# What is the heat in kilojoules needed to vaporize 9.00 kg of water at 100°C?

May 1, 2016

Large!

#### Explanation:

We want to calculate the energy of the following reaction:

${H}_{2} O \left(l\right) + \Delta \rightarrow {H}_{2} O \left(g\right)$

This site gives the heat of vaporization of water as $40.66 \cdot k J \cdot m o {l}^{-} 1$. (There is probably a specific heat somewhere on the webz that lists the value in $J \cdot {g}^{-} 1$ of substance but I could not find it. As you will see on the table, this value is quite large, and reflects the degree of intermolecular force in the liquid.)

So we multiply this value by the amount of water in moles:

$40.66 \cdot k J \cdot m o {l}^{-} 1 \times \frac{9.00 \times {10}^{3} \cdot g}{18.01 \cdot g \cdot m o {l}^{-} 1}$ $=$ ??*kJ