O-LevelChemistryRates of Reaction5070/22 · Oct/Nov 2021 · Q65 Marks
Phosphorus reacts with hydrogen to produce phosphine, PH3. 2P + 3H2 → 2PH3 The reaction is endothermic.
- (a)Complete the energy profile diagram for this reaction. Label reactants, products and ∆H. [Figure 6.1][2]
- (b)Explain, in terms of bond breaking and bond forming, why the reaction is endothermic.[2]
- (c)Phosphine reacts with oxygen to form phosphorus(V) oxide, P4O10, and water. Complete the equation for this reaction. PH3 + ..... 02 → P4010 + H₂O[1]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2021). The mark or mark type is shown in brackets.
- [2] reactants on the left and products on the right and reactant line below product line (1)
- arrow upwards between reactants and products with ∆H label (1)
- [2] bond breaking endothermic and bond making exothermic / (thermal) energy absorbed to break bonds and (thermal) energy released on making bonds (1)
- more energy absorbed than released (1)
- [1] 4PH3 + 8O2 → P4O10 + 6H2O
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