Equilibrium Constant and Reaction Quotient At equilibrium, the concentrations of

Question

Equilibrium Constant and Reaction Quotient

At equilibrium, the concentrations of reactants and products can be predicted using the equilibrium constant, Kc, which is a mathematical expression based on the chemical equation. For example, in the reaction

aA+bB?cC+dD

Part A

A mixture initially contains A, B, and C in the following concentrations: [A] = 0.600M , [B] = 0.850M , and [C] = 0.300M . The following reaction occurs and equilibrium is established:

A+2B?C

At equilibrium, [A] = 0.470M and [C] = 0.430M . Calculate the value of the equilibrium constant, Kc.

Express your answer numerically.

where a, b, c, and d are the stoichiometric coefficients, the equilibrium constant is

where [A], [B], [C], and [D] are the equilibrium concentrations. If the reaction is not at equilibrium, the quantity can still be calculated, but it is called the reaction quotient, Qc, instead of the equilibrium constant, Kc.

Qc=[C]tc[D]td[A]ta[B]tb

where each concentration is measured at some arbitrary time t.

Explanation / Answer

Kc= [C] / [A] [B]^2

[C]= conc at equilbirium

[A] = Conc at equilibrium

[B] = Conc at equilbrium

initial [A] = 0.600M, [B] = 0.850M , and [C] = 0.300M

At equilibrium, [A] = 0.470M and [C] = 0.430M

conc of A consumed = 0.60 - 0.470 = 0.13M

so conc of B consumed should be 0.26M

so conc of B at equilibrium will be = 0.850-0.26 = 0.59M

So Kc = 0.43 / 0.47 X 0.59 = 1.55

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