In a basic aqueous solution, chloromethane undergoes a substitution reaction in
ID: 627396 • Letter: I
Question
In a basic aqueous solution, chloromethane undergoes a substitution reaction in which CL- is replaced by :OH- CH3Cl+OH arrow both ways CH3)H +Cl- The equilibrium constant is . Kc = 1e16 Calculate the equilibrium concentrations of CH3CL, CH3OH , OH- and CL- in a solution prepared by mixing equal volumes of 0.1 and 0.6 . (Hint: In defining , assume that the reaction goes 100% to completion, and then take account of a small amount of the reverse reaction.) Express your answer using one significant figure. Enter your answer numerically separated by commas.Explanation / Answer
Assuming 0.1 M for CH3Cl and 0.6 M for OH ...........After adding equal volumes [CH3Cl] = 0.05 M, [OH-] = 0.3 M .......Considering complete forward reaction, [CH3OH] = [Cl-] = 0.05 M, [CH3Cl] = 0 M, [OH-] = 0.25 M .........Now considering a small amount of backward reaction, Kc = 10^16 = (0.05-X)^2 / (X) (0.25+X), Neglecting X wrt 0.05 and 0.25 => 10^16 = 0.0025 / 0.25 X => X = 10^-18 M => [CH3OH] = [Cl-] = 0.05 M, [CH3Cl] = 10^-18 M, [OH-] = 0.25 M (Final Concentration)