Group 7 Flashcards
State and appearance of halogens at room temperature
Fluorine: yellow gas
Chlorine: green gas
Bromine: orange/brown liquid
Iodine: dark grey solid
Colour of vapour for halogens
Bromine: orange
Iodine: purple
Colour in polar solvent for halogens
Chlorine: very pale green to colourless
Bromine: orange bromine water
Iodine: brown iodine solution
Colour in non-polar solvents
Chlorine: green
Bromine: orange
Iodine: violet
Describe the trend in atomic radius down group 7
It increases
Explain the change in atomic radius down group 7
More electrons, so more shells, so distance between nucleus and outer shell is greater
Describe the trend in electronegativity down group 7
It decreases
Explain the trend in electronegativity in group 7
More shells, more shielding, and bigger atomic radius - so weaker attraction between nucleus and outer shell electron
Describe the trend in ionisation enthalpy in group 7
It decreases: More shells, more shielding, and bigger atomic radius - so weaker attraction between nucleus and outer shell electron
Describe the trend in melting/boiling point down group 7
It increases
Explain the trend in melting/boiling points down group 7
There are more electrons, so stronger Van der Waals’ forces between molecules which require more energy to overcome.
Why is Chlorine added to water?
It kills bacteria at low levels. (Toxic at high levels!! ARGH!)
What is produced in the reaction between Chlorine and water?
Hydrochloric acid and Chloric (I) acid
What is the balanced equation for the reaction between Chlorine and water in the dark?
What type of reaction is this?
Cl2 (aq) + H2O (l) HCl (aq) + HClO (aq)
Redox disproportionation reaction
What is the balanced equation for the reaction between Chlorine and water in the light?
2Cl2(aq) + 2H2O(l) –> 4HCl(aq) + O2(g)
What is the balanced equation for the reaction between chlorine and sodium hydroxide?
What is the product commonly known as?
Cl2(aq) + 2NaOH(aq) –> NaCl(aq) + NaClO(aq) + H2O(l)
Bleach (the aqueous mixture of the products)
What is an oxidising agent?
An element that is itself reduced so causes other elements to be oxidised.
Describe the trend in reactivity down the group.
It decreases down the group
Explain the trend in reactivity down the group.
Atomic radius increases, shielding increases - so the electrostatic attraction between the nucleus and the electron to be gained decreases
What colour are halide ions?
colourless
What is a reducing agent?
A substance that is itself oxidised so causes the other substance to be reduced.
What is the best to worst halide reducing agent?
Iodide (can reduce H2SO4 to SO2, S and H2S)
Bromide (can reduce H2SO4 only to SO2)
Chloride (cannot reduce H2SO4)
What observations are there for all potential products when H2SO4 is reduced?
SO2 is a colourless gas
S is a yellow solid
H2S is a colourless gas with a bad egg smell
What are the observations for a halide acid-base reaction?
White steamy fumes of the hydrogen halide are produced.
For which halide acid-base reactions does redox also take place?
Bromide and Iodide
What are the observations for a reaction of silver nitrate with each halide?
Chloride: white precipitate formed and soluble in dil NH3
Bromide: cream precipitate, not soluble in dil NH3 but is in conc NH3
Iodide: yellow precipitate formed, insoluble in NH3
