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6-1B Factors Affecting Reaction Rate Lab

Purpose: The purpose of this lab is to investigate how  temperature, surface area and presence of a catalyst can affect the rate of chemical reactions.

Materials:  

Part 1

• two 400mL beakers (I used 250mL beakers instead)

• ice water

• hot water

• thermometer

• 3 effervescent tablets (denture cleanser tablets)

• stopwatch 

Part 2

• 3 small test tubes

• test tube rack

• dish soap

• 6% hydrogen peroxide solution

• potassium iodide

• copper(II) chloride 

• sodium chloride 

Part 3

• mortar and pestle

• sodium carbonate

• 4 small test tubes
• test tube rack

• dilute hydrochloric acid solution  

Procedure: Refer to text in BC Science 10 textbook, page 278, 279

Results:

Part 1 Effect of Temperature

Effervescent tablets in water

Temperature of water:

Ice: 4° C

Hot: 61° C 

Time for tablet to completely dissolve:

Ice water: 25:40

Hot water:   3:22

Middle temperature between 4° and 61°: 31.5°

Prediction of dissolve time: around 14:00

Actual dissolve time: 5:44

Part 2 Effect of Adding a Catalyst

Compounds in 6% hydrogen peroxide solution and dish soap

Reactant	Time	Reaction Rate
Kl	1:52	Slowest
CuCl2	1:01
NaCl	00:27	Fastest

 

Part 3 Effect of Surface Area

Materials before reaction

Sodium carbonate in dilute hydrochloric acid
Grounded powder: Faster
Lumps: Slower

Discussion:

Analyze:

1. What is the relationship between rate of reaction and change in temperature?

Increasing the temperature will increase the rate of reaction since the particles will move quicker and with more energy, leading to more collisions. Decreasing the temperature will decrease the rate of reaction. 
2. Compare you prediction in step 4 of the length of time it would take an effervescent tablet to dissolve at the middle temperature with how long it actually took. 

My prediction for the length of time was approximately 14 minutes. The way I concluded with my prediction was from calculating the middle time between how long it took for the tablet to dissolve in the hot and cold water. The actual time was 5 minutes and 44 seconds, occurring quicker than I expected.

3. (a) Which of the solutions that were added to the hydrogen peroxide solution may have acted as a catalyst? 

Potassium iodide may have acted as a catalyst because the reaction was extremely quick and the foam that contained  oxygen overflowed from the small test tube. 

     (b) Which catalyst sped up the reaction the most?

The iodine ions in potassium iodide added to the hydrogen peroxide sped up the   reaction the most. The reaction happened immediately at a very fast pace.  

 4. Which has more surface area, a 5g lump of sodium carbonate or 5 g of sodium carbonate powder?

 5 grams of sodium carbonate powder has more surface area that 5 grams lump of sodium carbonate. 

5. How did surface area affect the rate of sodium carbonate decomposition in step 14?  

The reaction of powdered sodium carbonate in dilute hydrochloric acid solution had a higher rate of reaction due to the fact that small particles have more exposed area, allowing more collisions. With sodium carbonate lumps, it had less surface area; therefore, it had a lower rate reaction. 

Conclude and Apply:

1. Suppose a reaction involved a finely grounded powder reacting with a concentrated acid.  Suggest three methods of decreasing the reaction rate.

 i) Replace finely grounded powder with lumps.
 ii) Dilute the concentrated acid by slowly adding acid to water and NOT water into acid.
 iii) Lower the temperature of the reaction. 

Conclusion:
With the three various components of this lab, I investigated and learned how temperature, surface area and catalysts can alter the rate of reaction. Each section demonstrated how reactions contrasted with each factor like low and high temperatures, greater and smaller surface areas and the presence and absence of a catalyst. 

In the future, I would be more consistent with the amount of compounds, solutions and liquids(dish soap) in each of the different experiments to achieve more accurate results. Another change would be to not rush through the lab because with the denture cleanser tablet in cold water, it was taking such a long period of time that I began to crush the tablet with an eye dropper which increased the surface area and shortened the amount of time for it to dissolve.