Unformatted text preview: 2 ] which reacts. [H 2 ] [I 2 ] [HI] initial 2.0 2.0 5.0 changexx + 2 x* equilibrium 2.0  x 2.0  x 5.0 + 2x * the 2 comes from the reaction stoichiometry. [HI] 2 (5.0 + 2x) 2 K c =  =  = 46 [H 2 ][I 2 ] (2.0 x)(2.0 x) Since both the numerator and denominator of this fraction are perfect squares, this can be solved by taking the square root of both sides of the equation. Thus, the equation reduces to 5.0 + 2x K c =  = (46)0.5 = 6.78 2.0  x Solving for x gives 5.0 + 2x = 6.78(2.0  x) 5.0 + 2x = 13.56  6.78 x (2 + 6.78) x = 13.56  5 8.78 x = 8.56 x = 0.975 Substituting back to get the equilibrium concentrations gives [H 2 ] = 2  x = 2  0.975 = 1.025 [I 2 ] = 2  x = 2  0.975 = 1.025 [HI] = 5.0 + 2x = 5.0 + 2 (0.975) = 6.95 Check: (6.95)2/(1.025)(1.025) = 46 (Your number may vary slightly depending on how you rounded off your answer.)...
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 Spring '08
 Martin
 Equilibrium, Kc, 2.0 m, 5.0 m

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