Question

Consider the phase change H2O(l) → H2O(g). Calculate ΔHrxn. HEELLLLPPP

Answer 1

you've probably got (or should look up) a table of thermodynamic values for simple molecules, like water. The \(\Delta H\) of the reaction will be :\[\Sigma \Delta H_{products} - \Sigma \Delta H_{reactants}\] These values are easily found on any thermo table.

The phase change of turning liquid water into a gas will require an input of energy, so the sign of the \(\Delta H\) should be positive