Question

2NH₃(g) + 3O₂(g) + 2CH₄(g) -> (1000 degrees Celcius, Pt-Rh) 2HCN(g) + 6H20(g)

The above reaction is used in the industrial production of hydrogen cyanide. Consider the relevant thermodynamic data from the appendices of your text. (The tabulated values ΔH°_f and S° are for 25°C. For the purposes of this question assume that ΔH° and ΔS° are invariant with temperature. This is not actually true but would generally be a reasonable approximation over "small" temperature ranges.)

Are the following statements about this process True or False?

Thermodynamically, this reaction is spontaneous only below a certain temperature.

The equilibrium position for this reaction is further to the right at higher temperatures.

The high temperature required for this process is needed for thermodynamic reasons.

At temperatures significantly lower than 1000°C this reaction is not spontaneous.

This reaction is exothermic at 1000°C.

I calculated that delta H is -939.8 kJ, delta S is 165 J/K, and delta G at 656 degrees Celcius is -1093.1 kJ. My original answer was false, true, false, false, true, but this was wrong.

Answer 1

Thermodynamically, this reaction is spontaneous only below a certain temperature: False

The equilibrium position for this reaction is further to the right at higher temperatures.: False

The high temperature required for this process is needed for thermodynamic reasons: false

At temperatures significantly lower than 1000°C this reaction is not spontaneous.: False

This reaction is exothermic at 1000°C: True