## Chem – Reactants or Products Favored

How can you tell if products or reactants are favored in equilibrium?

Sometimes questions are asked about what the equilibrium constant, K, tells you about the equation. The answer that they are looking for is either K tells you that the products are favored or the reactants are favored. If the products are favored then K will be a number larger than 1. Another way to say it is that the numerator will be large or the denominator will be small. If the reactants are favored then K will be a number smaller than 1. Another way to say it is that the numerator will be small or the denominator will be large.

One way I like to imagine and understand this concept of what the number K means is to try to fill in numbers in a ratio or fraction that would equal K. For example, if K is 3 then a fraction that could represent that is if the top of the fraction was 6 and the bottom was 2. If the top (numerator) represents the products and the bottom (denominator) represents the reactants then the products are are larger number so the products are favored.

Examples: From the equilibrium constant K tell whether the reactants or products are favored.

 K = 10 = [ 10 ] Products Favored [ 1 ] K = 2 = [ 4 ] Products Favored [ 2 ] K = 0.25 = [ 3 ] Reactants Favored [ 12 ] K = 1 / 20 = [ 2 ] Reactants Favored [ 40 ]

PRACTICE PROBLEMS: From the equilibrium constant K tell whether the reactants or products are favored.

 K = 0.4 Reactants Favored K = 2000 Products Favored K = 38 Products Favored K = 1 / 50 Reactants Favored K = 1.5 x 105 Products Favored K = 6.9 x 10-6 Reactants Favored  