Mapúa UniversitySenior High SchoolScience, Technology, Engineeringand MathematicsExperiment 5
Factors Affecting Rate of Chemical Reaction
Gasataya, Guinto, Olais, Saavedra November 20, 2018
Ms. Hazel Jean Soriano Group 3 – CHM02 – IS204
In this experiment, the objective is to show the effects of the different factors affecting the rate of chemical reaction. The researchers tested 4 main factors that affect the rate of reaction. Each factor has a corresponding procedure, for the first factor, chemicals were mixed in two separate test tubes and was observed until there were appearance of bubbles. Same goes for the second factor but this time, the test tubes were immersed in a water bath with 3 different temperatures. In the third factor, time was measured by which test tube showed bubbles first. The last factor has the same process as the first, but with different chemicals. The researchers then found the rate was inversely proportional to the temperature and to the concentration. The same goes for the nature of the reactants and the presence of a catalyst.
The study about the rates of chemical reaction and the mechanism by which a reaction can take place is called Chemical Kinetics. The rate of reaction is the change in concentration of the reactant or the product in a given period of time. This experiment discussed the main factors that affect the rate of reaction, namely the nature of the reactants which is the physical state of the reacting species, the concentration which helps increase the chances of molecules to collide with one another, the temperature which implies higher kinetic energy to create more collision, and the catalyst which speeds up the rate of reaction. With that, the objective to demonstrate the effects of the different factors to the rate of concentration can be obtained.
In this experiment equipment used are micro test tubes, 150mL beaker, and medicine dropper.
For the effect of the nature of the reactants to the reaction rate, the students placed 1mL of 1M hydrochloric acid, HCl, into each of the 2 micro test tubes. Half a gram of aluminum turnings was added to one of the test tubes, while iron fillings of the same amount was added to the other. The appearance of bubbles and its rate was then observed and compared. For the effect of the temperature, on the other hand, the students placed 3 drops of 0.15M sodium thiosulfate in test tube 1 and 3 drops of 3M hydrochloric acid, HCl, and water drops for test tube 2. A 150-mL beaker was filled with 100mL of tap water where the 2 micro test tubes were immersed for a water bath in the span of 3 minutes. The temperature of the tap water was measured, and a piece of paper was marked with an X. The content of micro test tube 2 was poured into micro test tube 1 as it was held above the marking on the paper. The time it took until the X was no longer visible was recorded. This process was repeated twice for different temperatures; one was 20oC higher than room temperature while the other was 40oC higher. The next observation was for the effect of concentration, the students placed 1 mL of hydrochloric acid, HCl, into each of the three micro test tubes. Each of the micro test tubes contained HCl of different concentrations, 0.5M, 1M, and 1.5M. A 1-cm magnesium ribbon strip was then dropped into the micro test tubes and the time was recorded. Lastly, for the effect of the catalyst, 15 drops of 10% hydrogen peroxide was placed into each of the two micro test tubes. Three drops of 1M cupric sulfate was then added to one of the test tubes and the appearance of bubbles in the 2 micro test tubes was observed while the rates of the reactions were compared.
Results and Discussion
The experiment about factors affecting the rate of chemical reaction was divided into four different parts — effect of nature reactants to the reaction rate, effect of temperature to the reaction rate, effect of concentration to the reaction rate, and effect of catalyst to the reaction rate.
The first part was determining the effect of nature of the reactants to the reaction rate. In order to accomplish the experiment, two micro test tubes, one filled with mixture of Hydrochloric Acid and Aluminum turnings (2Al + 6HCl 2AlCl? + 3H?), and the other one filled with mixture of Hydrochloric Acid and Iron Fillings (2Fe + 6HCl ? 2FeCl? + 3H?); were observed to see which of the aluminum turnings and the iron fillings would react first along with the Hydrochloric acid. Factor such as bubble in the substance was considered to be able to determine which of the two samples is more reactive. Due to this factor, it has been observed that the aluminum turnings have a faster rate of reaction for it was the first one to have bubbled, and its temperature seemed to be higher than of the Hydrochloric acid and iron fillings. Implications of the observation was explained by the activity series of metal. Activity series or reactivity series of metal shows if a certain metal is highly reactive or not with it being grouped as reactive with water as highly reactive, followed by reactive with acids, and the highly unreactive group. Aluminum and iron are both in the reactive with acids group, but aluminum is in the higher part of the hierarchy, which explains why it reacts more with hydrochloric acid.
