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Ch.18 - Free Energy and Thermodynamics
Chapter 18, Problem 100

The Haber process is very important for agriculture because it converts N2(g) from the atmosphere into bound nitrogen, which can be taken up and used by plants. The Haber process reaction is N2(g) + 3 H2(g) → 2 NH3(g). The reaction is exothermic but is carried out at relatively high temperatures. Why?

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1
<Understand the Haber process: The Haber process synthesizes ammonia (NH3) from nitrogen (N2) and hydrogen (H2) gases. The balanced chemical equation is N2(g) + 3 H2(g) → 2 NH3(g).>
<Recognize the nature of the reaction: The reaction is exothermic, meaning it releases heat.>
<Consider the effect of temperature on reaction rate: Higher temperatures increase the kinetic energy of molecules, leading to more frequent and effective collisions, thus increasing the reaction rate.>
<Apply Le Chatelier's Principle: Although the reaction is exothermic, increasing the temperature shifts the equilibrium position to favor the reactants (N2 and H2). However, high temperatures are used to achieve a reasonable reaction rate despite this shift.>
<Balance between rate and yield: The process is carried out at high temperatures to ensure a faster reaction rate, even though it slightly reduces the yield of ammonia due to the equilibrium shift.>