Case 11, afternoon, 2013
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7. The A---P reaction takes place in a completely mixed-flow reactor, and its rate equation is: -rA = kCA. The reaction rate constant k is related to the reaction temperature T as follows: K = 2000exp(-4500/T), where T is the reaction temperature. The initial concentration of the reactant Ca0 is 3 kmol/m3, with a conversion rate of 80%. In order to improve production efficiency, it is planned to increase the reaction temperature from 120°C to 130°C while maintaining the same conversion rate. What is the percentage increase in yield resulting from this temperature increase? A 32.8 B 30.5 C 26.4 D 16.9 I calculated K1=0.0213, t1=187.87 ； K2=0.0283, t2=141.4 What should I do next? I would appreciate your advice.
The ratio of product to reactant is 1:1; increasing the temperature raises the rate constant, and an increase in yield corresponds to an increase in the rate: (k2 – k1)/k1 = (0.0283 – 0.0213)/0.0213 = 32.8%. Choose (A). I’ve answered so many questions yet none of the moderators have given me flowers; I’m exhausted!
With the initial concentration of the reactants remaining unchanged and the same conversion rate being maintained, what is the percentage increase in yield when the temperature is raised? It is believed that an increase in temperature merely shortens the time required at the same conversion rate, and it has no effect on the reaction equilibrium; therefore, the yield should remain the same before and after the reaction. (What is wrong with understanding it this way?) ）
A completely mixed flow reactor is a continuous reactor. So, all that is needed is to calculate the percentage increase in the reaction rate, and that is the answer. Although the same conversion rate is achieved, the time required has also been reduced. But new substances keep participating in the reaction.
It should be written as K=2000exp(-4500/T); there shouldn’t be a negative sign after the equal sign, otherwise K will have a negative value
The negative sign simply indicates that it is a reactant, with the same meaning as -rA.