A student gives this explanation: "An exothermic reaction has weak product bonds. Breaking the reactant bonds releases energy, and activation energy is the same as overall energy change."
Evaluate the explanation using bond breaking, bond formation and reaction profiles.
[6 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
In paper chromatography, dye A travels farther than dye B in the same time. Both start on the same line and the solvent front has passed both spots.
Explain the separation in terms of the mobile and stationary phases, and assess the suggestion that A must be a smaller molecule.
[4 marks]
6 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
A student claims that discovering the electron was enough evidence for the modern nuclear model of the atom.
Evaluate the claim using the development of atomic models.
[6 marks]
6 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
A student says: "Evaporating a molecular liquid makes smaller molecules because the bonds break."
Explain what happens during evaporation and evaluate the student claim.
