Consider the equilibrium between NO_2, a toxic, brown, pollutant gas and potent
ID: 970437 • Letter: C
Question
Consider the equilibrium between NO_2, a toxic, brown, pollutant gas and potent oxidizer, and N_2O_4. a colorless, very toxic, corrosive, and oxidizing gas that is often used in rocket fuel because of its hypergolic tendencies (the propellants spontaneously ignite). Assume these values are obtained at 298K and you may assume they are independent of temperature. 2 NO_2(g) N_2O_4(g) Calculate delta_rG degree value for the above reaction at 298K. Predict how the color of the mixture will change (remember NO_2 is brown color, N_2O_4 is colorless) if the temperature is increased to 1000K. Give your reasoning fully. Predict how the color of the mixture will change if the total pressure is increased. Give your reasoning fully.Explanation / Answer
A) We know,
delta-H = -58.02 KJ/mol
delta-S = -176.5 J/K/mol = 0.176 KJ/K/mol
T = 298 K
So,
delta-G = -58.02 - 298*0.176 = -110.468 KJ/mol
hence, delta- G = -110.468 KJ/mol
B.)
Basically what Le Chatelier's Principle is trying to say is that if a system in equilibrium experiences a change, then it will try and counteract that change.
In this case, the excess heat is the change experienced. To counteract the excess heat, some of it must be absorbed. Thus, the endothermic reaction in which heat is absorbed will occur at a higher rate than the other reaction.
The endothermic reaction is the backward reaction. (Equilibrium shifts to the left.) Thus, more N2O4 will be converted to NO2 than the other way round, resulting in less brown-coloured N2O4 molecules in the system. Therefore, the intensity of the brown colour of NO2 colour will increase
C.)
Basically what Le Chatelier's Principle is trying to say is that if a system in equilibrium experiences a change, then it will try and counteract that change.
When total pressure is increased , the reaction will go such that it will ocuppy less space in order to bear increases pressure. So, the reacton will go towards less no of gas molecules. So, the forward reaction is having 1 gas molecule as 2 in backward.
So, the reaction will go in forward direction. more, N2O4 molecules will be formed. So, the brown colour will fade and it will be more colourless.
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