The questions below are based on the following "Determining ASA Mass Activity."
Step 1: crush 1 ASA tablet using a clean dry mortar and pestle. Weigh crushed tablet and determine mass is actually 0.500g
Step 2: Scrape entire crushed tablet into a flask. Rinse mortar and pestle with appx 10 ml of distilled water. Add distilled water to flask to dissolve ASA. The solution in flask may look cloudy. The ASA will dissolve but some filler may not..
Add indicator to the flask.
Use funnel, fill burette with standard NaOH (aq)
Place flask under stopcock of burette.
Add base to flask in small amounts. Swirl flask between additions of base
7. Stop adding base when indicator has changed color
8. Record volume of base used
Step 9: repeat procedure as many times as needed to have 3 consistent volumes.
Observations:
|
Trial #
|
vol of NaOH usd (ml)
|
|
1
|
18.1
|
|
2
|
17.9
|
|
3
|
12.4
|
|
4
|
18.0
|
Questions:
a) Write a balanced equation for this neutralization reaction
b) Identify 1 possible indicator that could be used in the titration. Provide an explanation for your selection
c) What volume of base will you substitute into the formula when you calculate the number of moles of base used? Provide an example
d) Calculate the number of moles and mass of ASA in one tablet. Determine the % of the original mass of the tablet that was actually ASA (percent purity of the tablet) and would give you an indication of the amount of filler that was present in the tablet.