Much of the brown haze hanging over large cities is nitrogen dioxide, NO2(g). Nitrogen dioxide reacts to form dinitrogen tetroxide, N2O4(g), according to the equilibrium.
2NO2(g) N2O4(g) + 57.2 kJ
(brown) (coulorless)
Use this equilibrium to explain why the brownish haze over a large city dissapears in the winter , only to reappear again in the spring.(Assume that the atmosphere over a city constitutes a closed system.)
2NO2(g) N2O4(g) + 57.2 kJ
Adding heat, as in the summer, will push the equilibrium to the left forming more NO2 and more color. (N2O4 is colorless). The winter takes away heat and the equilibrium shifts to the right.
The following reaction is used in the commercial production of hydrogen gas.
CH4(g) + 2H2O(g) CO2(g) + 4H2(g)
a) In a closed system how would a catalyst affect the establishment of equilibrium in the system?
b) How would the concentration of H2(g) at equilibrium be affected by the use of a Ni(s) catalyst?
It's tough to follow when you post a question as a piggy back to another question. Most of the times they get lost in the shuffle. Please post a new question for new questions.
To explain why the brown haze over a large city disappears in the winter and reappears in the spring, we need to analyze the equilibrium reaction between nitrogen dioxide (NO2) and dinitrogen tetroxide (N2O4). This reaction describes the interconversion between brown (NO2) and colorless (N2O4) gases.
In the equilibrium reaction 2NO2(g) ⇌ N2O4(g) + 57.2 kJ, the forward reaction is exothermic, meaning it releases heat. The brown color is associated with the presence of NO2, while the colorless N2O4 indicates its absence.
During winter, the average temperature in many cities tends to be lower compared to other seasons. This phenomenon influences the equilibrium of the reaction since temperature affects the direction in which the reaction proceeds.
According to Le Chatelier's Principle, a system at equilibrium will shift in a way that counteracts any external disturbance. In this case, the change in temperature causes the equilibrium to shift in favor of the endothermic (heat-absorbing) direction, which is the formation of NO2.
As the temperature decreases, the equilibrium will shift to the right, meaning more N2O4 molecules will react to form NO2. Consequently, more NO2 is generated, leading to the appearance of the brownish haze over the city. The cold weather favors the brown gas over the colorless gas.
Conversely, when spring arrives, the temperature begins to rise. This increase shifts the equilibrium in the reverse direction, favoring the formation of N2O4. As a result, the concentration of NO2 decreases, causing the brown haze to disappear. The warm weather promotes the formation of the colorless gas N2O4, reducing the presence of the brown NO2 gas.
In summary, the brown haze over a large city disappears in the winter due to the shift in equilibrium towards the formation of more NO2 at lower temperatures. Conversely, in the spring, the equilibrium shifts towards the generation of more N2O4, causing the brown haze to reappear during this season.