One mole of N2 and three moles of H2 are placed in a flask at 375^∘ C. Calculate the total press

One mole of N2 and three moles of H2 are placed in a flask...

Key Concepts

Chemical Equilibrium

Chemical equilibrium is the state in which the rates of the forward and reverse reactions are equal, resulting in no net change in the concentrations of reactants and products. In gas-phase reactions, equilibrium involves a balance of partial pressures among the species involved, and this concept is crucial for understanding how systems reach and maintain a steady state despite ongoing reactions.

Equilibrium Constant (Kp)

The equilibrium constant expressed in terms of pressure, Kp, quantitatively relates the partial pressures of gaseous reactants and products at equilibrium. It is derived from the ideal gas law and reaction stoichiometry, and its value provides insight into the extent to which a reaction will proceed under a given set of conditions. In calculations, Kp helps determine how the pressure equilibrium shifts with changes in the system.

Mole Fraction

Mole fraction is a way of expressing the proportion of a particular component relative to the total number of moles in a mixture. It is used to calculate partial pressures in a gaseous equilibrium, as each gas’s partial pressure can be found by multiplying the total system pressure by its mole fraction. This concept is essential in determining the distribution of species in a chemical reaction at equilibrium.

Reaction Stoichiometry

Reaction stoichiometry involves the quantitative relationships between reactants and products in a chemical reaction. In equilibrium calculations, stoichiometry allows for the setup of relations between the changes in moles of each species as the system approaches equilibrium. It is a fundamental tool for constructing the ICE (Initial, Change, Equilibrium) table, which systematically tracks the progress of a reaction.

Partial Pressure

Partial pressure refers to the pressure that each individual gas in a mixture would exert if it occupied the entire volume of the container alone. In the context of chemical equilibria, partial pressures are related to mole fractions and the total system pressure, making them critical for applying the equilibrium constant in pressure form (Kp) to predict the composition of a gaseous mixture at equilibrium.

Transcript

00:01 So we want to know the total pressure when we have one mole of nitrogen and three moles of hydrogen.

00:15 And the balance equation for this is as follows.

00:22 So the first thing we're going to want to do is make an ice table, which stands for the initial, the change, and then what it is at equilibrium.

00:33 So we know we start with, let's get this in another color, we start with one mole here, three moles here, and initially we have no moles here.

00:48 As far as the change goes, we have minus just one x here because our coefficient is one here, minus three x here, since our coefficient is three, and then a positive 2x on the product side.

01:04 And at equilibrium, then, that means this is 1 minus x mole, 3 minus 3x mole, and a positive 2x mole for the product.

01:29 So looking at what we are given, we are given that the mole fraction at equilibrium of the product, is equivalent to 0 .21.

01:51 And it's important to know that the mole fraction is the number of moles, in this case, of our product, over the total moles.

02:25 So since we know that this equals 0 .21, we can do the equation, has 2x here over if we simplify these two and add them together we get 4 minus 2 and if we are to solve this this means that x is equivalent to 0 .35 moles given this we can now move on to find the mole fraction of n2 and h2.

03:29 So looking first at n2, we see that it would be the 1 minus x over 4 minus 2x, this is the total holes that we calculated here.

03:53 So we know that this would be the same as 1 minus 0 .35, all over 4 minus 2 times .3 5, which is equivalent to 0 .2.

04:19 Looking at h2, hydrogen, we will do similar, except that it is going to be 3 minus 3x over total number of moles.

04:36 And once we plug all that in, we find it is 0 .59.

04:46 Now, to find the total pressure for this balanced chemical equation, we're going to want to find kp, which is equivalent to the pressure of the product, raised to how many moles we have over the pressure, of our first reactant times the partial pressure of our second...

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