### Video Transcript

The equilibrium of a chemical
reaction can be expressed by 𝐾 c, the equilibrium constant for concentration. Find the correct equation for 𝐾 c
for the reaction shown between nitrogen and hydrogen. Three H2 plus N2 are in equilibrium
with two NH3.

The equilibrium constant for
concentration expresses a value related to the ratio between the concentration of
the reactants and the concentration of the products at equilibrium.

Let’s consider a generic reaction
at equilibrium. In this equation, the lowercase
letters represent molar coefficients and the uppercase letters represent chemical
formulas. For this general reaction, we could
write an equation to calculate the equilibrium constant for concentration. In this equation, the concentration
of the products raised to their molar coefficients is divided by the concentration
of the reactants raised to their molar coefficients. We can apply the general reaction
equation and equilibrium constant for concentration equation to the reaction given
in the question.

To write the equation for the
equilibrium constant for concentration for the given reaction, we can start by
writing the product NH3 in brackets, followed by the exponent two, the molar
coefficient which appears in front of NH3 in the chemical equation. We divide this by the concentration
of the reactants H2 and N2. Hydrogen has a molar coefficient of
three. So the concentration of hydrogen in
the equilibrium constant equation is raised to the power of three.

In conclusion, the correct equation
for 𝐾 c for the reaction between nitrogen and hydrogen is 𝐾 c equals the
concentration of NH3 squared divided by the concentration of H2 cubed times the
concentration of N2.