I would say it should be Einstein's famous equation of e=mc^2 which means energy =mass x the speed of light squared. With this equation Einstein showed that energy comes from a mass travelling at the speed of light squared which is a fundamental equation to explain physical phenomena.
Equilibrium constant, Kc, is defined as the ratio of the concentrations of the products over the reactants. Also, each concentration of product of reactant is powered to its coefficient.
<em>Pure solids and liquids are not taken into account in an equilibrium</em>
Thus, for the reaction:
C(s)+ 2H₂(g) ⇌ CH₄(g)
Equilibrium constant is:
<h3>Kc = [CH₄] / [H₂]²</h3>
Now, using the formula:
Kp = Kc* (RT)^Δn
<em>Where R is gas constant (0.082atmL/molK), T is the temperature of the reaction and Δn is difference in coefficients of gas products - coefficients of gas reactants (1 - 2= -1)</em>