For the reaction

N2O4(g) ---> 2NO2(g) ,which of the following disturbances will cause an increase in NO2(g) concentration?

1. a decrease in temperature
2. removal of some N2O4(g)
3. need �H for the reaction to predict
4. an increase in temperature
5. an increase in pressure

An increase in temperature because the reaction is endothermic.

To determine which disturbance will cause an increase in NO2(g) concentration for the reaction N2O4(g) ---> 2NO2(g), we can consider Le Chatelier's principle. According to Le Chatelier's principle, a system will adjust itself in response to a disturbance in order to minimize the effect of the disturbance.

1. Decrease in temperature: Lowering the temperature will shift the equilibrium to the exothermic direction in order to counteract the cooling. Therefore, it will cause an increase in the concentration of NO2(g).

2. Removal of some N2O4(g): Removing N2O4(g) will decrease the concentration of this reactant. According to Le Chatelier's principle, the equilibrium will shift towards the side with fewer moles of gas, i.e., towards the side of product (2NO2(g)). This will increase the concentration of NO2(g).

3. Need �H for the reaction to predict: The enthalpy change for the reaction does not directly determine the effect on the concentration of NO2(g), so this disturbance does not provide enough information to predict the effect.

4. Increase in temperature: Raising the temperature will shift the equilibrium to the endothermic direction to counteract the heating. As a result, it will cause a decrease in the concentration of NO2(g).

5. Increase in pressure: Increasing the pressure will shift the equilibrium towards the side with fewer moles of gas. In this case, since there are fewer moles of gas on the reactant side (N2O4(g)), increasing the pressure will favor the formation of more NO2(g), causing an increase in its concentration.

Therefore, the disturbances that will cause an increase in NO2(g) concentration are:
- Decrease in temperature
- Removal of some N2O4(g)
- Increase in pressure

To determine which disturbance will cause an increase in NO2(g) concentration, we need to consider the reaction and the Le Chatelier's principle.

The given reaction is N2O4(g) ---> 2NO2(g).

1. A decrease in temperature:
According to Le Chatelier's principle, a decrease in temperature favors the exothermic reaction, which is the reverse reaction in this case. Since the forward reaction produces NO2(g), a decrease in temperature would shift the reaction in the backward direction, resulting in a decrease in NO2(g) concentration rather than an increase. Therefore, this disturbance will not cause an increase in NO2(g) concentration.

2. Removal of some N2O4(g):
Removing N2O4(g) will result in a decrease in reactant concentration. According to Le Chatelier's principle, when a reactant is removed, the reaction will shift in the forward direction to restore equilibrium. As a result, more NO2(g) will be produced to compensate for the decrease in N2O4(g). Therefore, this disturbance will cause an increase in NO2(g) concentration.

3. Need ΔH for the reaction to predict:
The enthalpy change (ΔH) for the reaction is not relevant to determining the disturbance that will cause an increase in NO2(g) concentration. Therefore, this factor does not provide any information regarding the increase in NO2(g) concentration.

4. An increase in temperature:
As mentioned earlier, a decrease in temperature favors the reverse reaction. Hence, an increase in temperature will favor the forward reaction, leading to an increase in NO2(g) concentration. Therefore, this disturbance will cause an increase in NO2(g) concentration.

5. An increase in pressure:
Increasing pressure will shift the equilibrium towards the side with fewer gas molecules according to Le Chatelier's principle. Since there are more gas molecules on the product side (2NO2(g)), increasing pressure will favor the reverse reaction and result in a decrease in NO2(g) concentration. Therefore, this disturbance will not cause an increase in NO2(g) concentration.

Based on the analysis, only the disturbance of removing some N2O4(g) or an increase in temperature will cause an increase in NO2(g) concentration. Therefore, options 2 and 4 are the correct answers.

#2 and #5 will cause a decrease in NO2. All of the others are about T; I would like to see dH for the reaction.