When K is small, which type of reaction is favored?

When the equilibrium constant (K) is small, it indicates that the concentration of the products at equilibrium is much lower than that of the reactants. Consequently, this suggests that the reaction does not proceed very far toward the formation of products; instead, it favors the reactant side.

In other words, a small K value leads to a higher ratio of reactants at equilibrium compared to products, implying that the forward reaction (reactants converting to products) is less favored. Therefore, the reverse reaction (products converting back to reactants) becomes more favorable, as it allows the reaction to achieve a higher concentration of reactants.

This characteristic is inherently tied to the concept of chemical equilibrium, where an equilibrium constant quantifies the relationship between reactants and products in a given system. In systems with a small K, equilibrium is reached predominantly with reactants present.

Thus, when K is small, the reverse reaction is favored, as it shifts the equilibrium back towards the reactants.