Investigating the Effects of Surface Area on the Rate of Reaction

Data Recorded

Magnesium Ribbon – Mg + 2HCl → MgCl2 + H2

Marble Chips – CaCO3 + HCl → CaCl2 + H2O + CO2

Sodium Carbonate – Na2CO3 + 2HCl → 2NaCl + H2O + CO2

• The smallest calibration for the balance is 0.01 g. This divided by 2 equals 0.005 grams.
• The smallest calibration for the glass syringe is 5 cm3. This divided by 2 equals 2.5 cm3.
• The smallest calibration for the stop-watch is 0.01. This divided by 2 equals 0.05 s

Data Presentation

        Graphs

Processed Data

        Magnesium Ribbon Experiment

29.00±0.05+41.00±0.05+34.00±0.052=34.70 ±0.05 s

36.00±0.05+55.00±0.05+43.00±0.052=44.70 ±0.05 s

41.00±0.05+65.00±0.05+50.00±0.052=52.00 ±0.05 s

45.00±0.05+76.00±0.05+55.00±0.052=58.70±0.005 s

47.00±0.05+80.00±0.05+63.00±0.052=63.30 ±0.05 s

52.00±0.05+87.00±0.05+72.00+0.052=70.30 ±0.05 s

35.00±0.05+95.00±0.05+76.00±0.052=79.30 ±0.05 s

70.00±0.05+98.00±0.05+84.00 ±0.052=84.00 ±0.05 s

77.00±0.05+101.00±0.05+88.00±0.052=88.70 ±0.05 s

81.00±0.05+108.00±0.05+91.00±0.052=93.30 ±0.05 s

        Calcium Carbonate – The Marble Chips Experiment

29.00±0.05+27.00±0.052=28.00 ±0.05 s

43.00±0.05+45.00±0.052=44.00 ±0.05 s

52.00±0.05+61.00±0.052=56.50±0.05 s

64.00±0.05+79.00±0.052=71.5 ±0.05 s

76.00±0.05+96.00±0.052=86.00±0.05 s

91.00±0.05+110.00±0.052=100.50±0.05 s

99.00±0.05+128.00±0.052=113.50±0.05 s

110.00±0.05+143.00±0.052=126.50±0.05 s

124.00±0.05+157.00±0.052=140.50±0.05 s

128.00±0.05+171.00±0.052=149.50 ±0.05 s

136.00±0.05+187.00±0.052=161.50±0.05 s

148.00±0.05+199.00±0.052=173.50±0.05 s

156.00±0.05+213.00±0.052=184.50±0.05 s

165.00±0.05+231.00±0.052=198.00±0.05 s

177.00±0.05+243.00±0.052=210.00±0.05 s

194.00±0.05+258.00±0.052=226.00±0.05 s

208.00±0.05+273.00±0.052=240.50±0.05 s

221.00±0.05+290.00±0.052=255.50±0.05 s

231.00±0.05+304.00±0.052=267.50±0.05 s

243.00±0.05+319.00±0.052=281.00±0.05 s

        Sodium Carbonate – The Powder Experiment

3.00±0.05+2.00±0.052=2.50±0.05 s

6.00±0.05+3.00±0.052=4.50±0.05 s

13.00±0.05+5.00±0.052 =9.00±0.05 s

Conclusion

Unfortunately I was unable to create a graph using time as the independent variable, because the lab that I had utilized did not have the equipment available to accurately to record the data if time were to be the independent variable. Another factor that played into my decision was the fact that the smallest calibration of the glass syringe I used was 5 cm3. Since the only visible measurements shown on the syringe were multiples of 5, it would only seem reasonable that I switch around the variables, making time the dependent variable, and the volume collected the independent variable, since I couldn’t exactly measure how much gas would be collected every 5 seconds; otherwise the relationship the graph would depict would be completely incorrect.

As you can see on the graphs, the slightly steep slopes show when the reaction is the quickest, as it should be in the beginning. The curve shows the reaction slowing down, but unfortunately the curve continues. This is because the reaction is still taking place. I was unable to record the rest of the data because the measuring tools that were available weren’t able to record to such a high degree. In some cases though, like in the powdered sodium carbonate experiment, the reaction began so quickly that I wasn’t able to record the time in most cases, so I just stuck with those that I had managed to note down. In other cases, there were so many distractions in the lab that it was difficult to remain focused. My classmates kept removing some if the items that I was using.

The idea was to see how the rate of reaction changed when the surface area of a substance was increased. Initially, my plan was to react magnesium ribbon and magnesium powder with 1 mole of Hydrochloric acid; so I could compare and contrast how the surface area of the substance affected the rate of reaction. I had planned to keep everything about the two substances the same. Its element, mass, the amount of Hydrochloric acid I was going to react with it; the only thing different would be its surface area. Unfortunately the Lab didn’t have any available. So I decided to do the same experiment to Calcium Carbonate, this time using marble chips and powdered calcium carbonate. To my dismay I found that the powdered calcium carbonate wasn’t reacting at all. So I had to change it to sodium carbonate.

There is skepticism about using different elements, seeing as they have different orders of reactivity.  These factors, including the concentration of the acid used, could also affect the rate of reaction. However, the same acid concentration was used for all experiments, in all trials; so we can dismiss that. However, sodium is much higher up the reactivity series than calcium, which is higher up the reactivity series than magnesium. This is the problem with this experiment; the elements positions in the reactivity series could have really altered the rate of reaction.

However, the experiments still prove that when the surface area of a substance is increased, the rate of reaction increases as well. This happens because, when two substances react only the surface particles of the substances can come into direct contact with the reactant particles. Increasing a substance’s surface area, like turning big solid chunks of calcium carbonate into powder, leaves more solid particles available to react. The more particles available to react at one time, the faster the rate of the reaction.

Like this:

Only atoms on the surface can react

If you break the substance down, more

atoms are exposed and ready to react.

 

Evaluation

Considering the lack of material available, I think I was able to manage the experiment fairly enough to produce results. However, I am not pleased with the factors that may or may not have affected my results, and the circumstances in which I had to switch my variables around. Therefore I would like to state a few things I would like to alter, if ever I got the change to do this experiment again.

1. Apparatus

1. Next time, instead of using a stopwatch, I would like to use a digital device, like a laptop for example, that was somehow connected to the glass syringe, which was programmed to record the volume of the gas collected every 5 seconds. This time the graph would turn out the way it should be.
2. Instead of using a measuring cylinder, I would replace it with a burette, as it takes more accurate measurements of liquids.

2. Chemicals Used

1. I would try and used the same element next time; the only difference would be the surface area. For example, if I used magnesium, to study the effects of surface area on the rate of reaction, I would only you magnesium ribbon and magnesium powder. Studying different elements with different reactivity’s would dismiss any data already collected because an element’s position on the reactivity series may also determine the rate of reaction. Use the same element.

3. Amount of People involved in the experiment

1. If I had to do the experiment again, with the same apparatus, I think I would like to have 3 people participating in the collection of data. 1 person would be watching the syringe rise and call out to record whenever it rose, the 2nd person would time it, and the 3rd person would record it. This time, the data may be even more accurate, because no one is taking their eye off the experiment, like I was doing during my experiment just to record data.

I feel that altering these aspects of the experiment would increase the level of accuracy, as to get more substantial data to calculate the order of reaction. Unfortunately with the data I have so far, I am unable to derive the concentrations of the substances I had utilized in my experiment. However, as the objective was to investigate whether or not different surface areas affected the rate of the reaction, I think that I have produced enough data to support my theory.