Questions and Answers
When a reaction is at equilibrium, what is true about the rates of the forward and reverse reactions?
The rate of the forward reaction is equal to the rate of the reverse reaction.
What is the equilibrium constant Keq?
Concentration of Products/Concentration of Reactants.
In the equilibrium constant, which of the following is NOT included?
If the reaction is gaseous, what does Keq use instead of concentration?
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If you add more products or reactants, the Keq constant will change.
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When will the Keq change?
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What does Keq tell you about the reaction?
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For the reaction 2COF2 yields CO2 + CF4 and Keq=2, what happens if Q > Keq?
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What does Le Chatelier's Principle state?
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What happens to the reaction N2 (g) + 3H2(g) yields 2NH3(g) + heat when ammonia is added?
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Study Notes
Equilibrium Basics
- At equilibrium, the rate of the forward reaction equals the rate of the reverse reaction, resulting in no net change in concentration.
- Dynamic equilibrium implies molecules are still reacting although concentrations remain constant.
Equilibrium Constant (Keq)
- Keq is calculated as the concentration of products divided by the concentration of reactants.
- Coefficients in chemical equations serve as exponents for concentrations in the Keq expression.
Exclusions from Keq Calculation
- Solids (s) and pure liquids (l) are not included in the equilibrium constant expression.
- Only gases (g) and aqueous (aq) solutions are factored into the calculation.
Gaseous Reactions and Partial Pressure
- For gaseous reactions, partial pressures are used instead of concentrations, represented as Kp.
Stability of Keq
- The Keq constant remains unchanged regardless of the addition of products or reactants.
- Shift in reaction direction occurs, but Keq remains constant.
Influences on Keq
- changes in temperature will alter the value of Keq, whereas shifts in concentration or pressure will not.
Understanding Keq Values
- A Keq greater than 1 indicates a favoring of products, while a Keq less than 1 suggests reactants are favored.
- If the reaction quotient (Q) is less than Keq, the reaction shifts forward to produce more products.
- Conversely, if Q is greater than Keq, the reaction will shift backward to produce more reactants.
Example Calculation
- For the reaction 2COF2 ↔ CO2 + CF4 with Keq=2, calculate Q:
- Q = [CO2][CF4]/[COF2]^2.
- Given conditions yield Q=4; since Q > Keq, the reaction will shift towards the reactants.
Le Chatelier's Principle
- States that a system at equilibrium will adjust to counteract any imposed changes, reestablishing equilibrium.
Reaction Adjustments
- Adding ammonia shifts the equilibrium left towards reactants as it increases Q.
- Removing ammonia decreases Q, shifting the reaction to the right towards products.
- Adding hydrogen increases reactants leading to a shift right towards products.
- Removing nitrogen decreases reactants, shifting the reaction left towards reactants.
- Decreasing volume will favor the side with fewer moles of gas; increasing volume favors the side with more gas moles.
- Adding heat shifts the equilibrium away from heat in exothermic reactions.
- Inert gases do not affect the equilibrium position but change total pressure.
- Catalysts speed up reaching equilibrium but do not affect the position of equilibrium.
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Description
Test your knowledge of key concepts in Chapter 10 on Equilibrium. This quiz covers important definitions, such as the equilibrium constant and the dynamic nature of reactions at equilibrium. Perfect for reinforcing your understanding of chemical equilibrium principles.
