Ap Chem Equilibrium Frqfasrbc



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Equilibrium
  1. A reversible reaction can proceed in both the forward and backward directions. Equilibrium is when the rate of the forward reaction equals the rate of the reverse reaction. All reactant and product concentrations are constant at equilibrium.
  2. AP® Chemistry 2002 Scoring Guidelines Form B These materials were produced by Educational Testing Service ® (ETS ), which develops and administers the examinations of the Advanced Placement Program for the College Board. The College Board and Educational Testing Service (ETS) are dedicated to the principle of equal opportunity, and their.
  3. Chemical equilibriumis when the concentrations of the products and the reactants in a reaction are in balance; there is no net exchange as the rate of the forward reaction is equal to the backward reaction. A dynamic equilibriumis achieved when there is a lack of change in a system as inputs and outputs remain in balance.
  4. Heptane: C 7 H 16.Combustion is when a molecule reacts with O 2 and the products are CO 2 and H 2 O. Balancing gives 7 CO 2, 8 H 2 O, 1 heptane, and 11 O 2.

In this video Paul Andersen explains how equilibrium is achieved in a reversible reaction. When the rate of the forward reaction is equal to the rate of the reverse reaction the system is at equilibrium. Graphical analysis of equilibrium is included along with a walkthrough of several calculations.

Ap Chem Equilibrium Frq Answers

UNIT 4: EQUILIBRIUM & ACIDS / BASES Intro to Equilibrium (Sec. 1) Calculating Equilibrium Conc (Sec. 1) Equilibrium Approximation (Sec.

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Chapter 13: Chemical Equilibrium‎ > ‎

G. Le Chatelier's Principle

  • Le Chatlier's principle explains the kinetics of equilibrium reactions
  • The Principle states: 'if a change is imposed on a system at equilibrium, the position of the equilibrium will shift in a direction that tends to reduce that change'
  • this means that, the equilibrium will shift away from the side of the reaction on which a change is induced
  • a reaction will always shift in a direction to be closer to the concentration at equilibrium
  • For example: increased concentration of reactants will shift equilibrium in the direction of the forward reaction (toward the products) and visa versa
  • Pressure can also effect a reaction
  • there are three ways to manipulate a reaction using pressure:
    • add or remove a gaseous reactant or product
    • add an inert gas
    • change the volume of the container
  • adding a gaseous product will shift the reaction towards the reactants because of increase in concentration of products and increased the pressure of the container which would force the gaseous molecules to react more frequently. Removing gaseous product would shift the reaction to create more of that gaseous product because the reverse reaction could not occur.
  • adding an inert gas would not react with any of the molecules in the reaction but would increase the pressure, which would force the side of the reaction with more gaseous molecules to collide more frequently therefore shifting equilibrium away from the side with more gaseous reactants.
  • changing the volume of the container would change the pressure. Increasing the volume would cause the side with gaseous reactants to react less frequently, therefore shifting the reaction towards the side with more gaseous reactants. Decreasing the volume would increase the pressure, causing the side with more gaseous reactants to collide more frequently, shift in the reaction to the side with less gaseous molecules
    • 'the system responds by reducing its own volume'
    • as explained by the ideal gas law, at constant temperature and pressure, the volume of the gas is directly proportional to the number of moles present. :
    • V= (RT/P)n V∝n
  • A change in temperature will change the positioin of equilibrium because it changes the equilibrium constant ( as opposed to the previous ways to change the position of equilibrium which do not change the value of K)
    • if the reaction is endothermic, equilibrium will shift right
    • if the reaction ifs exothermic, equilibrium will shift left
1) Arsenic can be extracted from its ores by first reacting the ore with oxygen (called roasting) to form solid As4O6, which is then reduced to carbon: As4O6(s) + 6C(s)↔ As4(g) + 6CO(g) Predict the direction of the shift of the equilibrium position in response to each of the following changes in conditions.
a) Addition of carbon monoxide b) Addition or removal of carbon or tetraarsenic hexoxide (As4O6) c) Removal of gaseous arsenic (As4)
Solution
a) When the concentration of a substance increases, the equilibrium shifts away from that substances. Therefore the equilibrium will shift left.
b) The concentrations of pure solids don't affect equilibrium. Therefore there will be no shift in equilibrium.
c) When the concentration of a substance decreases, the equilibrium will shift towards the substance. Therefore the equilibrium will shift right.
2) Predict the shift in equilibrium position that will occur for each of the following processes when the volume is reduced.
a) The preparation of liquid phosphorus trichloride by the reaction: P4(s) + 6Cl2(g)↔4PCl3(l)
b) The preparation of gaseous phosphorous pentachlordie according to the equation: PCl3(g) + Cl2(g)↔PCl5(g)
c) The reactionof phosphorous trichloride with ammonia: PCl3(g) + 3NH3(g)↔P(NH2)3(g) + 3HCl(g)
Solution
a) Decreasing the volume does not effect solids or liquids, only gases. The equilibrium will shift to the side with less gaseous molecules. Since the left side has 6 gaseous molecules and the right side none, the equilibrium will shift right.
b)Since the product side has one gaseous molecule and the reactan side has two, the equilibrium will shift right.
c) Since both sides have four gaseous molecules there will be no shift in equilibrium position.