The portal has been deactivated. Please contact your portal admin.

Question Video: Recognizing Why a Reaction Does Not Reach Equilibrium Chemistry • 10th Grade

Calcium oxide can be made on a large scale by heating calcium carbonate in a furnace. The furnace uses a lot of energy when heating up to the required temperature and additional calcium carbonate is frequently added to keep the reaction running, as shown: CaCO₃ (s) ⇌ CaO (s) + CO₂ (g). Why does this reaction not reach equilibrium?

02:31

Video Transcript

Calcium oxide can be made on a large scale by heating calcium carbonate in a furnace. The furnace uses a lot of energy when heating up to the required temperature and additional calcium carbonate is frequently added to keep the reaction running, as shown. CaCO3 solid is in equilibrium with CaO solid plus CO2 gas. Why does this reaction not reach equilibrium? (A) The furnace is too hot. (B) The rate of reaction is too slow. (C) The reaction is irreversible. (D) The amount of reactants and products remains constant. (E) The furnace is not a closed system.

In order to understand why this reaction does not reach equilibrium, we first need to understand what equilibrium is. A dynamic equilibrium is an equilibrium between forward and reverse reactions where both reactions occur at the same nonzero rate. We can see that the provided reaction equation is an equilibrium equation where both the forward and reverse reactions can occur. So, the reaction could reach equilibrium if the rate of the forward and reverse reactions occur at the same rate.

However, we are told in the question that when this reaction is carried out on a large scale in a furnace, it does not reach equilibrium. If we look at the reaction equation, we can see that two of the species are solids and one is a gas. The furnace where this reaction is carried out is an open system. This means that matter can be exchanged with the surroundings. So, when the calcium carbonate is heated in the furnace, the carbon dioxide gas can escape. If the carbon dioxide is no longer present, then the furnace no longer has the compounds necessary for the reverse reaction to proceed. Without the reverse reaction, equilibrium cannot be established.

So, if an equilibrium reaction involves gases, dynamic equilibrium can only be established in a closed system, a system that does not exchange matter with its surroundings. Therefore, this reaction does not reach equilibrium because the furnace is not a closed system: answer choice (E).

Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy.