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Questions and Answers
What does it mean when the reaction quotient, $Q_c$, is less than the equilibrium constant, $K_c$?
What does it mean when the reaction quotient, $Q_c$, is less than the equilibrium constant, $K_c$?
What effect does increasing the temperature have on an exothermic reaction at equilibrium?
What effect does increasing the temperature have on an exothermic reaction at equilibrium?
Consider the following reaction: $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$. If the pressure is increased, what will happen to the equilibrium?
Consider the following reaction: $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$. If the pressure is increased, what will happen to the equilibrium?
Which of the following changes will NOT affect the equilibrium position of a reaction?
Which of the following changes will NOT affect the equilibrium position of a reaction?
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What is the correct expression for the equilibrium constant, $K_c$, for the reaction $2NO_2(g) \rightleftharpoons N_2O_4(g)$?
What is the correct expression for the equilibrium constant, $K_c$, for the reaction $2NO_2(g) \rightleftharpoons N_2O_4(g)$?
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A solution contains $Ag^+$, $Ba^{2+}$, and $Cl^-$ ions. If the solution is saturated, what is the precipitate that will form?
A solution contains $Ag^+$, $Ba^{2+}$, and $Cl^-$ ions. If the solution is saturated, what is the precipitate that will form?
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What is the relationship between $K_a$, $K_b$, and $K_w$ for a conjugate acid-base pair?
What is the relationship between $K_a$, $K_b$, and $K_w$ for a conjugate acid-base pair?
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What is the $pH$ of a $0.10 M$ solution of a weak acid with a $K_a = 10^{-5}$? (Assume the change in concentration, 'x', is negligible).
What is the $pH$ of a $0.10 M$ solution of a weak acid with a $K_a = 10^{-5}$? (Assume the change in concentration, 'x', is negligible).
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The solubility product constant, $K_{sp}$, for $CaF_2$ is $3.9 \times10^{-11}$. What is the molar solubility of $CaF_2$ in pure water?
The solubility product constant, $K_{sp}$, for $CaF_2$ is $3.9 \times10^{-11}$. What is the molar solubility of $CaF_2$ in pure water?
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Consider the following equilibrium reaction: $A(g) + B(g) \rightleftharpoons 2C(g)$. If the initial concentrations of $A$ and $B$ are both $0.10 M$ and the equilibrium concentration of $C$ is found to be $0.05 M$, what is the value of $K_c$?
Consider the following equilibrium reaction: $A(g) + B(g) \rightleftharpoons 2C(g)$. If the initial concentrations of $A$ and $B$ are both $0.10 M$ and the equilibrium concentration of $C$ is found to be $0.05 M$, what is the value of $K_c$?
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Study Notes
Dynamic Equilibrium
- Occurs when the rate of the forward reaction equals the rate of the reverse reaction.
- Example: aA + bB ⇌ cC + dD
Equilibrium Constant (Kc)
- Ratio of product concentrations to reactant concentrations at equilibrium, raised to the power of their coefficients.
- Formula: Kc = [products] / [reactants]
- Magnitude indicates whether the reaction favors products or reactants.
Le Chatelier's Principle
- If a system at equilibrium is disturbed, it shifts to counteract the disturbance.
- Changes in concentration, pressure (volume), and temperature affect equilibrium position.
- Concentration: Increasing reactants shifts right; increasing products shifts left.
- Pressure: Increasing pressure (decreasing volume) shifts the reaction towards the side with fewer moles of gas.
- Temperature: Exothermic reactions shift left with increased temperature; endothermic reactions shift right.
Calculating Qc
- Reaction quotient to predict equilibrium shift
- Formula: Qc = [products] / [reactants]
- Compare Qc to Kc:
- Qc < Kc: Reaction shifts right (must form products)
- Qc > Kc: Reaction shifts left (must form reactants)
- Qc = Kc : Reaction is at equilibrium
Calculating Ksp
- Solubility product constant for sparingly soluble salts.
- Formula: Ksp = [cation]^a [anion]^b (e.g., PbCl2(s)⇌Pb2+(aq)+2Cl−(aq))
- Examples involving the equilibrium of precipitate formation, and how to solve for unknown concentrations.
Calculating Qsp
- Ion product of a solution containing one or more ionic species.
- Formula: Qsp = [cation]a [anion]b
- Compare Qsp and Ksp:
- Qsp < Ksp: No precipitate forms
- Qsp > Ksp: Precipitate forms
- Qsp = Ksp: Solution is saturated
Kw Calculations
- Water's ion product constant at 25°C.
- Kw = [H3O+][OH−] = 1.0 × 10⁻¹⁴
Acid/Base Dissociation Constant
- Key formulas:
- Ka = [H3O+][A⁻] / [HA]
- Kb = [OH⁻][HB⁺] / [B]
- Ka × Kb = Kw
- Calculating % dissociation: ([H3O⁺] / [acid initial]) × 100
- pH + pOH = 14, and the relationship between pH and [H3O⁺] (p and log)
Approximating
- When Kc value (or Ka, or Kb) is significantly smaller than initial concentrations.
- If initial concentration ≥ 500 × Kc Value, ignore x or the change in concentration
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Description
Test your understanding of dynamic equilibrium, equilibrium constants, and Le Chatelier's principle with this quiz. Explore how concentration, pressure, and temperature changes affect the position of equilibrium and learn how to calculate the reaction quotient (Qc).
