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Chem 2 ch 14
Chapter 14
Question | Answer |
---|---|
Equilibrium | a state in which there are no observable changes as time goes by. |
Chemical Equilibrium | a state in which the rates of the forward and reverse reactions are equal. The concentrations of the reactants and products remain constant. |
Physical Equilibrium | equilibrium in which only physical properties change |
equilibrium constant | K. A number equal to the ratio of the equilibrium concentrations of products to the equilibrium concentrations of reactants, each raised to the power of its stociometric coefficient |
Law of the mass action | for a reversible reaction at quilibrium and a constant temperature, a certain ratio of reactants and product concentrations has a constant value, k (the equilibrium constant) |
K>>1 | lies to the right, favors products (greater then 10) |
K<<1 | lies to the left, favors reactants (less then 0.1) |
Homogeneous equilibrium | all reacting species are in the same phase |
Δn | moles of gaseous products-moles of gaseous reactants= (c+d)-(a+b) |
Heterogeneous equilibrium | reactions in which reactants and products are in different phases. |
Rules for writing equilibrium constant | 1. an equation for a reversal reaction is written in the opposite direction the equilibrium constant becomes the reciprocal of the original equilibrium constant 2. the value k also depends on how the equilibrium is balanced. |
reaction quotient | is calculated bu substituting the initial concentrations of the reactants and products into the equilibrium constant Kc expression |
Qc > Kc | system proceeds from the right to left to reach equilibrium |
Qc = Kc | the system is at equilibrium |
Qc < Kc | system proceeds from left to right to reach equilibrium |
Le Chatelier's Principles | if an external stress is applied to a system at equilibrium, the system adjusts in such a way that the stress is partially offset as the system reaches a new equilibrium position |
variable that can be controlled experimentally | concentration, pressure, volume, and temperature |
concentrations of gases are greatly affected by: | changes in pressure |
the greater the pressure the ______ the volume | smaller |
What is the only thing that can affect the equilibrium constant | temperature |
increasing the concentrations of products shifts the equilibrium to the | left |
decreasing concentration of products shifts the equilibrium to the | right |
increasing the concentration of reactants shifts the equilibrium to the | right |
decreasing the concentration of reactants shifts the equilibrium to the | left |
increasing pressure | shifts the equilibrium to side with the fewest moles of gas |
decreasing pressure | shifts the equilibrium to the side with the most moles of gas |
increasing volume | shifts the equilibrium to the side with the most moles of gas |
decreasing volume | shifts the equilibrium to the side with the fewest moles of gas |
temperature increases favor | endothermic reactions |
temperature decreases favor | exothermic reactions |
Adding a catalyst | does not alter the equilibrium constant, not does it shift the position of an equilibrium system. |
If a reaction can be expressed as the sum of two or more reactions, the equilibrium constant for the overall reaction is given by what? | equilibrium constants of the individual reactions. |
When the equation for a reversible reaction is written in the opposite direction, the equilibrium constant becomes what? | the reciprocal of the original equilibrium constant. |
The concentrations of the reacting species in the condensed phase are expressed in? | M |
the concentrations of the reacting species in the gaseous phase are expressed in? | M or atm |
Are the concentrations of pure solids and liquids expressed in the equilibrium constant expression? | No |
The equilibrium constant in what kind of quantity? | dimensionless |
Kc= | Kf/kr |
ICE | Initial, change, equilibrium |
increasing temp | k decreases in an exothermic reaction and K increases in an endothermic reaction |
decreasing temp | k increases in an exothermic reaction and K decreases in an endothermic reaction |
According to Le Chatelier's Principle adding a catalyst does what? | 1. Doesn't change the K 2. doesn't shift the position of an equilibrium system 3. system will reach equilibrium sooner. |
List the four factors that can shift the position of equilibrium. Which is the only one that can alter the value of the equilibrium constant? | Concentration, temperature, pressure, volume. Temperature i |
If a reaction can be expressed as the sum of two or more reactions, the equilibrium constant for the overall reaction is given by what? | equilibrium constants of the individual reactions. |
When the equation for a reversible reaction is written in the opposite direction, the equilibrium constant becomes what? | the reciprocal of the original equilibrium constant. |
The concentrations of the reacting species in the condensed phase are expressed in? | M |
the concentrations of the reacting species in the gaseous phase are expressed in? | M or atm |
Are the concentrations of pure solids and liquids expressed in the equilibrium constant expression? | No |
The equilibrium constant in what kind of quantity? | dimensionless |
Kc= | Kf/kr |
ICE | Initial, change, equilibrium |
increasing temp | k decreases in an exothermic reaction and K increases in an endothermic reaction |
decreasing temp | k increases in an exothermic reaction and K decreases in an endothermic reaction |
According to Le Chatelier's Principle adding a catalyst does what? | 1. Doesn't change the K 2. doesn't shift the position of an equilibrium system 3. system will reach equilibrium sooner. |
1. List the four factors that can shift the position of equilibrium. 2. Which is the only one that can alter the value of the equilibrium constant? | !.Concentration, temperature, pressure, volume. 2. Temperature |