O-LevelChemistryMetals & Reactivity5070/21 · Oct/Nov 2021 · Q65 Marks
Chlorine reacts with phosphorus to form phosphorus(III) chloride. 3Cl₂ + 2P → 2PCl₃ The reaction is exothermic.
- (a)Explain in terms of bond breaking and bond forming why the reaction is exothermic.[2]
- (b)(i)When chlorine reacts with aqueous potassium iodide a brown solution is formed. Name the products of this reaction. and[1]
- (b)(ii)When aqueous bromine is added to potassium chloride there is no reaction. Explain why there is no reaction.[1]
- (c)Phosphorus(III) chloride reacts with water to form a mixture of phosphorous acid, H₃PO₃, and hydrochloric acid. Construct the equation for this reaction.[1]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2021). The mark or mark type is shown in brackets.
- [1] 6(a) bond breaking endothermic AND bond making exothermic / energy absorbed to break bonds AND energy released on making bonds
- [1] 6(a) more energy released than absorbed
- [1] 6(b)(i) iodine AND potassium chloride
- [1] 6(b)(ii) chlorine is more reactive than bromine / bromine is less reactive than chlorine
- [1] 6(c) PCl3 + 3H2O → H3PO3 + 3HCl
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