The next part was determining the effect of temperature to the reaction rate. In order to accomplish the experiment, two micro test tubes, one filled with three drops of 0.15M sodium thiosulfate (marked as number 1), and the other one filled with three drops of 3M hydrochloric acid and drops of distilled water (marked as number 2); were immersed in a water bath for 3 minutes, mixed together, and was observed to see how fast the reaction will occur — it was done 3 times in different temperatures, but with constant duration of time to see if the reaction varies along with the temperature into which the substance was exposed. Table 1 shows the values obtained from the 3 trials.
TEMPERATURE(°C) TIME (in seconds) TO COMPLETE THE REACTION
At room temperature (T1) 110 seconds
T1 + 20°C 53 seconds
T1 + 40°C 43. 77 seconds
To be able to accurately know if the reaction has completely occurred, an “X” mark was drawn in a blank sheet of paper and for each trial the mixture of the substance 1 & 2 was placed on the top of the mark and was observed; when the “X” mark has completely disappeared, the time was noted. After the trials were done, it was observed that the higher the temperature the substance was exposed, the faster the reaction occurs. Therefore, trial 3 which is at 40°C, has the fastest rate of reaction.
The third part was determining the effect of concentration to the reaction rate. In order to accomplish the experiment, three micro test tubes were filled with 1mL of hydrochloric acid (HCl), but with different concentrations, one at 0.5M hydrochloric acid (HCl), another one at 1M hydrochloric acid (HCl), and the other at 1.5M hydrochloric acid (HCl); were observed after a 1-cm strip of magnesium ribbon was added to each sample. Table 2 shows the obtained values for each sample.
HCl concentration Time in seconds to complete the reaction
0.5M 3.01 seconds
To be able to determine how fast the reaction will be for each sample, 1-cm of magnesium ribbon was added to each micro test tubes containing hydrochloric acid at different concentrations and was timed for how long before the magnesium ribbon will react with the hydrochloric acid. Appearance of bubbles was used as an indicator if the reaction has already occurred. After placing the magnesium ribbon to each sample, it was observed that the higher the concentration of the hydrochloric acid, the faster the reaction will be. Therefore, hydrochloric acid at 1.5M has the fastest rate of reaction with it reacting for as fast as 1.14 seconds.
The last part was determining the effect of catalyst to the reaction rate. In order to accomplish the experiment, two micro test tubes were filled with 15 drops of hydrogen peroxide at 10 percent. One of the test tubes was pure hydrogen peroxide, and 3 drops of 1M cupric sulfate was added to the other. To be able to compare the rate of reaction between the two samples, appearance of bubbles was, again, used as an indicator. In this experiment, cupric sulfate acts as a catalyst, so it should speed up the reaction. But upon the observation during the performed experiment, it seemed to be that the one without the cupric sulfate has reacted more than the ones with it because bubbles were more apparent in it. The concentration of the catalyst must have affected the rate of reaction. The concentration of the catalyst may not be enough to speed up the rate of reaction. Though, the appearance of so much bubbles in the hydrogen peroxide without the catalyst, might be an indication that it was exposed in a certain condition like high temperature or sunlight, making it decompose even without the help of the catalyst.
Several conclusions were made in the conducted experiment. Firstly, it was concluded that higher temperatures cause faster reactions and that the rate was inversely proportional to the temperature. Secondly, the rate was also inversely proportional to the concentration as higher concentrations lead also faster reactions. The same goes for the nature of the reactants and the presence of a catalyst. The rates of reaction vary from one different reactant to another and the presence of a catalyst also speeds up the reaction.