My PBL Project

pH rainbow

Question

How can you measure acidity using the pH rainbow tube?

Design/Plan

What we will be doing in our project is add a saturated sodium carbonate solution to a test tube containing a dilute solution of hydrochloric acid and use an universal indicator. We will be observing a rainbow of colors develope in the tube as the dense sodium carbonate sinks to the bottom, of the test tube, and carbonate ions diffuse upward and neutralize the acid.

Investigation

What we will be doing in our project is add a saturated sodium carbonate solution to a test tube containing a dilute solution of hydrochloric acid and use an universal indicator. We will be observing a rainbow of colors develope in the tube as the dense sodium carbonate sinks to the bottom, of the test tube, and carbonate ions diffuse upward and neutralize the acid.

To see the density of sodium carbonate sink as it sinks to the bottom, of the test tube, and carbonate ions diffuse upward and neutralize the acid.

Purpose

The purpose of us doing this experiment is to create a pH rainbow tube, where after we will figure out how to apply it into a real- world situation.

Materials

-Test tubes, large 20x150 mm

-Test tube racK

-Beral-type pipet,

-Hydrochloric acid solution, 0.1M ,20mL

-Sodium carbonate, saturated, 6mL

-Universal indicator, 3mL

Procedure

1.Add about 3 mL of universal indicator solution and 20 mL of hydrochloric acid solution to a large test tube. Swirl the test tube to mix. This should produce a bright red color.

2. Fill a Beral-type pipet with sodium carbonate solution. (This is approximately 3 mL)

3. Tilt the test tube slightly and slowly squeeze the sodium carbonate solution down the side of the test tube to the bottom. The sodium carbonate solution will sink to the bottom of the test tube. Refill the pipet with more sodium carbonate and add to the test tube in the same way. (Total amount of sodium carbonate added is 6 mL)

4.Place the test tube on the test tube rack and observe the changes.

5. Colored layers form gradually resulting in a rainbow spectrum of colored layers in the tube that will remain for several days if left undisturbed.

Safety

Dilute hydrochloric acid and saturated sodium carbonate solutions are skin and eye irritants. Avoid contact of all chemicals with eyes and skin. Universal indicator solution is alcohol-based and is therefore inflammable. Keep away from flames and other ignition sources. Wear chemical splash goggles, chemical-resistant gloves, and a chemical-resistant apron. Review current Material Safety Data Sheets for additional safety, handling, and disposal information. Dispose of materials correctly.

Data

pH tested with litmus paper

HCl- 0-1 on pH scale very acidic

Na2CO3- 10-11 On pH scale- very basic

Calculations

Compare Litmus paper color change to color on the tube to determine pH number.

Analysis and Conclusion

The dense sodium carbonate sinks to the bottom, of the test tube, and carbonate ions diffuse upward and neutralize the acid.

Application and Extension

We learned that there are different pH's for different substance and the affects of pH neutralization occur