CHEM 112 Lecture 25: CHEM112 Lecture 25

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26 Mar 2016

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Chem112 lecture 25 acid-base additions and titrations. If an acetic acid/sodium acetate buffer solution is prepared from 100 ml of 0. 10. The pka of acetic acid is 4. 74: a. Adding strong acid and base questions: a. Determine the concentrations of h2po4 and its conjugate base that is needed to create a buffer solution of ph of 6. 8. 0. 5019: ph = pka + log ([cb]/[acid], ph = -log(6. 2 x 10-8) + log (0. 1971/0. 5019, ph = 6. 80. 0. 253 = log ( cb / a ) concentrations, you now have to work backwards! 0. 559 (0. 128 l)(0. 425 mol/l hf)(0. 559 mol oh- / 1. 559 mol hf: 0. 0190 mol oh, thus, you would need 0. 0190 mol of naoh. If the acid or the base are weak, the ep is not 7: titrating a strong acid by adding a strong base, conceptually, If a weak acid is titrated by adding a strong base, the ph will be greater than 7 at the ep.

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?

CHEM 112 Lecture 25: CHEM112 Lecture 25

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