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Chapter 14
Chemical Equilibrium
Term | Definition |
---|---|
Reversible Reaction | The ability of a reaction to proceed in either the forward or the reverse direction |
Dynamic Equilibrium | The point at which both the forward and the reverse reactions continue, but at equal rates, so the concentrations of the reactants and products remain constant. It is reached when the concentrations of the reactants and the products no longer change. |
Equilibrium Constant(italicized K) | The ratio at equilibrium of the concentration of the products raised to their stoichiometric coefficients divided by the concentrations of the reactants raised to their stoichiometric coefficients |
Equilibrium Constant General Equation Example | aA + bB ---> cC + dD.. where A and B are reactants, C and D are products, and a, b, c, and d are the respective stoichiometric coefficients in the chemical Equation. K = { [C]^c * [D]^d } / { [A]^a * [B]^b } |
Law of Mass Action | The relationship between the balanced chemical equation and the expression of the equilibrium constant |
The Meaning of a Large Equilibrium Constant | If the equilibrium constant for a reaction is large, the equilibrium point of the reaction lies far to the right - the concentration of products is large and the concentration of reactants is small |
The Meaning of a Small Equilibrium Constant | If the equilibrium constant for a reaction is small, the equilibrium point of the reaction lies far to the left - the concentration of products is small and the concentration of reactants is large |
Summarizing the Significance of the Equilibrium Constant | 1. K << 1..Reverse reaction favored; forward reaction does not proceeds very far.. 2. K =~ 1.Neither direction favored; forward reaction proceeds about halfway.. 3. K >> 1..Forward reaction favored; forward reaction porceeds essentially to completion |
1. Relationships between the Equilibrium Constant and the Chemical Equation | 1. If you reverse the equation. invert the equilibrium constant( Kreverse = 1 / Kforward )... 2. If you multiply the coefficients in the equation by a factor, raise the equilibrium constant to the same factor... |
2. Relationships between the Equilibrium Constant and the Chemical Equation | 3. If you add two of more individual chemical equations to obtain an overall equation, mulitply the corresponding equilibrium constants by each other to obtain the overall equilibrium constant |
Equilibrium Constant with Respect to Partial Pressure | The expression of Kp takes the form of the expression of Kc, except that we use the partial pressure of each gas in place of its concentration... Kp = Kc(RT)^Δn.. Δn = c + d - (a+b) |
Total Number of Moles for Equilibrium Constant with Respect to Partial Pressure | Δn = c + d - (a + b), which is the sum of the stoichiometric coefficients of the gaseous products minus the sum of the stoichiometric coefficients of the gaseous reactants |
Reaction Quotient(Qc) | The ratio - at any point in the reaction(does not need to be at equilibrium) - of the concentrations of the products raised to their stoichiometric coefficients divided by the concentration of the reactants raised to their stoichiometric coefficients |
The Value of Q Relative to K | The measure of the progress of the reaction toward equilibrium. At equilibrium, the reaction quotient is equal to the equilibrium constant |
Summarizing Direction of Change Predictions | The reaction quotient(Q) is a measure of the progress of a reaction toward equilibrium.. 1. Q<K Reaction goes to the right(toward products).. 2. Q>K Reaction goes to the left(toward reactants).. 3. Q=K Reaction is at equilibrium |
Le Chatelier's Principle | When a chemical system at equilibrium is disturbed, the system shifts in a direction that minimizes the disturbance |
1. Summarizing the Effect of a Concentration Change on Equilibrium | 1. Increasing the concentration of one or more of the reactants(which makes Q |
2. Summarizing the Effect of a Concentration Change on Equilibrium | 2. Increasing the concentration of on e or more of the products(which makes Q>K) causes the reaction to shift to the left(in the direction of the reactants) |
3. Summarizing the Effect of a Concentration Change on Equilibrium | 3. Decreasing the concentration of one or more of the reactants(which makes Q>K) causes the reaction to shift to the left(in the direction of the reactants) |
4. Summarizing the Effect of a Concentration Change on Equilibrium | 4. Decreasing the concentration of one or more of the products(which makes Q |
1. Summarizing the Effect of Volume Change on Equilibrium | 1. Decreasing the volume causes the reaction to shift in the direction that has the fewer moles of gas particles... 2. Increasing the volume causes the reaction to shift in the direction that has the greater number of moles of gas particles |
2. Summarizing the Effect of Volume Change on Equilibrium | 3. If a reaction has an equal number of moles of gas on both sides of a chemical equation, then change in volume produces no effect on the equilibrium.. 4. Adding an inert gas to the mixture at a fixed volume has no effect on the equilibrium |
1. Summarizing the Effect of a Temperature Change on Equilibrium | 1. Increasing the temperature causes an exothermic reaction to shift left(in the direction of the reactants); the value of the equilibrium constant decreases |
2. Summarizing the Effect of a Temperature Change on Equilibrium | 2. Decreasing the temperature causes an exothermic reaction to shift right(in the direction of the products); the value of the equilibrium constant increases. In an endothermic chemical reaction, heat is a reactant |
3. Summarizing the Effect of a Temperature Change on Equilibrium | 3. Increasing the temperature causes an endothermic reaction to shift right(in the direction of the products); the equilibrium constant increases |
4. Summarizing the Effect of a Temperature Change on Equilibrium | 4. Decreasing the temperature causes an endothermic reaction to shift left(in the direction of the reactants); the equilibrium constant decreases |