Reaction Rate Lab

Activity 6-2B- Factors Affecting Reaction Rate

Purpose:
To observe how various factors (temperature, surface area and the presence of a catalyst) affect the rate of chemical reactions.

Materials:

 

Part 1
• two 400 mL beakers
• ice water
• hot water
• thermometer
• 3 effervescent tablets
• stopwatch
Part 2
• 3 small test tubes
• test tube rack
• dish soap
• 6% hydrogen peroxide solution (H2
O2)
• potassium iodide (KI)
• copper(II) chloride (CuCl2)
• sodium chloride (NaCl)
Part 3
• mortar and pestle
• sodium carbonate
• 4 small test tubes
• test tube rack
• dilute hydrochloric acid solution (HCl)
Procedure:
See BC science text book, page 278-279.

Observations:

Part 1

When disolving the effervescent tablets in water, we observed a stark difference in the speed at which the tablets disolved, dependant upon the temperature of the water, as seen in the chart below. We had predicted that the tablet in 23 degree water would take over half an hour, but it was much quicker. Note that the time it took for the effervescent tablet to disolve in 5 degree water was an approximation, as keeping the water at five degrees was not possible, and we did not have enough time to observe the full reaction taking place. The line represents an estimated approximation of the relation between the rate of dissolution and the temperature of the water. (the temperature is in degrees celsius)

Part 2: Effect of a catalyst
In the second experiment we observe how a reaction between dish soap and hydrogen peroxide is affected by the presence of 3 different catalysts. The first cataylyst, copper chloride, yielded a moderate reaction, with the substance expanding to halfway up the test tube. The substance turned a bright blue, similar to the colour of the copper chloride itself.
The second catalyst, potassium iodide, was not very effective in provoking the reaction. The response to this compound was very feeble. The substance barely rose in the test tube. 
The final catalyst, sodium chloride, yielded the strongest reaction, causing a sudden, violent, rise in the level of the substance. The substance rose nearly all the way to the top of the test tube. 
All 3 test tubes can be seen in the picture below. The blue substance had copper chloride as a catalyst, the orange in the middle had sodium chloride, and the faint pink one to the far right had potasium iodide.
 

 

 

Part 3

 

The third experiment's objective was to determine the effect of surface area on a reaction between sodium carbonate and hydrochloric acid, to produce water, carbon dioxide, and table salt. First we put a chunk of sodium carbonate in a test tube with hydrochloric acid, then, in another test tube of hydrochloric acid, we put powdered sodium carbonate. In the first instance, no reaction appeared to occur. The chunk remained mostly unchanged. In the second tube however, there was a small amount of bubbling, and the powder substance in the bottom of the tube looked crystalized.

 

Discussion

Analyze

 

1) When atoms are heated, by definition they move more quickly, which makes them more likely to collide, provoking a chemical reaction. In this experiment, this was made very clear, as without heat, the effervescent tablets disolved in the water incredibly slowly. As the temperature of the water rises, the rate of reaction increases.

2) When disolving the effervescent tablet in water a temperature exactly in between the temperature of the cold water and the hot water, we predicted that it would disolve at a rate in between that of the effervescent disolved in hot water and that disolved in cold water. However, the tablet in the middle temperature was actually much closer to the rate of reaction observed in hot water. This suggests that the relationship between temperature and reaction rate in this case is exponential.

3) a and b) Sodium chloride acted as a catalyst in the reaction between the dish soap and the hydrogen peroxide, which was obvious because it provoked a much stronger reaction. Copper chloride probably also acted as a catalyst to a lesser extent, as it also provoked a reaction, though not as strong as with the sodium chloride.

4) Powdered sodium carbonate has more surface area than a chunk of sodium carbonate with the same volume.

5) The sodium carbonate in hydrochloric acid which was not crushed yielded very little reaction, but the powdered sodium carbonate yielded a full, swift reaction. More surface area lead to a quicker reaction.

 

Conclude and Apply

To make the reaction between an acid and a substance have a slower reaction, the acid should be diluted, the substance should be in a solid chunk, not powdered, and both substances should be kept cold.

 

Conclusion

 

From these experiments, I have concluded that heat, surface area, and the presence of a catalyst all increase reaction rate. To improve them, I would have observed the effervescent tablet disolving for longer, to determine exactly how long it took. I would also have used a larger variety of catalysts.