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Properties of Equilibrium

equilibrium in reactions - when forward/reverse reactions occur at same rate  

  • ratio of partial pressures, concentrations equals constant
  • pressures no longer change
  • reaction continues to occur, but ratio stays the same (no net change)
  • can be reached from either direction

Haber Process - synthesizing ammonia from hydrogen/nitrogen 

  • world’s main source for fixed nitrogen
  • N2 + 3H2 <<>> 2NH3

equilibrium constant - only changed by temperature, not by reaction mechanism 

  • for reaction aA + bB <<>> cC + dD
  • Keq = (C concentration)c(D concentration)d / (A concentration)a(B concentration)b
  • value determined by coefficients in chemical equation
  • value greater than 1 >> equilibrium towards product side
  • value less than 1 >> equilibrium towards reactant side
  • for any reaction, constant equal to reciprocal of constant for reverse reaction
  • constant raised to power equal to number by which reaction is multiplied
  • constants multiplied together for net reactions involving 2+ steps
  • do not include pure solids, pure liquids, or solvents in finding constant

For the reaction CaCo3(s) >> CaO(s) + CO2(g), K = 0.0108. Find the equilibrium weight of CO2 if 2g of CaCo3, 2g of CaO, and 0.5g of CO2 were placed in a 1 liter flask.  

  • don't take account of solids in the reaction
  • K = [CO2] = 0.0108 mol
  • 0.0108 mol = grams CO2 / CO2 molar mass
  • 0.0108 = grams CO2 / (12 + 16 x 2)
  • grams CO2 = 0.0108 (44)
  • 0.475 g

At equilibrium for the reaction 2NO(g) + Cl2(g) >> 2NOCl, K = 51. If [NOCl] = 0.10 and [Cl2] = 0.20, find [NO]  

  • K = 51 = [NOCl]2 / ([NO]2[Cl2])
  • [NO]2 = 0.12 / 0.2 / 51 = 0.00098
  • [NO] = 0.031
Subject: 
Chemistry
Subject X2: 
Chemistry

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