01:160:161 Study Guide - Final Guide: Titration Curve, Barium Nitrate, Buffer Solution

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14 Apr 2014

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Buffer: solution that resists changes in ph when small quantities of acid/base are added. Ex: ch3cooh + ch3coona (mol ratio 1:1) buffer: ch3cooh + ch3coo- = mt of weak acid + its conjugate base. = mt of weak base + its conjugate acid. Ph of a buffer changes negligibly if buffer is diluted by factor of 10 w/ pure water. Buffer solutions do not have to have acid + base reacting to form new products. Added oh- from base will be removed by acid. When acid is added to buffer, amt of conj. acid increases and conj. base decreases in buffer. Added h3o+ from acid will be removed by conjugate base. When base is added to buffer, amt of conj. base increases and conj. acid decreases in buffer. Ch3cooh + h2o ch3coo- + h3o+ (ph remains stable) Ex: if hcl is added to solution w/ f- and hf, [hf] will increase.

Related Questions

CH₃COOH <-------> CH₃COO^- + H⁺

Prepared 200 ml of 0.1 M sodium acetate solution using acetic acid (1.74M, 11.493 mL) and sodium acetate (1.641g).

Prepated 200 mL of 0.1 M acetic acid solution using the stock 1.74M acetic acid solution (11.494 mL).

testing buffer capacity of solutions

Used teh acetic acid and sodium acetate soltuions containing the volumes below:

	1	2	3	4	5	6	7
Acetic Acid	18 mL	15 mL	12 mL	9 mL	6 mL	3 mL	0 mL
Acetate	0 mL	3 mL	6 mL	9 ml	12 mL	15 mL	18 mL
Buffer pH	3.27	4.14	4.45	4.73	5.01	5.39	7.41
pH with HCl	2.65	3.63	4.22	4.51	4.79	5.13	5.69
pH with NaOH	4.04	4.43	4.74	4.96	5.35	6.09	11.54

From the inital pH and ratio of weak acid to base, calculate the pK_a of acetic acid using teh Henderson-Hasselbalch equation for all the effective buffering solutions and average th?e values. How does this compare to the actual pK_a of acetic acid of 4.76? (Please show step-by-step process)

What is the observed effective pH buffering range for inital acetate buffers?

Which mixtures of acetate buffer resist pH changes to BOTH HCl and NaOH? How did you decide? Which would be the best buffer solution against added acid and base? Why?

01:160:161 Study Guide - Final Guide: Titration Curve, Barium Nitrate, Buffer Solution

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