Chemistry 5070/22 — October/November 2014

is a simple molecular solid at room temperature and pressure,

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oxidises in the presence of water and air to form rust,

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has an atom with three occupied electron shells, the outer of which has only 5 electrons,

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has an oxide which is amphoteric,

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has a chloride of type $X\text{Cl}_3$ whose aqueous solution forms a reddish-brown precipitate on addition of aqueous ammonia,

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is a colourless diatomic gas.

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Arsenic reacts with oxygen to form arsenic(III) oxide, $\text{As}_2\text{O}_3$.

Construct the equation for this reaction.

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Arsenic(III) oxide is slightly soluble in water. A weak acid, arsenous acid, $\text{H}_3\text{AsO}_3$, is formed.

Use kinetic particle theory to explain why a $0.05\text{ mol / dm}^3$ solution of arsenous acid reacts much more slowly with magnesium ribbon than a $0.05\text{ mol / dm}^3$ solution of hydrochloric acid.