Answer
$\epsilon=6.76\times10^{-20}J$
Work Step by Step
It is given in the question that
$\epsilon n=539\frac{g}{cal}$
The equation can be rearranged as:
$\epsilon=\frac{539\frac{g}{cal}}{n}$........eq(1)
For $H_2O$, the number of molecules can be determined as:
$n=\frac{N_a}{m}$
where $m$ is the molar mass of water
Substituting the values of $N_a$ and $m$ into the formula and solving for $n$:
$n=\frac{6.023\times10^{23} mol^{-1}}{18\frac{g}{mol}}=3.34\times10^{22}\frac{molecules}{g}$
Now, we substitute the value of $n$ in eq(1):
$\epsilon=\frac{539\frac{g}{cal}}{\frac{3.34\times10^{22}}{g}}$
$\epsilon=6.76\times10^{-20}J$
