HCl (g)
What observations could you make from NaF/NaCl + H2SO4?
White misty fumes.
Why is there only one stage to the reactions of NaF/NaCl with H2SO4?
They are not powerful enough reducing agents
Give the equation for NaBr + H2SO4 including state symbols.
Give the equation when one of the products of this reaction reacts with more H2SO4.
NaBr (s) + H2SO4 (aq) -> NaHSO4 (s) + HBr (g)
2HBr (aq) + H2SO4 -> Br2 (g) + SO2 (g) + 2H2O (l)
What observations could you make from the reaction of NaBr and H2SO4?
Choking fumes of SO2 produced.
Orange fumes of Br2 produced.
Why are there 2 stages to the reaction of H2SO4 and HBr?
Bromide ions are stronger reducing agents.
Give the 3 stages of the reaction of NaI and H2SO4.
NaI (s) + H2SO4 (aq) -> NaHSO4 (s) + HI (g)
2HI (aq) + H2SO4 (aq) -> I2 (g) + SO2 (g) + 2H2O (l)
6HI + SO2 (aq) -> H2S (g) + 3I2 (s) + 2H2O (l)
What observations can you make from the reaction of NaI and H2SO4?
H2S fumes, which smells of rotten eggs and solid iodine.
