Dinitrogen tetroxide decomposes to nitrogen dioxide: N2 O4(g) ⟶2 NO2(g) ΔHrxn^∘=55.3 kJ At 29

Dinitrogen tetroxide decomposes to nitrogen dioxide: N2...

Key Concepts

Temperature Dependence of Equilibrium (van 't Hoff Equation)

The temperature dependence of the equilibrium constant is described by the van 't Hoff equation, which quantitatively relates changes in temperature to changes in the equilibrium constant. This concept is essential for predicting how increasing or decreasing the temperature will shift the equilibrium position, especially in endothermic or exothermic reactions.

Reaction Stoichiometry

Reaction stoichiometry involves the quantitative relationship between reactants and products in a chemical reaction. It is critical in determining how changes in one component affect others and in calculating the amounts or proportions of substances present at equilibrium.

Percent Decomposition

Percent decomposition (or percent dissociation) quantifies the fraction of the original reactant that has been converted into products at equilibrium. This concept is useful for comparing the extent of reaction under different conditions and for assessing the impact of temperature or pressure changes on the reaction progress.

Chemical Equilibrium

Chemical equilibrium refers to the state in which the rates of the forward and reverse reactions are equal, resulting in constant concentrations or partial pressures of reactants and products over time. The concept is fundamental in understanding how reversible reactions reach a balanced state and how changes in system conditions can shift the equilibrium position.

Equilibrium Constant

The equilibrium constant is a numerical value that relates the concentrations or partial pressures of products and reactants at equilibrium, based on the stoichiometry of the reaction. It provides insight into the extent to which a reaction proceeds and is essential for quantitatively analyzing the effects of changing conditions on the reaction system.

Transcript

00:01 In this question we've been given the decomposition of n2 or 4 that decomposes to form 2 moles of n0 and we've been asked to determine the fraction or the percentage of n2 or 4 that is decomposed so for us to do this we need to determine the final pressure of n2 or 4 and we divide that by the initial pressure of n2 or 4 this is the initial and if we multiply this by 100 over 1 we are going to get the percentage of n204 that decomposed.

00:36 So for us to determine this final, the final partial pressure of n2.

00:44 What we can do is, remember we've got two states, initial two final states.

00:51 So what we can do is to, for example, look at, for example, k2, the equilibrium constant, it's condition to the final equilibrium constant.

01:00 And we know this to be the ratio of the partial pressure of the products which is pno2 divided by the partial pressure of n204 and remember this is we have two moles that are forming from one more so remember we always have to raise the partial pressures to their respective stoichiometric coefficients so we need to raise this to the power of 2 so once we have this expression we can then determine the partial pressure of n204 as pn02 squared divided by k2.

01:40 So once we have this, we then take this value and we block it into this formula, and we already have this initial partial pressure.

01:50 This is 0 .1.

01:53 This is the initial.

01:54 So the whole purpose of this question or assignment is to determine the final partial pressure of n2 or 4.

02:02 So for us to do this, for us to do this we need a k2 and the k2 that we need we can't determine it from remember here we've got two changes two state the initial state and the final state we have k2 we need k1 and one and one formula that represents these changes is land k2 over k1 is equal to the standard and there will be change of formation of that reaction.

02:43 This should be negative divided by r multiplied by 1 over t2 minus 1 over t1.

02:51 Remember we had two initial, we had two states.

02:55 This one is, has its own temperature and this state number 2 also has its own temperature.

03:04 So with its own temperature t1, we have t2.

03:07 There is also a k1 and a k2 associated.

03:12 The standard enthalpy change here that we are looking at is the standard enthalpy change associated with the differences in states of this.

03:21 Remember, enthalpy is a state condition.

03:23 We can't have just an h enthalpy.

03:27 We always talk about the change in enthalpy.

03:29 So this change in enthalpy that is in this formula is what is the enthalpy associated with the change of state from t1.

03:37 K1 to t2k2.

03:42 So moving on, we need to determine our k1.

03:48 And remember our k1 is going to be k1 is equal to pno2 squared divided by pn204.

04:02 And this is under state 1.

04:06 And this is k1.

04:07 And for us to determine this, we look at the ice table, that is the initial change and equilibrium remember k1 is an equilibrium constant so it has to be evaluated using partial pressures at equilibrium and for us to do this we are going to say for example we have n2 or 4 and we have an o2 initial then change and then we have at equilibrium so the initial here that we have, this is going to be 0 .1 and when the reaction starts we won't be having any n or 2 so this is going to be equal to 0.

05:04 So say this changes by a factor of x we're going to say minus x here because it is depleting.

05:10 It is a reactant...

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