Question

The standard heat of formation of calcium oxide is -635.1 kJ/mol. How much heat is released when 3.8 grams of oxygen gas reacts with excess calcium in the formation of calcium oxide?

Answer 1

The balanced thermochemical equation is;

$Ca_{(s)}+O_{2{(g)}}\to CaO_{2{(s)}}$

From the equation, the energy change of $O_2$ from grams to moles is;

$3.8_gO_2\times$ $1mol O_2\over 16.01gO_2$ $\times$ $-635.1kJ/mol\over 1mol O_2$

$=-150kJ$