ture; and (c) using -Go-A,H\'-TA,so to find .G at 60°C and hence Kp at the same
ID: 553180 • Letter: T
Question
ture; and (c) using -Go-A,H'-TA,so to find .G at 60°C and hence Kp at the same temperature. State the approximations employed in each case and compare your results. (Hint: From Equation 4.31, you can derive the relationship Le Chatelier's Principle 6.18 Consider the reaction 2N02 (g) N3O4 (g) 4H' =-58.04 kJ mol- Predict what happens to the system at equilibrium if (a) the temperature is raised, (b) the pressure on the sys- tem is increased, (c) an inert gas is added to the system at constant pressure, (d) an inert gas is added to the sys- tem at constant volume, and (e) a catalyst is added to the systenm 6.19 Referring to Problem 6.14, calculate the degree of dissociation of N204 if the total pressure is 10 atm. Comment on your result.Explanation / Answer
6.18
a) Enthalpy of the reaction is negative at standard conditions implying that the product is more stable than the reactants i.e. the reaction is exothermic. Now, as temperature increases, if more dinitrogen tetroxide is formed, the system will liberate more heat, which does not have the equilibrium conform with the surroundings. So,as per Le Chatlier's principle if the temperature is raised, the equilibrium will be shifted to the left, favouring decomposition of dinitrogen tetroxide.
b) The equilibrium involves reaction of two moles of reactants to yield one mole of product, both gaseous. In terms of pressure it can be seen as going from higher pressure, exerted by two moles of the reactant to lower pressure exerted by only one mole of product. Hence, if pressure is increased, the system will stabilize itself by going further into the lower pressure side i.e favouring right side of the equilibrium resulting in more formation of dinitrogen tetroxide.
An inert gas is any gas that does not participate in the reaction in the equilibrium and just contributes to increase in pressure at constant volume and decrease in partial pressures of all components at constant pressure.
c) Adding an inert gas in a gaseous equilibrium while maintaining constant pressure means that the increase in pressure by the inert gas is compensated by increasing the volume. This results in lowering of the partial pressures of all the reactants. This makes the equilibrium shift more towards the side where more moles of gas is produced. Hence, in this case, equilibrium shifts to left, favouring formation of nitrogen dioxide.
d) Adding an inert gas at constant volume implies an increase in the overall pressure of the system. However, due to the absence of change in volume, there will not be any change in the partial pressures of the reactants or products as the inert gas simply occurs in both sides of the equilibrium at the same pressure. This results in the overall equilibrium being left undisturbed.
e) Addition of a catalyst results in the decrease of activation of energy of the reaction without being consumed. Thus it speeds up both forward and backward reactions giving no change to the overall equilbrium.
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