Part B \& C: Amount of Calcium Carbonate in Antacid PART B: Preparation of Antacid Sample Pre-prepared: - 0.1MHCl - Antacid tablets crushed to a fine powder. 1. Weigh 0.4g of crushed antacid powder (record mass to 0.001g ) and place it in a clean 250 mL Erlenmeyer flask. 2. Using a clean pipet, add 40mL0.1MHCl to the powder sample (if you don't have a 40 mL pipet, use a 20mL pipet twice) 3. Boil the above mixture gently for 2 minutes to completely dissolve the powder and to get rid of as much dissolved CO2 as possible. We are not looking for a vigorous boiling. Let the mixture cool to room temperature. (There might be undissolved substances present in your solution which will be inactive ingredients such as coating / binding compounds. The active ingredients are water soluble therefore the observed undissolved matter should not affect your results) 4. Add 5-8 drops of bromophenol blue indicator to the boiled solution NOTE 1: Yellow solution indicates that your solution is acidic and green / blue solution indicates your solution is basic. If your solution doesn't turn yellow add more HCl (10 mL increments) using a pipet and note the extra volume added to your solution on your data sheet. PART C: Titration with NaOH 1. Fill a clean buret with the NaOH solution. Record your initial buret reading to the nearest 0.01mL on your data sheet. 2. Begin the titration by adding 1mL increments of NaOH while swirling your Erlenmeyer flask until your solution turns from yellow to green then finally to blue. Take precautions to avoid over titrating. Record your final buret reading on your data sheet. NOTE 2: If you overtitrate (intense blue color) you will have added too much 0.1MNaOH solution, do not start over, instead perform a back titration i.e. add enough 0.1MHCl(10mL) to make the solution acidic again (yellow color)...record the volume of the extra 0.1MHCl added. Titrate with 0.1MNaOH (buret) slowly until the solution turns blue. Record the extra 0.1MNaOH volume added