Chemistry · Chapter 5

Products Minus Reactants

One table of standard formation enthalpies answers almost any reaction. Step through the sums and watch the two shelves settle either side of the elements.

Measured from the elementsthe dashed line is zero

Elements in standard states, the shared zero every element in its most stable form has no formation enthalpy Both shelves are drawn to the same scale.

Pick a reaction

0.0kJ exothermic
Press next step to begin.

The workingcoefficient times value

SubstancenΔHf°n × ΔHf°

Values are standard formation enthalpies in kJ/mol near 25 °C. Any element in its standard state carries zero, so oxygen gas adds nothing to the reactant sum.