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Ch.15 - Chemical Equilibrium
All textbooksMcMurry 8th EditionCh.15 - Chemical EquilibriumProblem 115
Chapter 15, Problem 115

The reaction of fumarate with water to form L-malate is catalyzed by the enzyme fumarase; Kc = 3.3 at 37°C. When a reaction mixture with [fumarate] = 1.56 * 10-3 M and [l -malate] = 2.27 * 10-3 M comes to equilibrium in the presence of fumarase at 37 °C, what are the equilibrium concentrations of fumarate and L-malate? (Water can be omit- ted from the equilibrium equation because its concentration in dilute solutions is essentially the same as that in pure water.)

Verified step by step guidance
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Step 1: Write down the equilibrium expression for the reaction. Since water is not included in the equilibrium expression, the equilibrium constant Kc for the reaction is given by [L-malate]/[fumarate].
Step 2: Set up the ICE (Initial, Change, Equilibrium) table. Initially, [fumarate] = 1.56 * 10^-3 M and [L-malate] = 2.27 * 10^-3 M. Let x be the change in concentration of fumarate and L-malate as the reaction proceeds to equilibrium.
Step 3: Write the equilibrium concentrations in terms of x. The equilibrium concentration of fumarate will be (1.56 * 10^-3 - x) M and the equilibrium concentration of L-malate will be (2.27 * 10^-3 + x) M.
Step 4: Substitute the equilibrium concentrations into the equilibrium expression and set it equal to the given Kc value of 3.3. Solve the resulting equation for x.
Step 5: Substitute the value of x back into the expressions for the equilibrium concentrations of fumarate and L-malate to find their values at equilibrium.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Equilibrium Constant (Kc)

The equilibrium constant (Kc) is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. In this case, Kc = 3.3 indicates that at equilibrium, the concentration of L-malate is 3.3 times greater than that of fumarate. Understanding Kc is essential for calculating the equilibrium concentrations of reactants and products.
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Le Chatelier's Principle

Le Chatelier's Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the system will adjust to counteract the change and restore a new equilibrium. This principle helps predict how changes in concentration, temperature, or pressure will affect the position of equilibrium, which is crucial for understanding how the concentrations of fumarate and L-malate will shift in response to their initial concentrations.
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Reaction Quotient (Q)

The reaction quotient (Q) is a measure of the relative concentrations of products and reactants at any point in time during a reaction. It is calculated using the same formula as Kc but with the current concentrations. By comparing Q to Kc, one can determine the direction in which the reaction will proceed to reach equilibrium, which is vital for solving the problem of finding the equilibrium concentrations of fumarate and L-malate.
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Related Practice
Textbook Question
The equilibrium constant Kc for the reaction N21g2 + 3 H21g2 ∆ 2 NH31g2 is 4.20 at 600 K. When a quantity of gaseous NH3 was placed in a 1.00-L reaction vessel at 600 K and the reaction was allowed to reach equilibrium, the vessel was found to contain 0.200 mol of N2. How many moles of NH3 were placed in the vessel?
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Textbook Question

Consider the following equilibrium: Ag+ (aq) + Cl-(aq) → AgCl(s) Use Le Châtelier's principle to predict how the amount of solid silver chloride will change when the equilibrium is disturbed by: (a) Adding NaCl (b) Adding AgNO3