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Determine the number of moles of Na(CH3COO) that must be added to 250 mL of 0.16 M CH3COOH to prepare a pH 4.70 solution. Ka = 1.8x10−5

pH Buffer composition

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Does a Buffer Stabilize pH?Calculate the initial and final pH when10.0 mL of 0.100 M HCl is added to:

(a) 100 mL of water

(b) 100 mL of a buffer which is 1.50 M in CH3COOH (pKa = 4.74) and 1.25 M in Na(CH3COO)

pH 7.00

pH 4.66 4.65

2.04

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Chapt. 16More Acids and Bases

Sec. 1Titration: Chemistry Unplugged

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Titration Experiment

acid solutionunknown concentration

strong base solution known concentration

indicator dye changes color

record volume of base

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Titration Overview (Strong Acid + Strong Base example)

Titration Curve: a graph of pH of the solution in the flask as titrant (base) is added.

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Titration Overview (Strong Acid + Strong Base example)

Equivalence Point: (known) moles of base added equals (unknown) moles of acid in sample.

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Titration Overview (Strong Acid + Strong Base example)

Indicator: Added dye that changes color at the equivalence point.

color change

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Classroom Titration Problem

The equivalence point in the titration of 20.00 mL of ??? M HCl with 0.1008 M NaOH is at 24.84 mL. What is the concentration of the HCl?

What is the pH of the equivalence point?

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Real Titration Problem

A solution of ascorbic acid has an unknown concentration. A small amount of phenolphthalein (indicator) is added to 25.00 mL of the solution, and it is titrated with 0.100 M NaOH. The first pink color is seen when 18.12 mL of NaOH solution has been added. What is the concentration of ascorbic acid in the original sample?