AP Chemistry : Energy Diagrams

Study concepts, example questions & explanations for AP Chemistry

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Example Questions

Example Question #2 : Thermochemistry And Kinetics

The following diagram shows how the energy changes as the chemical reaction


Fig 3

A chemical engineer wants to, both, increase yield and accelerate this reaction rate. He should __________.

Possible Answers:

increase the temperature only

Use a catalyst only

 extract  continuously from the reactor and use a catalyst

extract  continuously from the reactor only

Correct answer:

 extract  continuously from the reactor and use a catalyst


"Increase the temperature" is incorrect because we have an exothermic reaction and by increasing the temperature the equilibrium constant will become smaller. An increase in temperature will shift the equilibrium toward reagents. According to the Le Chatelier's principle, by extracting  continuously from the reactor the equilibrium shifts toward the product, . Furthermore, the use of a catalyst increases the reaction rate. The Haber process to synthesize ammonia is an example of this kind of reaction.

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