Rates of Reaction

Method:

1. Fill the first test tube with 20 ml of 0.5 M hydrochloric acid.  Fill the second with 1.0 M hydrochloric acid.  Fill the third with 2.0 M hydrochloric acid.  Label them Specimen A, B and C respectively.
2. Extract 6.0 grams of calcium bicarbonate chips.  Divide them into three equal parts (therefore, each part consisting of 2.0 grams.)
3. Simultaneously add the chips to each specimen of hydrochloric acid.  At the same time, start the stop watch.
4. A chemical reaction would begin to take place.  Make observations and record them in an observation table.
5. According to my hypothesis, Specimen C would be the first to complete the process and generate a new substance.  Record the amount of time it took to do this.
6. According to my hypothesis, Specimen B would be the second to complete the process and generate a new substance.  Record the amount of time it took to do this.
7. According to my hypothesis, Specimen A would be the last to complete the process and generate a new substance.  Record the amount of time it took to do this.
8. Write a report, comprised of your data and its implications.

Results:

Table 1: Observations

NOTE: Heat was generated and steam was therefore present.

Table 2: Conditions after 45 Minutes

Analysis:

Although, due to some human error, we were unable to complete the experiment and obtain our objective results, various observations made during the process make it possible for us to make an analysis and draw some conclusions in regards to either the confirmation or contradiction of our hypothesis.

Our observations, however, seem to support our hypothesis.  There were various indicators as to the rate of reaction of each specimen (in comparisons to one another.)  They are listed as follows:

• According to our observations the velocity/mobility of the bubbles (presumably originating from the calcium bicarbonate) was highest in Specimen C, followed by Specimens B and A respectively.  This indicates that there was the most energy or activity in Specimen C, probably as a result of the added particles (from the greater concentration) available for collision.  (Additionally, the height of foam produced instants after the two substances were combined was in this respective order: Specimen C, B and A.)
• Most apparent to us, probably, was the auditory differences between the three specimens.  Specimen C, predictably was loudest, followed by Specimens B and A respectively.  This almost designates that there was the most occurrence in Specimen C, therefore generating relatively a lot of noise.
• At forty minutes, some observations were made concerning the hue and transparency of the specimens.  It was noted that Specimen A was almost entirely clear as the majority of the bubbles initially present have disappeared.  Specimen B was partially opaque.  Specimen C, as expected, was still ‘bubbling with energy’ and opaque as a result of the seemingly unending flow of bubbles.  One could see that the chemical reaction was occurring at an extremely high pace in Specimen C, and had we been able to continue with the experiment, would have completed before both Specimens A and B.
• At the end of the period, we were able to take ‘visual measurements’ to determine whether there had been a significant reduction of the calcium bicarbonate or solute.  The clump of calcium bicarbonate was of a smaller size in Specimen C than before the initiation of the chemical reaction.  However, there had been a significant reduction in neither Specimen A nor B.
• (It may be noteworthy to add that after roughly 45 minutes, Specimen C’s temperature was slightly higher than those of Specimens A and B.  This may have been the result of greater collision of its particles, as well as higher velocity of their movements.)

Conclusion:

Our hypothesis was supported by the results obtained from the experiment.  Our observations indicated that the contents of Specimen C were reacting at a relatively high rate.  Specimen C also happened to be the most heavily concentrated sample (2.0 M.)  As I had earlier stated, when more solute had been added, there are more particles in the same volume to react with one another.  As a chemical reaction involves the collision between particles (the particles collide to generate a new substance(s)) fewer particles would mean less chance of collision.  IN SHORT: more concentration would theoretically lead to acceleration in combined substances’ rate of reaction.

Evaluation:

• There was a major human error in this experiment.  Instead of adding powdered calcium bicarbonate, we combined with our hydrochloric acid medium-sized (i.e. marble chips) calcium bicarbonate.  This, of course, possessed less surface area than the powdered kind, which caused all three specimens to require a long period of time for the completion of the chemical process.  
• Therefore, we were unfortunately unable to complete the experiment as we were not permitted to go overtime.
• This led to our failure in obtaining quantitative data.  We therefore had to make do with qualitative data and various indicators we were able to observe during the experiment, such as the mobility of the bubbles created from each specimen.

(It may be noteworthy to add that this also prevented us from being able to construct a graph.)

• (We also extracted for each specimen 2.0 grams of calcium, whilst a mere 0.5 gram would have been more suitable.)
• We were not extremely precise in our measurement of the hydrochloric acid.  Instead of the intended 20 ml we sometimes poured 19 or 21 ml.
• The stop watch was started approximately 2 – 3 seconds after the two chemicals had been combined.

Further Work:

• We could investigate the effect of temperature on the rate of reaction.
• We could investigate the effect of surface area on the rate of reaction.
• We could investigate the effect of a catalyst (such as amylase, pepsin) on the rate of reaction.
• We could investigate major factors which decrease the rate of reaction.
• We could examine the properties of various substances and make judgments concerning their rate of reaction from that.