Investigation 4 Quiz Name: Show all calculations and report all final values wit

Question

Investigation 4 Quiz Name: Show all calculations and report all final values with the correct significant figures. In this experiment you will determine the precise concentration of Vinegar, a dilute solution of acetic acid, by titrating with a sodium hydroxide solution of known concentration, Use the list of solutions below to answer questions 1 -6. a. Vinegar solution (dilute acetic Acid, CH|COOH) b. Sodium Hydraxide (NaOH) solution of known concentratian c. Phenolphthalein solution 1. Which of the solutions is the titrant? 2. Which of the solutions will be contained in the 50-mL burette? 3. Which of the solutions is the analyte? 4. Which of the solutions will be contained in the 250-mL Erlenmeyer flask? 5. Which of the solutions is the indicator? 6. Which solution is the indicator added to? 7. Read the POSITION of the meniscus in the fol lowing burette (NOT the amount of lquid4 contained in the burette). The numbers printed represent mlliiters, Report your answer using the correct units and number of significant figures for this piece of glassware. 8. What is the equivalence point of a titration? a. Where the amount of acid and base are equal b. Where there is no base and all acid C. When the valume of base in the burette is used up d. When there is all acid and no base 17 g· Phenolphthalein is an acid/base indicator that turns pink in basic Solutions. The end-point of a titration is indicated by a visual color change. Using the definition for an end-point and an equivalence paint, explain why a dark pink salution i NOT desirable?

Explanation / Answer

Answers to the following Questions.

1. Here NaOH of known concentration is the Titrant

2. The 50mL Burrete will contain the NaOH of known strength

3. Here the solution of Acetic Acid with unknown strength is the analyte

4. We will take the Acid(AcOH) in Conical(Erlenmeyer) flask

5. Phenolpthalin is the Indicator

6. Phenolpthalin is added to the acid as it turns NaOH pink. Moreover the change in colour of the solution from colouless to pink indicates the End point

7. The reading of the Burrete is 15.7mL

8. The correct answer is option A(When conc of acid is equal to the conc of base)

9. The Phenolpthalin turns basic solution pink and no change of colour in acidic medium. So the end point is marked with slight change of colour from colouless to faint pink. This pink is due to negligible excess concentraion of base(herre NaOH). But if the colour of the solution turns dark pink this clearly indicates that the solution contains more base than acis which results in giving a pink colour.
Hence that reading can't be taken for correction analysis.

             V1S1=V2S2

The calculation of strength of the unknown can be evaluated from the above formula where V represents the volume of acid/base needed and S represents Strenghth of the Solution

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