Topic 4B Group 7 Flashcards
What is the trend in melting temperatures down group 7?
increases down the group
Why do the melting temperatures of group 7 increase down the group?
there is an increase in the number of electrons so the strength of london forces increases
What is sublimation?
the transition of a substance directly from the solid phase to the gas phase without passing through the intermediate liquid phase
What 3 factors does electronegativity depend on?
- nuclear charge- the bigger the nuclear charge, the higher the electronegativity
- distance between the nucleus and bonding pair of electrons, the shorter the distance, the higher the electronegativity
- the shielding effect of electrons in inner energy levels, the fewer energy levels, the higher the electronegativity
What is the trend of electronegativity down group 7?
decreases down the group (fluorine is the most electronegative)
What is the trend of reactivity down group 7?
decreases down the group
Why does the reactivity of group 7 decrease down the group?
- halogens tend to react by gaining an electron to their p-shell, they’re oxidising agents
- the atoms become larger as you go down the group, and the outer e- is further from the nucleus so less attraction to the positive nucleus
- outer e- is more shielded by inner shells as you go down the group
- this means that it is harder for the atom to attract electrons so reactivity decreases
What state is fluorine at room temperature?
gas
What is the state of chlorine at room temperature?
gas
What state is bromine at room temperature?
liquid
What state is iodine at room temperature?
solid
What colour is chlorine in water?
pale yellow-green
What colour is bromine in water?
yellow/orange
What colour is bromine in cyclohexane?
darker orange/red
What colour is iodine in water?
brown
What colour is iodine in cyclohexane?
purple or violet
Give the generalisations of reactions between group 7 and group 1/2? i.e. which reactions most vigorous, product formed, type of reaction
- reactions most vigorous between top of group 7 and bottom of group 1/2
- products of the reactions are ionic salts- usually white
- redox reactions in which the halogen acts as an oxidising agent
- oxidation state of halogen from 0 to -1 and oxidation state of metal from 0 to +1 or +2 depending on group
What is the equation for lithium and chlorine?
2Li + Cl2 –> 2LiCl
What is the equation between barium and bromine?
Ba + Br2 –> BaBr2
When a more reactive halogen displaces a less reactive halogen, what is this reaction called?
displacement reaction
Which halogens displace other halogens?
- chlorine displaces bromine and iodine
- bromine displaces iodine but not chlorine
- iodine displaces neither chlorine or iodine
What type of reaction is the halogen-halide displacement reaction?
redox reaction
Define disproportionation
the simultaneous oxidation and reduction of an element in a single reaction (where one element undergoes both oxidation and reduction at the same time)
What reactions with chlorine are disproportionation?
- chlorine with water
- chlorine with cold alkali
- chlorine with hot alkali
What is formed when chlorine reacts with water?
-dissolves to form chlorine water
-some of the dissolved chlorine reacts to form a mixture of 2 acids:
hydrochloric acid (HCl)
chloric (I) acid (HClO or HOCl)
Give the reaction and oxidation states when you mix chlorine with water
Cl2(g) + H2O(l) —> HCl(aq) + HClO(aq)
0 -1 +1
What is the equation for the ionisation of chloric acid?
HClO(aq) + H2O(l) —> ClO-(aq) + H3O+(aq)
Why is chlorine used for water treatment?
chlorate acid ionises to form chlorate ions which kill bacteria in the water
What are the products of chlorine with cold dilute aqueous sodium hydroxide?
-sodium chloride
-sodium chlorate(I) =bleach
-water
(it forms the salts of the reaction between chlorine and water)
Give the equation and oxidation states of chlorine with cold dilute aqueous sodium hydroxide
Cl2 + 2NaOH —> NaCl + NaClO + H2O
0 -1 +1
What is produced when chlorine reacts with hot concentrated sodium hydroxide solution?
- sodium chloride
- sodium chlorate (V)
- water
Give the equation and oxidation states of chlorine reacting with hot concentrated sodium hydroxide solution
3Cl2 + 6NaOH —> 5NaCl + NaClO3 + 3H2O
Out of the 3 halides, Cl-, Br- and I-, which can be oxidised by chlorine?
Br- and I-
