Flashcards in Elements of Group 7 - Inorganic chemistry Deck (76)
What is fluorine's appearance at room temperature?
Pale yellow gas
What is colour is fluorine in aqueous solution?
What is the colour of fluorine in hydrocarbon solution (e.g. hexane)?
What is chlorine's appearance at room temperature?
Pale green gas
What colour is chlorine in aqueous solution?
What colour is chlorine in hydrocarbon solution (e.g. hexane)?
What is bromine's appearance at room temperature?
Dark red/brown liquid
What colour is bromine in aqueous solution?
What colour is bromine in hydrocarbon solution (e.g. hexane)?
What is iodine's appearance at room temperature?
Grey (shiny) solid
What colour is iodine in aqueous solution?
What colour is iodine in hydrocarbon solution (e.g. hexane)?
What colour is iodine in the vapour state?
How do the boiling points of the halogens change down the group and why does this change occur?
Melting and boiling points increase down the group. This is because the number of electrons in the molecule increases down the group and so strength of London dispersion forces increases, meaning more energy is required to separate the molecules from each other and so the melting point and boiling point increase.
How does the first ionisation energy of the halogens change down the group and why does this change occur?
It decreases/becomes less endothermic down the group because atomic radius increases, as does the number of shielding shells, outweighing the increase in nuclear charge, so the force of attraction on the outer electrons is less, and so they are lost more easily.
How does the first electron affinity of the halogens change down the group and why does this change occur?
The first electron affinity decreases down the group/ becomes less endothermic as the incoming electron is further from the nucleus and has a greater shielding effect between it and the nucleus, and so the attraction for the incoming electron decreases down the group
How do the bond energies of the halogens change down the group?
Generally, bond energies decrease as the bond lengths increase. The atoms increase in size and so overlap between orbitals forming the bonds is less effective, causing the sigma bond to become longer and weaker.
The F-F bond is anomalous as the extremely short bond length brings the lone pairs of electrons closer together and the repulsion between them then causes the bond to be longer
Reaction of halogens with metals
Cl2 + Na -> 2NaCl
X2 + 2e- -> 2X-
Reaction of chlorine and hydrogen
H2 + Cl2 -> 2HCl
(Hydrogen loses 2 electrons and is oxidised, chlorine gains 2 and is reduced)
When a mixture is kept in the dark, nothing happens, but when it is illuminated then the gas explodes
Reaction of bromine and hydrogen
H2 + Br2 -> 2HBr
Requires 300°C and a platinum catalyst
Reaction of iodine and hydrogen
H2 +I2 -> 2HI
Requires 300°C and a platinum catalyst and still only reacts slowly and partially
Reaction of fluorine and hydrogen
H2 +F2 -> 2HF
Reaction as chlorine dissolves in water
Cl2 +H2O -> HCl + HOCl
What is a disproportionation reaction?
A reaction in which the same element (in the same species) is simultaneously oxidised and reduced
How does the reaction of chlorine and water explain the bleaching properties of chlorine water?
ClO- ions are the main ingredient in bleach as they kill bacteria
Dissociation of HCl (from chlorine dissolving in water)
HCl + H2O -> H3O+ + Cl -
Hydrochloric acid is fully dissociated into ions
Dissociation of HOCl (from chlorine dissolving in water)
HOCl + H2O -> H3O+ + OCl-
Ionisation of strong acid
Complete ionisation (more H+)
Ionisation of weak acid
Partial ionisation (less H+)