Based on the standard free energies of formation, which of the following reactions represent a feasible way to synthesize the product?
a. 2c(s)+h2(g)? c2h2(g); ? g? f=209.2 kj/mol
b. c(s)+o2(g)? co2(g); ? g? f=? 394.4 kj/mol
c. 2c(s)+2h2(g)? c2h4(g); ? g? f=68.20 kj/mol
d. 2so(g)+o2(g)? 2so2(g); ? g? f=? 600.4 kj/mol

The standard free energies represent the total available work required for the process. It also indicates whether a process is spontaneous or not. If the standard free energy is negative, then it is spontaneous. All the reactions given have positive free energies. So, the lowest value is then chosen. The answer is:
C. 2C(s)+2H2(g)?C2H4(g); ?G?f=68.20 kJ/mol

The reaction will shift to the right