We’re being asked **to determine the standard enthalpy change of reaction**. Recall that **ΔH˚ _{rxn}** can be calculated from the

$\overline{){\mathbf{\u2206}}{\mathit{H}}{{\mathbf{\xb0}}}_{\mathbf{r}\mathbf{x}\mathbf{n}}{\mathbf{}}{\mathbf{=}}{\mathbf{}}{\mathbf{\u2206}}{\mathit{H}}{{\mathbf{\xb0}}}_{\mathbf{f}\mathbf{,}\mathbf{}\mathbf{p}\mathbf{r}\mathbf{o}\mathbf{d}\mathbf{u}\mathbf{c}\mathbf{t}\mathbf{s}}{\mathbf{}}{\mathbf{-}}{\mathbf{}}{\mathbf{}}{\mathbf{\u2206}}{\mathit{H}}{{\mathbf{\xb0}}}_{\mathbf{f}\mathbf{,}\mathbf{}\mathbf{r}\mathbf{e}\mathbf{a}\mathbf{c}\mathbf{t}\mathbf{a}\mathbf{n}\mathbf{t}\mathbf{s}}}$

We’re given the **ΔH˚ _{f}** for each species. The chemical equation for that reaction is:

3 NO_{2}(g) + H_{2}O(l) → 2 HNO_{3 }(aq) + NO (g)

This equation is already balanced.

Given the data in the table below, ΔH°_{rxn} for the following reaction is __________ kJ.

3NO_{2}(g) + H_{2}O(l) → 2HNO_{3 }(aq) + NO (g)

A) 64

B) 140

C) -140

D) -508

E) -64

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What scientific concept do you need to know in order to solve this problem?

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