Group 7 Flashcards
What are the characteristics of fluorine?
Colour- pale yellow
Physical state- gas
highly reactive
What are the characteristics of chlorine?
Colour- green
Physical state - gas
poisonous in high concentrations
What are the characteristics of bromine?
Colour- red-brown
Physical state- liquid
produces dense brown/orange poisonous fumes
What are the characteristics of iodine?
Colour- grey
Physical state-solid
produces purple gas
What is the trend of boiling points down the group?
The boiling points increase
Why do the boiling points increase down the group?
Down the group, the molecules are larger
There are more electrons
Therefore, there are stronger van der Waals forces
More energy is required to break the forces
What is the trend of electronegativity up the group?
The electronegativity increases
Why does the electronegativity increase up the group?
The atomic radius decreases
there is less shielding
there is a stronger force of attraction on the electrons
What is electronegativity?
The relative tendency of an atom in a molecule to attract electrons in a covalent bond to itself
Why is fluorine the most electronegative element?
It is the smallest atom with the most need to fill its shell
it has the least number of electrons and shells
What happens when a halogen reacts with a halide in a solution?
A halogen will displace a halide from the solution if the halide is below the halogen in the periodic table
What is the trend of oxidising strength down the group?
The oxidising strength decreases down the group
What happens when potassium chloride reacts with chlorine?
No reaction
Remains green
What happens when potassium chloride reacts with bromine?
No reaction
Remains orange
What happens when potassium chloride reacts with iodine?
No reaction
Remains brown
What happens when potassium bromide reacts with chlorine?
Orange solution formed
Chlorine has been displaced by bromine
What happens when potassium bromide reacts with bromine?
No reaction
Remains orange
What happens when potassium bromide reacts with iodine?
No reaction
Remains brown
What happens when potassium iodide reacts with chlorine?
Brown solution formed
Chlorine displaced by iodine
What happens when potassium iodide reacts with bromine?
Brown solution formed
Bromine displaced by iodine
What happens when potassium iodide reacts with iodine?
No reaction
What is the trend of the reducing power of the halides down the group?
The reducing power increases down the group
Why does the reducing power increase down the group?
- the ions get bigger down the group
- the further away the outer electrons are from the nucleus
- there is more shielding
- weaker force of attraction
What happens when the reducing power increases down the group?
The greater the reducing power
the greater the reactivity
the faster the reduction reactions take place
What happens when fluoride reacts with concentrated sulfuric acid?
NaF(s) + H2SO4(aq) → NaHSO4(s) + HF(g)
What happens when chloride reacts with concentrated sulfuric acid?
NaCl(s) + H2SO4(aq) → NaHSO4(s) + HCl(g)
Why are the reactions between fluoride and chloride with concentrated sulfuric acid not redox reactions?
HF and HCl aren’t strong enough reducing agents to reduce the sulfuric acid
The oxidation states of the halide and sulfur remain the same
What happens when bromide reacts with concentrated sulfuric acid?
NaBr(s) + H2SO4(aq) → NaHSO4(s) + HBr(g)
2HBr(aq) + H2SO4(aq) → Br2(g) + SO2(g) + 2H2O(l)
What happens when iodide reacts with concentrated sulfuric acid?
NaI(s) + H2SO4(aq) → NaHSO4(s) + HI(g)
2HI(g) + H2SO4(aq) → I2(s) + SO2(g) + 2H2O(l)
6HI(g) + SO2(aq) → 3I2(s) + H2S(g) + 2H2O(l)
What observations can be made when bromide reacts with concentrated sulfuric acid?
steamy fumes of HBr are produced
Red fumes of Br2
colourless, acidic gas, SO2
What observations can be made when iodide reacts with concentrated sulfuric acid?
steamy fumes of HI are produced black solid and purple fumes of I2 colourless acidic gas, SO2 yellow solid, sulfur toxic, rotten egg smell, H2S
What observations can be made when iodide reacts with concentrated sulfuric acid?
steamy fumes of HI are produced black solid and purple fumes of I2 colourless acidic gas, SO2 yellow solid, sulfur toxic, rotten egg smell, H2S
How would you test for halides using silver nitrate
Add nitric acid to the solution to remove ions which may give a false positive result
Add a few drops of silver nitrate solution
A precipitate is formed
The colour of the precipitate will determine the halide present
What is the colour of the precipitate when silver nitrate is used to test chlorides?
White precipitate
What is the colour of the precipitate when silver nitrate is used to test bromides?
Cream precipitate
What is the colour of the precipitate when silver nitrate is used to test iodides?
Yellow precipitate
What is the trend of solubility of silver halides in ammonia?
The solubility decreases down the group
What observations would be made when ammonia is added to silver chloride?
White precipitate
Silver chloride dissolves in dilute ammonia
What observations would be made when ammonia is added to silver bromide?
Cream precipitate
Silver bromide dissolves in concentrated ammonia
What observations would be made when ammonia is added to silver iodide?
Yellow precipitate
Insoluble in both dilute and concentrated ammonia
Why is chlorine used in water?
It kills bacteria
What happens when chlorine reacts with water?
It undergoes disproportionation
What is disproportionation?
A reaction where an is element simultaneously oxidised and reduced
What happens when chlorine reacts with water?
Cl2(g) + H2O(l) → 2H+(aq) + Cl-(aq) + ClO(aq)
What happens when chlorine reacts with water in sunlight?
2Cl2(g) + 2H2O(l) → 4H+(aq) + 4Cl-(aq) + O2(g)
What are the disadvantages of using chlorine for water treatment?
- chlorine gas is harmful
- liquid chlorine causes severe burns
- chlorine reacts with organic compounds in water forming chlorinated hydrocarbons which are carcinogenic
Why is chlorine still used in water treatment?
The benefits to health of water treatment by chlorine outweighs its toxic effects
What happens chlorine reacts with cold, dilute aqueous NaOH?
2NaOH(aq) + Cl2(g) → NaClO(aq) + NaCl(aq) + H2O(l)
What is sodium chlorate(NaClO) used for?
bleach
