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Chemical equilibrium

Finding a balance (between reactants & products). Chemical equilibrium. Has been reached when the concentration of reactants and products are constant Dynamic equilibrium : The rate of formation of reactants = the rate of formation of products.

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Chemical equilibrium

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  1. Finding a balance (between reactants & products) Chemical equilibrium

  2. Has been reached when the concentration of reactants and products are constant Dynamic equilibrium : The rate of formation of reactants = the rate of formation of products. K2S(aq) + CaF2(aq)  2KF(aq) + CaS(s) CaS(s)  Ca+2(aq) + S-2(aq) Chemical equilibrium

  3. K = [products]coefficients / [reactants]coefficients • For aX + bY cZ, Keq = [Z]c / [X]a[Y]b • What does it (K) mean? • If K < 1… • Reactants are favored. • If K > 1… • Products are favored. • If K = 1… • Both (or neither)are favored. The Equilibrium Constant –Keq(or just K)

  4. only pertain to gases Kp = gaseous equilibrium constant K = Kp(RT) The affects of Pressure

  5. Contain more than one phase • (solid, liquid or gas) • By definition…(moles/liter) [“pure” solid] or [“pure” liquid] = 1 ForCaS(s)  Ca+2(aq) + S-2(aq) k = [Ca+2]x[S-2] / 1 Heterogeneous Systems

  6. The value of K determines… • reaction likelyhoodNOTreaction rate. (See Ch 12.) • The reaction quotient • Q = [products]coefficients / [reactants]coefficients for the initial conditions… Compare Q & K to determine which way the reaction is likely to proceed. Applications

  7. Reaction Equation : Find K. Find [ ]’s. Calculate Q (from Initial concentrations). Compare K & Q (final vs. initial concentrations). Solve (unknowns to achieve Equilibrium). Solving Equilibrium Problems (RICE)

  8. A system at equilibrium will respond to a disruption by moving back toward equilibrium. wrtP..Increasing P favors smaller volumes. (gases) wrt[ ]…Increasing [ ] of reactants favors products and vice versa. wrtT…Increasing T favors endothermic reactions and works against exothermic reactions. Le Chatelier’s Principle

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