Explain how the determination of the rate law equation significantly differs from the determination of the equilibrium constant keq expression.

The rate law equation is different from the determination of the equilibrium constant keq expression because rate law equation is used experimentally

And by looking at the equation of the reaction and chemicals used in the reaction equation Keq is determined.

The value of the reaction quotient, when the chemical reaction approaches the state of equilibrium, this is called equilibrium constant.