Question

I am not sure how to do this problem can someone show me how to do this.

The Haber process is often carried out at high temperatures to increase the rate of the reaction ( and very high pressures to drive the reaction toward products according to Le Chatelier's principle).

        Na (g) + 3 H2 (g) <--->2 NH3 (g)

a) Calculate the value of delta G for this reaction when the temperature is 800°C, and the pressure of ammonia is 2.5 stm and hydrogen and nitrogen pressures are 0.98 atm at 800°CCony

b) Calculate the value of delta H° for this reaction at 25°C

c) Is this process endothermic or exothermic at 25°C?

d) What does Lê Chatelier's principle tell us will happen to the reaction as the temperature is increased?

e) Does the reaction get more spontaneous or less spontaneous at high temperatures?

f) Offer an explanation of your above answer.

Answer 1

a)

dG = G° -RT*ln(Q)

dG =−16.48*1000 -8.314*(800)*ln(2.5^2 / (0.98*0.98^3)

dG = -29206.35481 J/mol

dG = -29.20 kJ/mol

b)

dH = Hprod - Hreact = 2*−45.94 - 0 +3*0 = -91.88 kJ/mol

c)

the process has a negative H value, therefore, it is exothermic, i.e. releases heat

d)

If we increase T, we will NOT favour products, since the reaction produced heat, that is, high T, so an icnrease of T will shift toward reactants

e)

As we increase T, this favour least the mol formation of NH3, therefore we must search low T

f)

Low T will favour enthalpy over entropy