We are asked to find ΔE for the evaporation of 451 g of water at this temperature.

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

Molar mass H_{2}O = 18.02 g/mol

Calculate ΔH:

$\overline{){\mathbf{}}{\mathbf{q}}{\mathbf{}}{\mathbf{=}}{\mathbf{n}}{\mathbf{\u2206}}{{\mathbf{H}}}_{{\mathbf{vap}}}}\phantom{\rule{0ex}{0ex}}\mathbf{q}\mathbf{}\mathbf{=}\frac{\mathbf{m}}{\mathbf{M}}\mathbf{\u2206}{\mathbf{H}}_{\mathbf{vap}}\phantom{\rule{0ex}{0ex}}\mathbf{q}\mathbf{}\mathbf{=}\mathbf{\left(}\frac{\mathbf{451}\mathbf{}\overline{)\mathbf{g}}}{\mathbf{18}\mathbf{.}\mathbf{02}\mathbf{}\overline{)\mathbf{g}}\mathbf{/}\overline{)\mathbf{mol}}}\mathbf{\right)}\mathbf{(}\mathbf{40}\mathbf{.}\mathbf{7}\mathbf{}\mathbf{kJ}\mathbf{/}\overline{)\mathbf{mol}}\mathbf{)}$

**q= 1018.63 kJ **

The heat of vaporization of water at 373 K is 40.7 kJ/mol. Find ΔE for the evaporation of 451 g of water at this temperature.

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