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]OCR Gateway GCSE Combined Science June 2018 Paper 10
5 questions on this paper's topics
26:001 of 5
Three repeated demonstrations with equal samples of a group 1 metal collect hydrogen volumes of 47, 49 and 48 cm³. A separate run collects 31 cm³ after the gas tube becomes loose.
.1
Calculate the mean volume from the three valid repeated demonstrations.
[3 marks].2
Explain why the low run cannot show that the metal was less reactive.
[2 marks]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 student electrolyses concentrated aqueous potassium chloride using inert electrodes in a teacher-controlled demonstration with suitable ventilation. Potassium is more reactive than hydrogen.
.1
Predict the electrode products and explain the difference from molten potassium chloride.
[3 marks].2
Explain how charge is carried through the aqueous electrolyte and through the external metal wires.
[2 marks]A farm reduces methane emissions from manure handling from 15 tonnes CO2-equivalent to 9 tonnes per year. New equipment adds 2 tonnes CO2-equivalent per year from energy use. All other emissions are unchanged.
.1
Calculate the net annual reduction in the farm’s footprint.
[2 marks].2
Explain why methane and carbon dioxide emissions both matter, and suggest one implementation barrier.
[2 marks]