[NewtoAtoms]

Hello Chemists,

I have been given this question in an assignment worth 10 marks. I am a bit perplexed because I think it's a rather simply question, however it's worth 10 marks! 
Would someone be so kind to review my question and tell me if I am on the correct path?


calculate the ΔG^o(C₈H₁₈) at 25^oC of octane.

2C₈H₁₈ (l)  +  25O₂ (g) ----------> 16 CO₂ (g) + 18 H₂0 (l)
   
   ΔG^o(C₈H₁₈) = ΔH^o - TΔS^o
   ΔG^o(C₈H₁₈) = (-208.4 kJ/mol) – (298K) (0.4637 kJ/K.mol)
   ΔG^o(C₈H₁₈) = (-208.4 kJ/mol) – (138.2 kJ/mol)
   ΔG^o(C₈H₁₈) = - 346.6  kJ/mol
   However because there are 2 moles of C₈H₁₈ in the original reaction the 2ΔG^o(C₈H₁₈) = -693.2 kJ/mol

   ΔG^o_rxn= [16(-394.4 kJ/mol) + 18(-237.2 kJ/mol)] – [2(-346.6 kJ/mol) + 25(0 kJ/mol)] =
   ΔG^o_rxn= [-6310.4 kJ/mol + -4269.6 kJ/mol] – [-693.2 kJ/mol] =
   ΔG^o_rxn= [-10580 kJ/mol)] – [-693.2 kJ/mol)] = -9886.8 kJ/mol
   Therefore because ΔG^o_rxn < 0 this reaction is sponateous.

Thank you so much for your time chemists,
Have a great day!