I just need help with letters c and d. Thanks ! s) Given a buffer containing 0.2

Question

I just need help with letters c and d. Thanks ! s) Given a buffer containing 0.20 MH CCOOH and 0.42 MHiCCook? Given the Ka 10-5 a) Write a balanced equation showing how H CCOOH dissociates into its ions? Solution: b) Illustrate the changes in concen equilibrium concentrations) for the reaction. tration (x) using "ICE" scheme (initial, change and Reaction Initial Concentration(M) 1-020 Change in Concentration (M) | Equilibrium Concentration (M D.A0X What is the K, expression for the reaction and the assumption? Solution: c) d) What is the pH of a solution containing 0.20 MHCCOOH and 0.42 M H CCOOK? Solution:

Explanation / Answer

c) from dissociation equation

   Ka = [CH3COO-][H+]/[CH3COOH]

D)

   Ka =1.8*10^-5

at, equilibrium, [H+] = X

           [CH3COOH] = 0.2-X

           [CH3COO-] = 0.42+X = 0.42 M

(1.8*10^-5) = (X*0.42/(0.2-X))

X = 8.6*10^-6

[H+] = X = 8.6*10^-6 M

pH = -log[H+]

   = -log(8.6*10^-6)

   = 5.06

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