A student says: "Crude oil is a compound. Fractional distillation breaks its molecules into simpler hydrocarbons. Each fraction contains one pure substance."
Evaluate each part of this explanation.
[4 marks]AQA GCSE Chemistry June 2025 Paper 2H
5 questions on this paper's topics
27:001 of 5
An exothermic synthesis gives the following measured data. At 250 °C: equilibrium yield 80%, time to equilibrium 40 min. At 350 °C: yield 60%, time 8 min. A plant must reach equilibrium within 10 min and obtain at least 55% yield.
.1
Calculate the factor by which equilibration is quicker at 350 °C.
[2 marks].2
Justify a temperature choice from these two settings and explain why the highest yield alone is not the best criterion.
[2 marks]A reaction uses the same solution concentration at 20 °C and 35 °C. A student explains the faster reaction at 35 °C by saying particles are larger and the activation energy has decreased.
Evaluate the explanation.
[4 marks]A sample contains very long covalent molecules. It softens when heated, does not conduct electricity and becomes solid again on cooling.
Explain these observations using a polymer model.
[6 marks]A drink is prepared by dissolving 18 g of sugar and making the final solution volume 300 cm³. A 75 cm³ serving is poured out after mixing.
.1
Calculate the sugar concentration in g/dm³.
[3 marks].2
Calculate the mass of sugar in the serving.
[3 marks].3
Explain whether the remaining drink has a different concentration.
[2 marks]