Internal Energy:

$\overline{){\mathbf{\u2206}}{\mathbf{E}}{\mathbf{=}}{\mathbf{q}}{\mathbf{+}}{\mathbf{w}}}$

Recall that ** work (w)** is given by:

$\overline{){\mathbf{w}}{\mathbf{=}}{\mathbf{-}}{\mathbf{P\Delta V}}}$

**At constant V** → **w = 0**

$\mathbf{\u2206}\mathbf{E}\mathbf{=}\mathbf{q}\mathbf{+}\mathbf{0}\phantom{\rule{0ex}{0ex}}\phantom{\rule{0ex}{0ex}}\mathbf{\u2206}\mathbf{E}\mathbf{=}\mathbf{q}$

Suppose that the gas-phase reaction 2NO(g) + O_{2}(g) → 2NO_{2}(g) were carried out in a constant-volume container at constant temperature.

Would the measured heat change represent ΔH or ΔE?

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