October 2017

# Lime-A-Way

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Amiee Larchar Modic, Katy High School, Katy, Texas

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Spend 7 to 10 minutes with your group working on the assigned lab problem. During that time you should formulate an “answer” to the proposed questions and be prepared to explain and justify your answer to other groups. Lime-A-Way® is a liquid household product used to “dissolve away hard water mineral build-up on contact.” It contains a strong monoprotic acid, which we will call HA. You also have two different white powders labeled A and B; one is baking soda (NaHCO3, 84.01 g/mol), and one is washing soda (Na2CO3, 105.99 g/mol). The materials listed are available for your use.

## Materials List

- balance (±0.01 g)
- weighing boat
- 6-well reaction plate
- spatula
- 2 thin stem pipettes
- goggles
- apron
- 10-mL graduated cylinder

## Chemical List

- bottle of distilled water
- 1 dropper bottle of Methyl Red (below pH 4.4 red – above pH 6.2 yellow)
- 100 mL beaker with 30 mL of Lime-A-Way
- 2 vials of white powder, labeled A and B. (one with baking soda, one with washing soda)

1. Write the equations for the reactions between the Lime-A-Way and the powders.
   1. With baking soda:_______________________________
   2. With washing soda: _____________________________
2. Explain how you would use Lime-A-Way to determine which powder is baking soda and which is washing soda.
3. Write a brief procedure outlining the steps you would take to determine the concentration of the acid in the Lime-A-Way.
4. Briefly list or explain each of the following:
   1. The measurements that will be needed.
   2. The calculations that will be needed. (show the set up for the calculations)
   3. How you will determine the volume of the Lime-A-Way used.
   4. What color change you will look for and why.

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