Calculate Ho for each of the following reactions using the data in Appendix 4: 4Na(s) + O2(g)

Question:

Calculate ΔHo for each of the following reactions using the data in Appendix 4:
4Na(s) + O2(g) → 2Na2O(s)
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
2Na(s) + CO2(g) → Na2O(s) + CO(g)
Explain why a water or carbon dioxide fire extinguisher might not be effective in putting out a sodium fire.