Given that cao (s) + h2o (l) → ca (oh) 2 (s), δh°rxn = - 64.8 kj/mol, how many grams of cao must react in order to liberate 525 kj of heat?

454.3 g.

Explanation:

From the given dа ta:

1.0 mol of CaO liberates → - 64.8 kJ.

? mol of CaO liberates → - 525 kJ.

∴ The no. of moles needed = (1.0 mol) ( - 525 kJ) / ( - 64.8 kJ) = 8.1 mol.

∴ The no. of grams of CaO needed = no. of moles x molar mass = (8.1 mol) (56.077 g/mol) = 454.3 g.