How many molecules of NO2 are produced when 12 mol of NH3 are completely reacted? 4NH3(g) + 7O2(g) ⟶ 4NO2(g) + 6H2O(g)

The correct answer is g. Increase temperature

Explanation:

We have the following endothermic reaction at equilibrium:

2 SO₃(g) ⇄ 2 SO₂(g) + O₂(g)

According to the Le Chatelier's principle, if certain conditions of a reaction at equilibrium are changed, the system will try to contrarrest the effect of the change. The factors that can modify the equilibrium position are: concentration of reactant of products, temperature, volume and pressure (for a reaction in gas phase).

In this reaction, the changes that will shift the equilibrium position to the right (towards the formation of products) will be: the decrease in products (SO₂ or O₂), the addition of reactant (SO₃), the decrease of pressure or the increase in volume (because reactants and products are in gas phase) and the increase of temperature (because it is an endothermic reaction, so it requires heat). Remember that the presence of catalyst does not modify the equilibrium position because the catalyst accelerates the reaction by reducing the activation energy (So, the option c is not correct).

The decrease of volume will not change the equilibrium position to the right. That is because as the volume decreases, the total pressure of the gas system increases. So, the equilibrium would shift towards the direction of decreased pressure (that is, towards the formation of the lesser number of gas moles). So, the equilibrium will shift towards the left (2 moles).

From the options, the only which is correct is option g (increase temperature).