Methanol (CH_3OH) is made industrially in two steps from CO and H_2. it is so ch
ID: 1054441 • Letter: M
Question
Methanol (CH_3OH) is made industrially in two steps from CO and H_2. it is so cheap to make that it is being considered for use as a precursor to hydrocarbon fuels such as methane (CH_4): Calculate an overall Delta G degree for the formation of CH_4 from CO and H_2. Calculate an overall Delta H degree for the formation of CH_4 from CO and H_2. Calculate an overall Delta S degree for the formation of CH_4 from CO and H_2. Is the overall reaction spontaneous? Yes no If you were designing a production facility, would you plan on carrying out the reactions in separate steps or together? in separate steps togetherExplanation / Answer
for the reaction CO(g) + 2H2(g) --------->CH3OH (l) (1)
gibbs free energy change : CO= -137 Kj/mol and CH3OH= -166 and for H2=0
gibbs free energy change for the reaction = -166-137= -29 Kj/mol
for the reaction, CH3OH(l) --------->CH4(g) +1/2O2 (2)
gibbs free energy change = -74.83 ( Gibbs free energy change of CH4) +0 ( gibbs free energy change for O2)+166=91.17 Kj/mol
addition of Eq.1 and Eq.2 gives CO+2H2----> CH4+1/2O2 deltaG= -29+91.17= 62.17 Kj/mol, deltaS = -332+162 = 170 J/mol.K
from deltaGo= deltaH 0- TdeltaSo , deltaHo= 62.17+170*298.15/1000=112.855 Kj/mol
since delta G0 is +ve the reaction is not spontaneous
it is preferable to carry out the reaction separately, Sicne 1st reaction is instantaneous.