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Chemistry Unit 2 AS

Group 7, the halogens

Physical properties, fluorine is a pale yellow gas, chlorine a greenish gas, bromine a red-brown liquid and iodine a black solid


o Fluorine is small and leads to the repulsion between non-bonding electrons because they are so close together


o The atoms…

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Reactions of halide ions

Halide ions act as reducing agents as the give away electrons and become halogen molecules


o The increase in reducing ability is linked to the size of the ions, so the larger the atom the more easily it loses an electron which is
because the electron…

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Silver fluoride No precipitate


Silver chloride White ppt Dissolves in dilute ammonia

Silver bromide Cream ppt Dissolves in concentrated
ammonia

Silver iodide Pale yellow ppt Insoluble in concentrated
ammonia




Uses of chlorine

Reaction with water


o Chlorine reacts with water in a reversible reaction to form chloric (I) acid (HClO)…

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o The elements have two electrons in an outer s-orbital. This s-orbital becomes further away from the nucleus as we go down the
group

The sizes of the atoms


o The atoms get bigger as we go down the group, the atomic radii increase because each element has an extra…

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Oxidation is loss of electrons so in all their reactions the Group 2 metals are oxidised


o The metals go from oxidation state 0 to oxidation state +2, these are redox reactions


Reaction with water


o With water we see the same trend in reactivity, the metals get more reactive…

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o The solution is first acidified with nitric or hydrochloric acid, then barium chloride solution is
added to the solution is added to the solution under test and if a sulphate is present a white
precipitate of barium sulphate is formed




The addition of acid removes a carbonate ions as…

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Other metals


o Manganese us produced by the reduction of its oxide with carbon


o Copper is reduced in a similar way. The oxide is then heated with oxide




Some copper ores are converted into solutions containing Cu2+ ions by spraying copper mining waste with dilute acid in
the presence…

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Tungsten - reduction with hydrogen


o It is used in light bulb filaments as it has a high m.p.


Like titanium it can't be reduced by carbon as a brittle carbide would form


It is extracted from its oxide WO3 at high temperatures by reduction with hydrogen




o Using a…

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Solubility

The polar bonds are not polar enough to make the Haloalkanes soluble in water


o The main intermolecular forces of attration are dipole-dipole attractions and van der Waal forces


Haloalkanes mix with hydrocarbons so they can be used as dry cleaning fluids and to remove oily stains

Boiling Points…

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o It has a lone pair of electrons which it can use to form a covalent bond


o The lone pair is situated on an electronegative atom


Therefore a nucleophile is a species that has a lone pair of electrons with which it can form a bond by donating its…

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