To determine Kc, what must be calculated?

To determine the equilibrium constant, ( K_c ), the crucial aspect is calculating the concentration of products relative to the concentration of reactants at equilibrium. The expression for ( K_c ) is defined as the ratio of the molar concentrations of the products raised to the power of their coefficients in the balanced chemical equation over the molar concentrations of the reactants raised to the power of their coefficients.

This ratio provides insight into the extent to which a reaction proceeds toward products under equilibrium conditions. A higher value of ( K_c ) indicates that the reaction favors products, while a lower value suggests that reactants are favored.

In contrast, other options do not directly relate to calculating ( K_c ). The total number of molecules in the reaction and the mass of reactants in grams do not provide the necessary concentration information required to evaluate the equilibrium constant. Similarly, while the mole fraction can help understand the composition of a mixture, it is not used in the standard equation for ( K_c ), which specifically uses molar concentrations. Thus, focusing on the concentration of products over reactants is essential for accurately determining ( K_c ).