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Equilibrium: Heat energy

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  1. Chemical equilibrium.
  2. Beginning of reaction.
  3. Haber process.
  4. Static equilibrium.
  5. Dynamic equilibrium.
  6. Heterogeneous equilibria.
  7. Manipulating the equilibrium law.
  8. Application of equilibrium constant.
  9. Reaction quotient (Q).
  10. Solving equilibrium problems.
  11. Le Chatelier's principle.
  12. The effect of change in concentration.
  13. Addition of solvent to an equilibrium system in solution.

Heat is energy flowing from a high temperature object to a low temperature object. When the two objects are at the same temperature, there is no net flow of energy or heat. That is why a covered cup of coffee will not be colder than or warmer than the room temperature after it has been in there for a few hours. This phenomenon is known as equilibrium. In this example, we deal with the flow of energy. Equilibria happen in phase transitions. For example, if the temperature in a system containing a mixture of ice and water is uniformly 273.15 K, the net amount of ice formed and the melt will be zero. The amount of liquid water will also remain constant, if no vapor escape from the system.

[...] Ammonia is formed at 2x the rate at which nitrogen is consumed. Static Equilibrium Static equilibrium does not occur in a chemical system: The reaction has stopped-no reaction is taking place. All product molecules will remain product. All unused reactant molecules will remain unreacted. Dynamic Equilibrium At some point in time, the concentrations of the reactants and products stop changing and they are in a dynamic equilibrium with each other Reactions continue to take place even if you don't see it. [...]


[...] When you have to reverse a reaction before adding them, you have to use the reciprocal of the equilibrium constant. K values are customarily written without units. Equilibrium expression involving pressure When a reaction involves gases, it is possible to express the equilibrium constant in terms of partial pressure of the gases present or in terms of molar concentration Derivation of Equilibrium Gas Laws-molar concentration of an ideal gas is directly proportional to its partial pressure, so: PiV therefore (ni/V)RT n/V is the molar concentration of the gas, represented by which is the molar concentration of the inert gas P =CRT Relationship between Kc and Kp are derived from ideal gas law Kp = Kc(RT)?n Kp = partial pressure constant (atmospheres as units) Kc = molar concentration constant (molarities as units) R = ideal gas constant l-atm/mol-K T = absolute temperature ?n = moles of product gas moles of reactant gas + - + the difference in the sums of the coefficients for the gaseous products and reactants Put values for partial pressures into the equilibrium law and solve for then compare it to K In homogeneous reactions where the number of moles of reactants and products are equal, Kc = Kp If comparing all the systems, no value of Q equals the known Kp, then none of the systems are in equilibrium Application of equilibrium constant The value of Keq indicates extent to which reactants are converted into products in a chemical reaction If large-indicates amount of products present at equilibrium is much greater than amount of reactants A very large Keq (>1010) indicates that the reaction goes to completion Equilibrium position is far to the right Generally have a large, negative ?E A very small Keq indicates very little product formed and virtually no visible reaction occurs Equilibrium position is far to the left If K = the equilibrium mixture contains approximately equal amounts of reactants and products Reaction Quotient Defined as the number obtained by entering all the required concentrations into the equilibrium law and calculating the result. [...]


[...] Concentration of a pure liquid or a pure solid is its mass divided by its own volume (density) and the density is never altered during a reaction. In practice, the concentration of the pure liquid or pure solid is considered to be equal to and only gases and dissolved solutes appear in the equilibrium constant expression. For a particular reaction at a given temperature, the value of K is constant regardless of the amounts of gases that are mixed together (homogeneous rxn system) Although the special ratio of products to reactants define by the equilibrium expression is constant for a given reaction system at a given temperature, the equilibrium constant will not always be the same for a given reaction system. [...]

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