A steel object of mass 45.0 g is left in damp air. After all loose material is retained, the object and corrosion products have mass 47.7 g.
.1
Calculate the percentage increase in mass.
[3 marks]
.2
Explain why the increase does not contradict conservation of mass.
[2 marks]
6 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A factory uses electrolysis to extract aluminium. One operating mixture needs 1200 energy units per batch; adding cryolite reduces the requirement to 900 units per equal batch.
.1
Calculate the percentage reduction in energy use.
[3 marks]
.2
Explain how cryolite reduces energy use and why the positive electrodes need replacement.
[3 marks]
5 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
Chlorine atoms have electron arrangement 2,8,7. Iodine atoms have more occupied electron shells but also seven outer electrons.
.1
Explain why chlorine is more reactive than iodine.
[3 marks]
.2
Compare this trend with the reactivity trend down group 1.
[2 marks]
5 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A filter designer chooses a single graphene sheet rather than a thick graphite block. Graphene consists of one layer of carbon atoms.
.1
Compare the structures and explain two resulting properties of graphene.
[3 marks]
.2
Explain why evidence for strength alone cannot establish that graphene is a suitable filter.
[2 marks]
6 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
Dilute hydrochloric acid is added to excess copper oxide. The black oxide becomes a blue-green copper chloride solution, with black solid remaining.
.1
Write the balanced equation.
[2 marks]
.2
Explain why excess copper oxide is used and how it is removed.
[2 marks]
.3
Explain why the mass of wet crystals would overestimate the mass of salt recovered.
