The Haber process is used to produce ammonia from nitrogen and hydrogen gases: N

Question

The Haber process is used to produce ammonia from nitrogen and hydrogen gases:

N2(g)+3H2(g) -> 2NH3(g) Delta H = -92.4kJ

What will the effect on the final equilibrium amount of NH3(g) (whether it be more or less) be if a gaseous mixture originally at equilibrium at 298K is subjected to the following changes: Please explain why also.

a) more H2 is added

b)a catalyst is added

c)the mixture is transferred to a reaction vessel of greater volume

d) the partial pressure of N2 is decreased

e) the temperature is lowered to 273K

f) the partial pressure of NH3 is decreased.

Explanation / Answer

delta H is negative ..so the reaction is spontaneous and moves in the forward direction.

hence

a)

more reactant(i.e H2) is added implies more NH3 is formed..hence equilibrium conc. of NH3 increases

b)

Catalyst doesn't affect equilibrium conc. of NH3. it only increases the speed of reaction.

c) greater volume => total pressure decreases => partial pressure too decreases..but it also decreases for H2 and Nh3

since reactant moles is greater. kp increases.

hence kc increases. but concentration of NH3 decreases..

d)

partial pressure is directly proportional to N2 conc.

hence if N2 is decreased..less NH3 is formed..

hence equilibrium conc. of NH3 decreases

e)

difference in moles of products and reactants(delta n) = 2-4 = -2

kp= kc * (RT^(delta n)

hence temperature is decreased => kc increases=> more NH3 is formed.

f)

Partial pressure of NH3 decreases => conc. of NH3 decreases => reaction proceeds to form more NH3

hence equilibrium conc. of NH3 increases

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