The goal of this lesson: Evaluate experimental results showing equilibria shifts due to temperature change

Using this reversible reaction, answer the questions below:

N2O4 2NO2

(colorless) (reddish-brown)

-As the temperature increased, what happened to the N2O4 concentration?

-Was the formation of reactants or products favored by the addition of heat?

-Which reaction is exothermic? Right to left or left to right?

-If the change of enthalpy of this reaction when proceeding left to right is 14 kcal, which chemical equation is correct?

N2O4 2NO2 + 14 kcal

N2O4 2NO2, HR = +14 kcal

N2O4 + 14 kcal 2NO2

N2O4 2NO2, HR = -14 kcal

1. The concentration of N₂O₄ decrease as the temperature of the system increased.

2. The formation of products was favored by the addition of heat.

3. The reaction going from right to left is exothermic.

4. N₂O₄ → 2NO₂; HR = +14 kcal.

Explanation:

Equation of the reaction is as follows: N₂O₄ ⇄ 2NO₂

The forward reaction proceeds with an increase in temperature. As the temperature of the reaction was increased, more of the N₂O₄ decomposed to form NO₂. Therefore, the concentration of N₂O₄ deceased.

2. The formation of products, that is the forward reaction leading to formation of NO₂ was favored by the addition of heat. Thus, with increase in temperature, the concentration of NO₂ increased.

3. An endothermic reaction is a type of reaction which requires energy input in the form of heat in order to proceed.

From the observations during the reaction, an increase in temperature by the addition of heat resulted in an increase in the forward reaction, therefore, the forward reaction is endothermic and the backward reaction is exothermic. Thus, the reaction in which colorless N₂O₄ is produced, is an exothermic reaction.

4. The change in enthalpy of a reaction is the difference in the heat content of reactants and products. For exothermic reactions, enthalpy change is negative, whereas for endothermic reactions, enthalpy change is positive.

The decomposition of  N₂O₄ to NO₂ is an endothermic reaction. Hence, the correct chemical equation is: N₂O₄ → 2NO₂; HR = +14 kcal.

yes the answer is total mass in unchanged   : )