How much heat is released if 7.15 g cao(s) is added to 152 g of h2o(l)? cao(s) + h2o(l) → ca(oh)2(s) δh°rxn = –64.8 kj/mol?

First, we calculate the number of moles of each reactant using the formula:

Moles = mass / molecular weight

CaO:
Moles = 7.15/56 = 0.128 

Water:
Moles = 152/18 = 8.44

The reaction equation shows that the reactants must be present in an equal number of moles, so CaO will be the limiting reactant and 0.128 mole of calcium hydroxide will form.

The energy released is given by:

Heat of reaction * number of moles
= -64.8 * 0.128
= -8.29 kJ

8.29 kJ of energy will be released