A student adds an alkali gradually to an acid. The measured pH values after successive additions are 2, 4, 6, 7, 9 and 11.
.1
Describe the change and identify the neutral reading.
[2 marks]
.2
Explain neutralisation in terms of the reacting ions.
[2 marks]
6 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
Copper oxide is reduced by hydrogen: CuO+H2→Cu+H2O. A process must produce 12.8 g copper. Ar: Cu = 64, O = 16, H = 1.
.1
Calculate the minimum mass of copper oxide needed if conversion is complete.
[4 marks]
.2
Calculate the mass of hydrogen that reacts with this copper oxide.
[2 marks]
4 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A beaker becomes colder when two substances react. A student sketches a reaction profile with products below reactants and no energy barrier.
Explain how the profile should be corrected and what each correction means.
[4 marks]
8 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
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]
5 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
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.
