chemistry

SC156 Principles of Chemistry

Unit 6 Assignment Indigestion and Titration: An Acid-Base Titration

Imagine yourself as the lead analytical chemist at Kaplan Industries. Your first big assignment is to investigate the strength of several commercial antacids for the Food and Drug Administration (FDA). They have sent five antacids to be tested with a back-titration that works as follows:

• First, each antacid tablet is mixed with 40 mL of 0.1 M HCl—this acidic solution is the same stuff that is in stomach acid, and one antacid pill is nowhere near enough to neutralize all 40 mL of the acid.

• So, to see how much extra help each antacid pill needs to neutralize 40 mL of 0.1 M HCL, you add 0.05 M NaOH drop-by-drop to back-titrate the solution until the pH is neutral.

• What this means is that, the stronger the antacid tablet, the less NaOH it will take to help bring the acid to neutral. (In other words, the stronger antacid tablets counteract more of the original HCl, leaving the solution closer to neutral before the NaOH is added.)

Here are your results:

Based on these results, answer the following questions:

1. Which is the strongest antacid, on a single-dose basis? Which is the weakest? Explain and show your calculations.

2. Which are the strongest and weakest, on a by-weight (mass) basis?

3. When people do back titrations; they usually watch the solution for a color change when the solution becomes neutral. What might you have used in the above experiment to get this color change to happen in the solution? At what pH would the solution have been neutral?

SC156 Principles of Chemistry

4. If you had walked into the lab, only to discover that you only had 0.1 M sulfuric acid available to run your tests, how might this have affected your calculations? Why?

5. In most of the antacids you tested, the active ingredient is aluminum hydroxide. Here is an unbalanced reaction that shows how this chemical n eutralizes HCl (the main ingredient in stomach acid). Provide a balanced version of this equation:

AI(OH)3 + HCI -> AICI3 +H20

6. The FDA requires that all of its reports be super-brief — short enough so that they can be sent via text message to all of its lab sites across the country. As you probably know, the word limit for text messages is very small, so your goal here is to describe precisely what you did to test the antacids in fewer than 150 words. In this brief report, you should provide the FDA with the major findings from your tests and let them know generally how you performed your tests.

You will be required to visit the KU Science Center during any of the live tutoring sessions for review and feedback of the assignment from a KUSC tutor. This mandatory visit to the KU Science Center’s live tutoring session is worth 4 points of your grade. The KU Science Center can be accessed here: https://kucampus.kaplan.edu/MyStudies/AcademicSupportCenter/ScienceCenter/Index.aspx. Live tutoring is available Sunday 6–10 p.m. ET, Monday and Tuesday 11 a.m.–2 p.m. ET, 6–11 p.m. ET. Live tutoring can be accessed at http://www.khe2.adobeconnect.com/sciencetutor/

Use the resources in the Resource Hub for Unit 6 for help with this Assignment. Submitting Your Assignment Save your copy of the Assignment in a location and with a name that you will remember. Be sure to use the "Save As" option to include your first and last name in the title of the document. For example, your Assignment might be called Shawn_Edwards_Assignment6.doc When you are ready to submit it, click on the Dropbox and complete the steps below:

• Click the link that says “Submit an Assignment.” • In the "Submit to Basket" menu, select Unit 6: Assignment. • In the "Comments" field, include at least the title of your paper. • Click the “Add Attachments” button. • Follow the steps listed to attach your Microsoft Word document.

To view your graded work, come back to the Dropbox or go to the Gradebook after your instructor has evaluated it. Click the Dropbox to access it. Make sure that you save a copy of your submitted Assignment.