Question

You mix Fe^3+ with SCN^- and form the product [FeSCN]^2+. After mixing the reactants and allowing the system to reach equilibrium, which statements are true? More than one statement is true.

a) the forward and reverse reactions continue to occur

b) the reaction stops (no molecules convert between reactant/product)

c) the forward rate constant is equal to the reverse rate constant

d) the amount of product present is constant

e) the rate of the forward reaction is equal to the rate of the reverse reaction

f) the solution color will be constant

Answer 1

The Correct Statements are A, D, E, F

When the concentrations of reactants and products have become constant, an equation is said to have reached a point of equilibrium. The consistency of measurable properties such as concentration, color, pressure and density can show a state of equilibrium.

Chemical equilibrium, a condition in the course of a reversible chemical reaction in which no net change in the amounts of reactants and products occurs. A reversible chemical reaction is one in which the products, as soon as they are formed, react to produce the original reactants. At equilibrium, the two opposing reactions go on at equal rates, or velocities, hence there is no net change in the amounts of substances involved.

The conditions that pertain to equilibrium may be given quantitative formulation. For example, for the reversible reaction A ⇋ B + C, the velocity of the reaction to the right, r₁, is given by the mathematical expression (based on the law of mass action) r₁ = k₁(A), where k₁ is the reaction-rate constant and the symbol in parentheses represents the concentration of A. The velocity of the reaction to the left, r₂, is r₂ = k₂(B)(C). At equilibrium, r₁ = r₂, therefore: