For the equation N2(g)+O2(g) ⇋2 NO(g), use the following data to calculate the value of ΔHrxan^∘

For the equation N2(g)+O2(g) ⇋2 NO(g), use the following...

For the equation $\mathrm{N}_{2}(g)+\mathrm{O}_{2}(g) \leftrightharpoons 2 \mathrm{NO}(g)$, use the following data to calculate the value of $\Delta H_{\mathrm{rxan}}^{\circ}:$ \begin{tabular}{cc} \hline $\boldsymbol{T} / \mathbf{K}$ & $\boldsymbol{K}_{\mathrm{p}} / \mathbf{1 0}^{-4}$ \\ \hline 2000 & $4.08$ \\ 2100 & $6.86$ \\ 2200 & $11.0$ \\ 2300 & $16.9$ \\ 2400 & $25.1$ \\ \hline \end{tabular} Compare your answer to the value calculated from the data in Appendix D.

For the equation $\mathrm{N}_{2}(g)+\mathrm{O}_{2}(g) \leftrightharpoons 2 \mathrm{NO}(g)$,
use the following data to calculate the value of $\Delta H_{\mathrm{rxan}}^{\circ}:$ \begin{tabular}{cc}
\hline $\boldsymbol{T} / \mathbf{K}$ & $\boldsymbol{K}_{\mathrm{p}} / \mathbf{1 0}^{-4}$ \\
\hline 2000 & $4.08$ \\
2100 & $6.86$ \\
2200 & $11.0$ \\
2300 & $16.9$ \\
2400 & $25.1$ \\
\hline
\end{tabular}
Compare your answer to the value calculated from the data in Appendix D.

Key Concepts

Standard Reaction Enthalpy (?H°rxn)

Standard reaction enthalpy (?H°rxn) is a thermodynamic quantity that represents the heat absorbed or released during a chemical reaction under standard conditions. It can be determined by analyzing the temperature dependence of the equilibrium constant using the Van't Hoff equation, linking experimental data directly to the energetic changes occurring in the reaction.

Van't Hoff Equation

The Van't Hoff equation relates the change in the equilibrium constant of a reaction to the change in temperature. By plotting the natural logarithm of the equilibrium constant versus the inverse of the temperature (1/T), one can derive a linear relationship where the slope is proportional to the negative reaction enthalpy over the gas constant. This linear behavior is essential for determining the reaction’s thermodynamic parameters.

Equilibrium Constant (Kp/K)

The equilibrium constant (K) quantifies the ratio of the concentrations (or partial pressures, often denoted as Kp for gases) of products to reactants at equilibrium. It is a key parameter in thermodynamics because its value reflects the position of equilibrium and is directly connected to the standard Gibbs free energy change of the reaction.

Chemical Equilibrium

Chemical equilibrium refers to the state in a reversible chemical reaction where the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. Understanding equilibrium is fundamental to predicting how a system responds to changes in conditions such as temperature and pressure.

Transcript

00:01 In this problem, we're given some information, use that information to calculate the heat of reaction.

00:07 Okay, let's go nice purple here.

00:09 So we're going to use first this information to think about what we're doing.

00:28 And this will equal negative rt times the ln of k.

00:34 So then we can do the ln of k, equal negative heat of reaction over r times 1 over t, plus my entropy of my reaction over r.

00:57 Then we're going to do a graph, and i plugged the ln of k versus 1 over t.

01:13 I got a plot similar, not exactly, to this.

01:21 So this is like negative 1, negative 2, negative 3, 4, 5, 6.

01:30 I better go a little deeper than that.

01:43 And then over here, i had my temperature and i went 0 -004, 0 -0 -0 -4 -2, 0 -0 -0 -4 -4 -0 -4 -4 -6 -4 -4 -6, 0 -0 -0 -4 -8, 0 -0 -0 -5 -0, et cetera.

02:23 So i went from about six, right about.

02:26 Let me switch colors so you can see what i'm doing.

02:29 Negative 6.

02:30 Just tiny above and right about here.

02:33 This is very approximate.

02:36 And then five was just above point eight.

02:42 And then my other points were right here.

02:44 So it looked like this.

02:46 And i've got my equation align is 21796 x plus 3, 0942, and r squared equals 1...