Chemistry

1. 1.

   For Mg -> Mg^2+ + 2e^-, identify oxidation or reduction and explain using electrons.

   [3 marks] · no calculator
2. 2.

   Explain the role of a salt bridge in a galvanic cell and why electrons do not travel through it.

   [3 marks] · no calculator
3. 3.

   Balance MnO4^- -> Mn^2+ as a reduction half-equation in acidic solution.

   [3 marks] · no calculator
4. 4.

   Standard reduction potentials are Cu^2+/Cu = +0.34 V and Zn^2+/Zn = -0.76 V. Calculate the standard cell potential and write the spontaneous overall reaction.

   [3 marks]
5. 5.

   A current of 1.93 A flows for 1000 s through Cu^2+ solution. Assuming 100% current efficiency, calculate deposited copper mass using F = 96500 C mol^-1 and M(Cu) = 63.5 g mol^-1.

   [4 marks]
6. 6.

   A positive standard cell potential predicts feasibility, but an iron object can corrode slowly in dry air. Explain why standard potential alone cannot predict its real corrosion rate.

   [4 marks] · no calculator

Original, unofficial practice questions from SubjectScout — not official past-paper questions.