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]
6 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
A student made five solutions of the same solute, all with the same concentration. The graph shows the mass of solute in each solution against the volume of the solution.
00.050.10.150.20.250.32468Volume of solution in dm³Mass of solute in g
.1
Use the graph to calculate the gradient of the line. Hence give the concentration of the solutions.
[2 marks]
.2
Calculate the mass of solute needed to make 0.75 dm³ of a solution with the same concentration.
[2 marks]
.3
Explain why the line passes through the origin.
[2 marks]
5 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
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]
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.
