A student writes the electron arrangement of calcium, atomic number 20, as 2,8,10.
.1
Explain the correction needed for a neutral calcium atom.
[3 marks].2
Explain one incorrect prediction that could follow from the student arrangement.
[2 marks]OCR Gateway GCSE Chemistry June 2024 Paper 3
5 questions on this paper's topics
32:001 of 5
A catalyst changes the highest point of a reaction profile from 170 kJ to 115 kJ. Reactants remain at 40 kJ and products at 15 kJ.
.1
Calculate the catalysed activation energy.
[2 marks].2
Evaluate the statement: "The catalyst releases an extra 55 kJ, so the reaction becomes more exothermic."
[2 marks]An oxygen molecule contains two oxygen atoms. Each atom has six outer electrons.
.1
Explain the bonding needed for both atoms to achieve full outer shells.
[3 marks].2
Explain why a line drawing O=O does not show every electron.
[2 marks]In a microscale experiment, 0.030 mol aluminium is mixed with 0.030 mol chlorine molecules. .
.1
Calculate the amount of aluminium chloride formed.
[3 marks].2
Calculate the amount of aluminium remaining.
[3 marks].3
Explain why doubling only the aluminium would not increase the product amount.
[2 marks]Two colourless liquids form a mixture. Liquid A boils at 56 °C and liquid B at 100 °C. A student wants to collect the liquid richer in A.
.1
Explain how fractional distillation separates the liquids.
[3 marks].2
Explain why one collected fraction is not guaranteed to be perfectly pure.
[2 marks]