Commercial hydrogen is produced by a steam reforming reaction combined with a wa

Question

Commercial hydrogen is produced by a steam reforming reaction combined with a water-shift reaction to give the overall reaction, as shown below. The following free-energy data are valid at the reaction temperature. Calculate delta G degree f (in kJ/mole) at 727 degree C for the overall reaction. Give the numerical value of the equilibrium constant for the overall reaction at 1000K. The total pressure is the sum of the partial pressures (P=PCH4+PH2O+Pco+Pco2 +PH2). Given that PCH4=8.93 times 10^-3 atm., Pco=1.43 times 10^-1 atm., and PCO2=5.14 times 10^-2 atm., calculate what percent of the overall volume of gas is H_2 under equilibrium conditions at atmospheric pressure.

Explanation / Answer

a) Required Reaction = CH4 + 2H2O ----- CO2 + 4H2

Reversing the first reaction we get

CH4 ---- C + 2H2

Reversing the second reaction and multiply it by 2 we get

2H2O-----2H2 + O2

adding the 4th reaction to it directly

C + O2----CO2

we will get the desired reaction

CH4 + 2H2O ----- CO2 + 4H2

Delta G (rxn) = -19572 + 2(192713) - 395810 = -29956 J/mol = -29.956 kJ/mol

b)

Delta G = -RTln(K)

-29956 = -(8.314)(1000)ln(K)

ln(K) = 3.6030

K = e^(3.6030) = 36.7081

c) The data for the pressure of H2O is missing in order to calculate the answer, since the equilibrium constant will contant the pressure of H2O in the expression

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