Question

2. The Haber process was developed to convert molecular nitrogen from the atmosphere into ammonia for use infertiler. "Pested podcast is excited with this question N.)+3H. - ZH, The reaction coordinate diagram for the process is given below. It is a heterogeneous catalytic reaction, so the first step is reactants adsorbing to the surface and the last step is desorption of products from the surface. These steps have been indicated for you The subscript ad man darbed) LYN , 59 WH H NH NN, o + 2H -33 -4 | NH H. a NH 2 B, M N a (1 pt) Rased on the reaction coordinate diagra process? Be sure to include the in t how many steps are in this and the final desorption as steps b. (2 ) Which step is the rate determining step in the forward direction)? Explain your reasoning c. (pt) is the overall reaction endother thermice your reasoning d. 2 pu Will you produce more products thich Explain your reasoning (Think about you Principle!) r perature low temperature c) and apply Le Chatler's e. 12 pt) Write the equilibrium constant expression for this reaction (2 pt) The equilibrium constant for this reaction is 27x10 at 300 K At equilibrium do you expect there will be more reacts or more products Explain your reasoning (pt) Determine , from

Answer 1

Sol. a) According to adsorption theory ,starting from adsorption their are three steps :-

i) Adsorption :- In this step molecules of reactants get adsorbed on the surface of catalyst by forming loose bonds with the catalyst due to the presence of free valancies .

ii) Formation of activated complex :- When a chemical reaction occurs between reactants and the catalyst they form an intermediate called activated complex .

iii) Desorption :- In this step desorption of product occurs due to lack of its affinity for the catalyst surface .

b) The slowest step is always the rate determining step .

Step(i) and step (iii) are usually faster then step (ii) . Thus formation of activated complex step will be the rate determining step.

c) Adsorption is an exothermic process. Thus heat of adsorption decreases the need of energy of activation . Thus overall it is an exothermic reaction .

d) Lower the temperature greater would be the yield of ammonia. But if the temp is kept low the reaction will take a long time to attain the equilibrium . Tus an optimum temperature is empoyed to get a better yield .

e) Equilibrium constant expression for ammonia :-

N2 (g) + 3 H2 (g) $\rightleftharpoons$ 2 N H3 (g)  

Equilibrium constant Kc = [NH3]2/[N2] [H2]3

f) At equilibrium number of reactants is equal to number of products . because at equilibrium rate of farward reaction will be equal to rate of backward reaction .