Question

9. Given the following reactions 2 Fe (s) + 3 CO2 (g)→ Fe2O3 (s) + 3 CO (g) ΔHorxn = +28.0 kJ 4 CO (g) + Fe3O4 (s)→ 3 Fe (s) + 4 CO2 (g) ΔHorxn = -12.5 kJ the enthalpy of the reaction (ΔHorxn) of Fe2O3 with CO 3 Fe2O3 (s) + CO (g)→ CO2 (g) + 2 Fe3O4 (s) is_______.

10. Given the following reactions

N2 (g) + O2 (g)→ 2 NO (g)

ΔHorxn = +180.7 kJ

2 NO (g) + O2 (g)→ 2 NO2 (g)

ΔHorxn = -113.1 kJ

the enthalpy of reaction (ΔHorxn) for

4 NO (g)→ 2 NO2 (g) + N2 (g)

is__________.

Answer 1

9.

2Fe(s) + 3CO2(g) --> Fe2O3(s) + 3CO(g)    dH = +28 kJ ----------------(1)

4CO(g) + Fe3O4(s) --> 3Fe(s) + 4CO2(g)    dH = -12.5 kJ --------------(2)

multiply (1) with 3 and reverse the reaction. Multiply (2) by 2 and reverse the reaction. Add both the equations,

3Fe2O3(s) + 9CO(g) --> 6Fe(s) + 9CO2(g)         dH = 3 x -28 kJ = -84 kJ

6Fe(s) + 8CO2(g) ---> 8CO(g) + 2Fe3O4(s)        dH = 2 x +12.5 kJ = 25 kJ

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3Fe2O3(s) + CO(g) ---> 2Fe3O4(s) + CO2(g)     dHorxn = -59 kJ

10. Reverse first equation.

add both equations,

2NO(g) --> N2(g) + O2(g)          dH = -180.7 kJ

2NO(g) + O2(g) ---> 2NO2(g)    dH = -113.7 kJ

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4NO(g) ---> N2(g) + 2NO2(g)    dHorxn = -294.4 kJ