1. Define the chemical equations of redox reactions that can be used to balance the oxidation of Ni to Ni2+, and the oxidation of H2 to HF.
2. Correctly calculate the DG difference between the protection reaction that you’re proposing is that of Ni2+ oxidation.
3. Define the correct expression for the equilibrium constant, and calculate it from DG.
4. Similarly for H2/HF.
5. The presensence of NiO stabilizes Nb (V) as a soluble species in the melt (rather than a gas), thus giving us more options to evaluate for redox reactions.
6. Engineering considerations of implementing the proposed reaction. E.g. Nb metal may have limited solubility in the melt, and would be consumed at the entrance of the core, as soon as it encounters a little bit of impurities.

Each point is 1/3 of a grade point. i.e. if you missed one of these points, your grade dropped from A to A- etc.