Question

The reaction $$4 \mathrm{NO}(g)+6 \mathrm{H}_{2} \mathrm{O}(g) \rightleftharpoons 4 \mathrm{NH}_{3}(g)+5 \mathrm{O}_{2}(g)$$ is strongly endothermic. Will an increase in temperature shift the equilibrium position toward products or toward reactants?

Short answer

An increase in temperature will shift the equilibrium position towards the products in this endothermic reaction, as the reaction will adjust to consume the excess heat according to Le Chatelier's Principle.

Step-by-step solution

Understand Le Chatelier's Principle

Le Chatelier's principle states that if a system at equilibrium is subjected to a change in temperature, pressure, or the concentration of a component, the system will adjust its equilibrium position to counteract the change. Therefore, when temperature increases or decreases, the reaction will adjust to either absorb or release heat and attempt to maintain equilibrium.

Identify the direction of the heat exchange

In this case, we are given that the reaction is strongly endothermic, meaning it absorbs heat energy from the surroundings. The heat is absorbed as the reactants are converted into products, so we can imagine heat as a reactant itself: \[4 \mathrm{NO}(g) + 6 \mathrm{H}_{2} \mathrm{O}(g) + \text{heat} \rightleftharpoons 4 \mathrm{NH}_{3}(g) + 5 \mathrm{O}_{2}(g)\]

Determine the effect of increased temperature

According to Le Chatelier's Principle, if we increase the temperature (which is effectively increasing the heat), the reaction will adjust in order to consume the excess heat. In this case, since the reaction is endothermic, the equilibrium will shift towards the products to absorb the added heat. So, the answer to the question is: An increase in temperature will shift the equilibrium position towards the products in this endothermic reaction.

Key concepts

Endothermic Reactions

The term 'endothermic' refers to a process that absorbs heat energy from its environment. In the case of endothermic reactions, energy is required to break the bonds of the reactants, which means the reaction cannot proceed without an intake of heat. This is a crucial concept in understanding chemical reactions and their energy requirements.

When a reaction is labeled as strongly endothermic, like the conversion of nitrogen monoxide and water vapor into ammonia and oxygen in the given exercise, it signifies that a substantial amount of heat is absorbed. This has practical implications, especially when considering reaction conditions. For instance, if the temperature drops, an endotheric reaction may cease to progress because of insufficient heat to continue fueling the reaction forward.

In summary, endothermic reactions are like energy 'sponges', soaking up heat to propel the chemical transformation from reactants to products.

Chemical Equilibrium

Chemical equilibrium represents a state in which a chemical reaction and its reverse reaction occur at the same rate. Once a system reaches equilibrium, the concentrations of reactants and products stabilize and do not show any net change over time, despite the ongoing individual processes. It is a dynamic balance, not a static one, as molecules continue to react with each other.

Le Chatelier's Principle, which was used in the step by step solution, guides us in predicting how an equilibrium might shift when various external conditions are altered. Understanding equilibrium is not just academic; it has real-world applications in fields like pharmaceuticals, industrial chemistry, and environmental science, where managing reaction conditions is crucial for desired outcomes. Always remember, equilibrium doesn't mean the reactants and products are in equal amounts, but rather that their rates of formation are equivalent.

Temperature Effects on Equilibrium

Temperature can dramatically impact where an equilibrium lies. Since temperature is a measure of heat energy, changing it can either supply or remove energy from a chemical system. For endotheric reactions, increasing the temperature supplies more heat, shifting the equilibrium towards the products, as the system tries to absorb the extra heat to maintain equilibrium. Conversely, if we were dealing with an exothermic reaction where heat is released, an increase in temperature would shift the equilibrium toward the reactants.

This understanding aids in the control of various chemical processes. For instance, chemists can manipulate the yield of a product by adjusting the temperature. This knowledge is crucial for industries like chemical manufacturing where optimizing conditions for higher yields of a product can be economically beneficial. When temperatures change, the equilibrium doesn't just shift instantaneously; it's a gradual process that can be predicted and utilized strategically.