The decomposition of ammonia on a platinum surface at 1129 K occurs according to
ID: 1043809 • Letter: T
Question
The decomposition of ammonia on a platinum surface at 1129 K occurs according to the following reaction: 2 NH3(g) --> N2(g) + 3 H2(g). It occurs via zero order kinetics. Use the following kinetic data which report the variation of ammonia concentration in the gas phase with time "t" to evaluate the rate constant for the reaction at 1129 K.
Suggest why the reaction exhibits zero order kinetics with respect to the concentration of ammonia in the gas phase.
103[NH3] (in M) 2.10 1.85 1.47 1.23 .86 .57 .34 t/s 0 200 400 600 800 1000 1200Explanation / Answer
The reaction exhibits zero order kinetics with respect to the concentration of ammonia in the gas phase.the reason is the surface of the catalyst(here it is platinum) is almost completely covered byNH3 molecules.The adsorption of gas on the surface cannot change by increasing the pressure or concentration of NH3.Also one of the characteristics of zeroorder reaction is the concentration of reactant decreases linearly with time.
To find out the rate constant fora zero order reaction the equation is C2=C1-K0t
Take C2=1.85 C1=2.10
t=(200-0)s=200s
Putting the values in the above equation we will get,
1.85=2.10-K0200
=>K0=(2.10-1.85)/200=0.25/200=0.00125 Ms-1
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