Question

For each of the questions, four choices have been provided. Select the correct alternative. In the reaction \(\mathrm{N}_{2}+\mathrm{O}_{2} \rightleftarrows 2 \mathrm{NO}-\) Heat, which of following conditions is suitable to get a good yield of \(\mathrm{NO}\) ? (a) increase in temperature (b) decrease in temperature (c) increase in pressure (d) the addition of a catalyst

Short answer

Answer: Both decrease in temperature and increase in pressure are suitable conditions to get a good yield of NO in the given reaction.

Step-by-step solution

Identify the type of reaction

In this case, the reaction given is an equilibrium reaction, as indicated by the double arrow (\(\rightleftarrows\)). The reaction is the formation of nitrogen monoxide (NO) from nitrogen (N₂) and oxygen (O₂) molecules.

Determine the effect of temperature on the reaction

The reaction is exothermic, meaning that it releases heat. According to Le Chatelier's Principle, increasing the temperature will shift the equilibrium towards the endothermic side (where heat is being absorbed). In this case, that would decrease the yield of NO. Conversely, decreasing the temperature would favor the exothermic side (where heat is released), increasing the yield of NO. Therefore, choice (a) is not suitable, while choice (b) is more appropriate.

Determine the effect of pressure on the reaction

According to Le Chatelier's Principle, an increase in pressure will shift the equilibrium towards the side with fewer moles of gas. Since the reaction has 1 mole of N₂ and 1 mole of O₂ on the reactants side (2 moles total) and 2 moles of NO on the products side, increasing the pressure would favor the side with fewer moles of gas (the products side). Therefore, choice (c) is suitable for increasing the yield of NO.

Determine the effect of a catalyst on the reaction

The addition of a catalyst will increase the rate at which the reaction reaches equilibrium, but it will not change the position of the equilibrium. It will not affect the yield of NO. Therefore, choice (d) is not suitable for increasing the yield of NO. Based on the analysis, both choices (b) decrease in temperature and (c) increase in pressure are suitable to get a good yield of NO in the given reaction.

Key concepts

Le Chatelier's Principle

Le Chatelier's Principle is a fundamental concept in chemistry that describes how a dynamic equilibrium adjusts to changes in conditions to maintain balance. When a system at equilibrium experiences a change in concentration, temperature, volume, or pressure, the equilibrium will shift to counteract the imposed change and restore a new balance.

For instance, if a reactant is added to a reaction at equilibrium, Le Chatelier's Principle predicts that the equilibrium will shift towards the formation of more products to reduce the concentration of the added reactant. Similarly, if a product is removed, the reaction will shift towards producing more of that product. This principle helps us predict the outcome of various changes in reaction conditions and is essential for optimizing industrial processes, like the synthesis of ammonia in the Haber process.

Equilibrium Reactions

Equilibrium reactions are chemical reactions where the forward and reverse reactions occur at the same rate, resulting in a stable ratio of reactants to products over time. This doesn't mean the quantities of reactants and products are equal, but that their concentrations do not change unless the system is disturbed. At equilibrium, the rate of the forward reaction (the conversion of reactants to products) equals the rate of the backward reaction (the conversion of products back to reactants).

This balance is dynamic, meaning that the reactions continue to happen, but without any net effect on the concentrations. Understanding equilibrium is important for commercial chemical reactions, as it dictates how much product can be formed and helps determine the most efficient conditions to get the desired outcome. In the case of producing nitrogen monoxide (NO), knowing the optimal temperature and pressure conditions based on equilibrium principles is crucial for maximizing yield.

Exothermic Reactions

Exothermic reactions are chemical processes that release energy, usually in the form of heat, to the surroundings. This release makes the temperature of the surrounding environment increase. The energy is usually released when new bonds are formed in the product molecules, which are more stable than the bonds in the reactants.

For an exothermic equilibrium process like the formation of NO from N₂ and O₂, it's essential to understand that adding heat (increasing temperature) will shift the equilibrium towards the reactants, as the system tries to absorb the extra energy (as per Le Chatelier's Principle). Therefore, to obtain a higher yield of NO, one would need to lower the temperature. This makes the chemical equilibrium favor the formation of products, as the heat released by the reaction is effectively removed from the system.