Take Home Lab #10

Take Home Lab #10: Reaction Rate

Question: What affects the speed at which a chemical reaction occurs (reaction rate)?

Safety: Hot water should come from the tap, not from the microwave or stove. Use caution even with hot tap water. Clean up any spills immediately.

Materials: Alka-Seltzer or other effervescent table, water

Procedure: There are several factors that affect the speed of a chemical reaction or reaction rate. In this lab, you will use Alka-Seltzer tablets to start a chemical reaction and then take several steps to adjust the reaction rate. Alka-Seltzer tablets have several acids (citric, ascorbic, etc) and a base (sodium biocarbonate) in them. When they are dissolved in water, these chemicals react and make carbon dioxide bubbles as well as several other products. You will time how long it takes for a piece of the Alka-Seltzer to completely react to determine the reaction rate.

            Cut your Alka-Seltzer tablet into four pieces. If it breaks apart a little, that’s OK: just keep the smaller pieces together. You will need to have four cups of water ready, two cold temperatures and two hot (not boiling, but hot water from the tap) cups of water. Be ready to time how long it takes for each piece of Alka-Seltzer to react. In the first cup of cold water, add one piece of Alka-Seltzer tablet and time how long it takes to react completely. Next, crush up the 2nd piece of tablet and add it to the second cup with cold water. For the third cup, add the a 3^rd piece to the hot water. For the last cup, crush the 4^th piece of tablet and add it to the hot water.

           

Data:

Create your own data chart to record how long it took for each sample to react completely, as well as any other observations that you made.

Post-Lab Questions:

1. Write out your data table and observations for all four trials.

2. Which reacted faster, cup 1 or cup 2? Cup 3 or cup 4?

3. Which reacted faster, cup 1 or cup 3? Cup 2 or cup 4?

4. How do each of the following factors change reaction rate (for example, make it faster or slower): cold water, hot water, crushing the tablet?

5. A company that makes flavored water is having trouble getting all of the natural flavorings to dissolve quickly. What would you recommend they do to make the process faster? Explain.