4 marksFoundation and Higher5.4.2.4 The pH scale and neutralisation
A student adds an alkali gradually to an acid. The measured pH values after successive additions are 2, 4, 6, 7, 9 and 11.
.1Describe the change and identify the neutral reading.
[2 marks] .2Explain neutralisation in terms of the reacting ions.
[2 marks] 4 marksFoundation and Higher5.5.1.2 Reaction profiles
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]6 marksHigher5.3.2.1 Moles
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.
.1Calculate the minimum mass of copper oxide needed if conversion is complete.
[4 marks] .2Calculate the mass of hydrogen that reacts with this copper oxide.
[2 marks] 6 marksHigher5.2.2.5 Polymers
A sample contains very long covalent molecules. It softens when heated, does not conduct electricity and becomes solid again on cooling.
Explain these observations using a polymer model.
[6 marks]6 marksHigher5.1.1.3 The development of the model of the atom (common content with physics)
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]