# Problem: For which one of the following reactions will ΔH be approximately (or exactly) equal to ΔE?H2(g) + Br2(g) → 2HBr(g)H2O(l) → H2O(g)CaCO3(s) → CaO(s) + CO2(g)2H(g) + O(g) → H2O(l)CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)

###### FREE Expert Solution

Recall:

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

To have ΔE = q = ΔH, work (w) must be done. Work would be done if, for instance, the pressure changes because more gas is produced or consumed compared to what you started with.

In the given choices:

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###### Problem Details

For which one of the following reactions will ΔH be approximately (or exactly) equal to ΔE?

H2(g) + Br2(g) → 2HBr(g)

H2O(l) → H2O(g)

CaCO3(s) → CaO(s) + CO2(g)

2H(g) + O(g) → H2O(l)

CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)