Santa Monica College Chemistry 11 Name: Date: Lab Section Prelab Assignment: Eva

Question

Santa Monica College Chemistry 11 Name: Date: Lab Section Prelab Assignment: Evaluating the Cost-Effectiveness of Antacids Show all calculations clearly. A student dissolves 0.326 g of a powdered antacid in 32.36 mL of 0.1034 M HCI. The student boils the mixture and then allows it to cool. Finally, the student adds bromophenol blue indicator to the mixture, which turns yellow. 1. Calculate the total number of moles of HCl added to the antacid. 2. Boiling the mixture helps get rid of dissolved CO2. What is the source of most of this CO2? 3. Suppose that 11.72 mL of 0.1506 M NaOH is required to turn the solution from yellow to blue Calculate the total moles of OH added. Calculate the difference between the total moles of HCI added and the total moles of NaOH added 4. 5. How many moles of HCI reacted with the antacid? How many equivalents of antacid are present in the sample? Find the number of equivalents of antacid present per gram of antacid. Note that the number of moles of HCI that react with the antacid equals the number of equivalents of antacid present. 6. 7. Given that the antacid costs $5.99 per 100 tablet bottle and that the average mass of a tablet is 650 mg, calculate the cost per equivalent (in $/eq) of this antacid. Evaluating the Cost-Effectiveness of Antacids Page 1 of 1

Explanation / Answer

Q1

mol of HCl = MV = (32.36*10^-3)(0.1034) = 0.0033460 mol of HCl

Q2.

cO2 is obtained mainly from air, since it has about 0.4% of CO2 the atmosphere

Q3

mol of OH- added = MV = (0.1506)(11.72*10^-3) = 0.001765 mol of OH- added

Q4

mol of H+ - mol of OH- = 0.0033460 -0.001765 = 0.001581 mol of H+ extra

Q5

mol of H+ actually reacted = 0.001581 mol of H+ were used in the antacid

Q6.

equivalents per gram of antacid

equiv = mol/mass = 0.001581 / 0.326 = 0.00484 mol/g

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