Group 7 Flashcards
What does electronegativity mean
Relative tendency of an atom in a molecule to attract a group of elections in a covalent bond
What is the trend in electronegativy in group 7
It decreases because
- as you go down the group the halogens get bigger
- so the atomic radius increases which means the outer electrons are further away from the nucleus
- so there is less attraction
What is the trend in melting and boiling points in group 7
It increases because
- as the molecules get bigger
- more van der waals
- so you need more energy to break the forces
What colour is chlorine in water
Pale green
What colour is bromine in water
Yellow to orange to red
What is the reaction of chlorine with water
Cl2 + H20 -> HCL +HCLO
Or chloric acid can be written as HOCL
What is the use of chloric acid
It is an disinfectant
What is a disproportionation reaction
It is when an element is both reduced and oxidised
Why do we use chlorine to sterilise water even though it’s toxic
The benefit outweighs the costs
What is the reaction to make bleach
Cl2 + 2NAOH -> NaCL + NACLO + H20
What is the reaction of chlorine and water in the presence of sunlight
2CL2 + 2H20 -> 4HCL + O2
What is the trend of oxidation in group 7
It decreases
What would happen if chlorine reacts with potassium bromide
1 say what you would observe
And the ionic equation
Yellow solution would be formed
Cl2 + 2BR- -> 2CL- + Br2
What would happen if chlorine reacts with potassium iodide
1 say what you would observe
And the ionic equation
Brown solution
CL2 + 2I- -> 2CL-+ I2
What would happen if bromine reacts with potassium iodide
1 say what you would observe
And the ionic equation
Br2 + 2I- -> 2BR- + I2
Brown solution
What is the trend of reducing power in group 7
And why?
It increases
Why?
The ions get bigger as you go down the group. Therefore there is less of an attraction to the positive nucleus
So it’s easier to lose electrons
What is the reaction with chloride and concentrated sulphuric acid
Also name the Type of reaction that occurs
NaCL + H2S04 -> NaHSO4 + HCL
Observation
White steamy fumes from HCL- acid base reaction
(Same reaction for fluorine)
What is the reaction with bromide and concentrated sulphuric acid
Include observation and type of reactions
NaBr + H2S04 -> NaHSO4 + HBR
Observation: steamy white fumes
Type of reaction: Acid base
2HBR + H2SO4 -> Br2 + SO2 + 2H20
Observation: orange fumes of bromine and colourless acidic gas
Type of reaction: redox
What is the reaction with iodide and concentrated sulphuric acid
Include observation and type of reactions
NaI + H2S04 -> NaHSO4 + HI
Observation: steamy white fumes
Type of reaction: Acid base
2HI + H2SO4 -> I2 + SO2 + 2H20
Observation: black solid and purple fumes of iodine and colourless acidic gas
Type of reaction: redox
6HI + H2SO4 -> 3 I2 + S + 4H20
Observation: yellow solid of sulphur
Type of equation: redox
8HI + H2SO4 -> 4I2 + H2S + 4H20
Observation: gas with bad egg smell
Type of equation: redox
How would you test for halide ions
You add nitric acid to élimante carbonate ions
And then add Silver nitrate
What happens when you add silver nitrate to a chloride ions
Ag+ + Cl- -> AgCl
White precipitate
What happens when you add silver nitrate to a bromide ions
Ag+ + Br- -> AgBr
Cream precipitate
What happens when you add silver nitrate to a iodide ions
Ag+ + I- -> AgI
Yellow precipitate
If we can’t differentiate between different ions what chemical would you use
Ammonia
What would happen if you add dilute ammonia to chloride ions
Precipitate would dissolve
What would happen if you add dilute ammonia to bromide ions
No visible change
What would happen if you add dilute ammonia to iodide ions
No visible change
What would happen if you add conc ammonia to chlorine ions
Precipitate would dissolve
What would happen if you add conc ammonia to bromine ions
Precipitate would dissolve
What would happen if you add conc ammonia to iodide ions
No visible change
What is the reaction of chlorine of water in uv light
Cl2 + 2H20 -> 4HCL + O2
How would you test for halide ions
You add nitric acid to élimante carbonate ions
And then add Silver nitrate
What happens when you add silver nitrate to a chloride ions
Ag+ + Cl- -> AgCl
White precipitate
What happens when you add silver nitrate to a bromide ions
Ag+ + Br- -> AgBr
Cream precipitate
What happens when you add silver nitrate to a iodide ions
Ag+ + I- -> AgI
Yellow precipitate
If we can’t differentiate between different ions what chemical would you use
Ammonia
What would happen if you add dilute ammonia to chloride ions
Precipitate would dissolve
What would happen if you add dilute ammonia to bromide ions
No visible change
What would happen if you add dilute ammonia to iodide ions
No visible change
What would happen if you add conc ammonia to chloride ions
Precipitate would dissolve
What would happen if you add conc ammonia to bromine ions
Precipitate would dissolve
What would happen if you add conc ammonia to iodide ions
No visible change
What is the reaction of chlorine of water in uv light
Cl2 + 2H20 -> 4HCL + O2
What would happen if you added silver nitrate to fluoride ions
Nothing or no visible change
