PRE-LABORATORY QUESTIONS DETERMINATION OF THE ACID CONTENT IN VINEGAR NAME DATE

Question

PRE-LABORATORY QUESTIONS DETERMINATION OF THE ACID CONTENT IN VINEGAR NAME DATE 1. Why does the vinegar solution need to be diluted before beginning the titration? 2. A student, performing the same experiment as you, the data table below. The original solution was diluted by a factor of 5. Show all calculations needed recorded the following information Complete TRIAL Volume of diluted vinegar sample (mL) 25.00 Molarity of NaOH Initial buret reading (mL) Final buret reading (mL.) 0.0900 16.50 38.00 Volume of NaOH Moles of acetic acid (diluted) Molarity of acetic acid (diluted) Molarity of acetic acid (original) EXPERIMENT 11 161

Explanation / Answer

1) If vinegar (contains 15-20% acetic acid) is used directly for titratiomn it needs large amount of NaOH and acetic acid is a week acid only 1% of solution ionises So we dilute it to the desired concentration of acetic acid.

2) C1V1 = C2V2

C1 = 0.09 M V1 = 38-16.5 = 19.5 ml  V2 = 25 ml

0.09 x 21.5 = 25 x C2

C2 = 0.0774 M = concentration of acetic acid after dilution

No. of moles of acetic acid after dilution = Molarity x volume in lts = 0.0774 x 0.025 = 0.001935

Dilution factor = Vfinal/Vinitial = 5

Concentration of acetic acid before dilution = dilution factor x concentration of diluted acetic acid = 5 x 0.0774 = 0.387 M

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