Formation Chemistry

Introduced to this material in AP Chemistry

What is it? §

A formation reaction is when all the reactants (left side of the equation) are elements and the coefficient for the single product (there can only be 1 product) must be 1.

To have the coefficient of 1 for the product you may need to use fractional coefficients for the reactants

When 1 mole of compound is formed with elements in their standard states it’s known as Enthalpy Formation

Example of Formation Reaction §

C (s) + O${}_2$ (g) -> CO${}_2$ (g)

$△$ H = -393.5 kJ

C (s) + $\frac{1}{2}$ O${}_2$ (g) -> CO (g)

$△$ H = -110.53 kJ

More examples and non-examples: