Syllabus Edition
First teaching 2023
First exams 2025
Explain why fluorine has a lower boiling point than chlorine.
Chlorine can be reacted with sodium hydroxide to form bleach.
Write an ionic equation for the reaction between chlorine and cold dilute sodium hydroxide solution.
Give the oxidation numbers of chlorine in each of the chlorine containing ions formed in the reaction in part (b).
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Chlorine will react with cold, dilute sodium hydroxide.
Chlorine is added to drinking water to ensure that it is safe to drink.
Use an appropriate chemical equation to explain why one of the products formed in the reaction in part (c) is classed as a weak acid.
When chlorine reacts with hot dilute sodium chloride a different product is formed. State the formula of the different product and the oxidation state of the chlorine atom in this compound.
formula
oxidation state of chlorine
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Chlorine will react with cold, dilute sodium hydroxide.
When chlorine is reacted with water the following equilibrium is established
Cl2 (aq) + H2O (l) ⇌ H+ + Cl– (aq) + HClO (aq)
oxidation state of Cl in HClO:
[1]
Suggest a disadvantage of treating water with chlorine.
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Chlorine is a strong oxidising agent. In terms of electrons define the term oxidising agent
Chlorine is added to water to kill harmful bacteria and make it safe to drink. When added in the presence of sunlight, chlorine is both oxidised and reduced.
[1]
The reaction of chlorine with water with chlorine can be described as a disproportionation reaction. If chlorine reacts with hot dilute sodium hydroxide, the same type of reaction occurs.
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The halogens can react with iron wool to produce various iron compounds including iron(III) chloride, iron(III) bromide and iron(II) iodide.
The Fe2+ ion can also react with chlorine, Cl2 and bromine, Br2.
[1]
Bromate ions are toxic and fish eggs exposed to bromate can develop disorders in the brain and spine. This can also poison humans, where symptoms include acute gastrointestinal irritation and depression of the central nervous system.
Another reaction in which bromate ions are formed is by the reaction with disinfection contaminants, such as hypochlorite, HClO, in sea water shown in the equation.
Br– + 3HClO + 3OH– → BrO3– + 3Cl– + 3H2O
State the oxidation number for Cl in HClO and Cl–.
Identify the oxidising agent in the reaction given in part (c). Explain your answer.
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