Question

=4.31% 17:369 Laboratory Questions Circle the questions that have been assigned. 1. Part A.2. A 20-ml volume of previously boiled, deionized water is added to the Erlenmeyer flask to prepare the sample for titration. Explain why this volume is not critical to the analysis. 2. Part A.2. Previously boiled, deionized water is unavailable. In a hurry to pursue the analysis, deionized water (not boiled) is added. How does this attempt to expedite the analysis affect the reported percent acetic acid in vinegar: too high, too low, or unaffected? Explain. 3. Part A.2 and B.1. The 20 mL of water added to the Erlenmeyer flask is to be previously boiled, deionized water. Since water does absorb CO, from the atmosphere and since Co, dissolved in water causes it to be slightly acidic, will the use of deionized water that has nor been previously boiled cause the mass of acetic acid in the vinegar to be calculated as too high or too low? Explain. 4. Part A.2 a. In determining the percent acetic acid in vinegar, the mass of each vinegar sample is measured rather than the vol- ume. Explain. b. If the vinegar were measured volumetrically (e.g., a pipet), what additional piece of data would be needed to com- plete the calculations for the experiment?

Answer 1

Ans-1. Part A.2:

This volume is not critical because it just gives the adequate dilution for the neutralisation reaction to take palce and ease of titrtaion. Because the weight of vinegar taken is too less to titrate properly in Erlenmyer flask.

Ans-2. Part A.2:

The boiling will remove the absorbed CO2 which gives very slight acidity to the water. The reported % of vinegar will be practicallyy unaffected.

Ans-3. Part A.2 and B.1:

Since the dissolved CO2 gives slight acidity to the water, but will not affect the mass of acetic acid signficantly. But it will certainly add very little acid quantity additionally in the acetic acid mass.

Ans-4. Part A.2: a. & b.

Generally the % of vinegar is reported as weight/volume and not volume/volume. The weight of vinegar gives more accurate values, otherwise we need to apply the density factor of the vinegar to get the weight indirectly from the volume measured for analysis. So, the best way is to measure the weight.The volume also gets affected by the temperature of the measurement.