The purpose of this investigation is to determine the effect varying temperatures have on the rate of reaction of magnesium (Mg) reacting with hydrochloric acid (HCl).

Apparatus:

Figure 1: Setup of Materials

Procedure:

1. Gather and setup materials as shown above in figure 1.
2. Wear safety goggles and rubber gloves to protect against hydrochloric acid (HCl)
3. Create a qualitative observation table. Headings should include qualitative properties of Magnesium strip before, during and after reaction and qualitative properties of hydrochloric acid solution before, during and after reaction
4. Create an observations table. Headings should include trial number, Temperature of HCl with uncertainty, Mass of Mg with uncertainty and Time taken for reaction to complete with uncertainty. Since there are 3 trials per condition and 5 conditions in total, there should be 15 trials listed in observations table.
5. Record qualitative observation of magnesium (Mg) and hydrochloric acid (HCl) before reaction in the qualitative observation table.
6. Using a 15cm ruler and scissors measure and cut 1.1cm of the 18cm magnesium ribbon.
7. Using the digital weight scale, measure the mass of the magnesium (Mg) strip and record the mass of magnesium strip (Mg) in table with uncertainty (±0.01g).
8. Pour 40mL of hydrochloric acid solution (HCl) into the 50±5mL Beaker.
9. Prepare the water bath, then place the 40mL hydrochloric acid solution in the 50±5mL Beaker in the water bath and set the temperature to 20°C setting on the water bath.
10. After 60 seconds (measure time using stopwatch), check the temperature of the hydrochloric acid in the 50±5mL beaker using a thermometer.
11. If the temperature is not 20°C then repeat step 7, until hydrochloric acid reaches desired temperature of 20°C.
12. When the temperature of the hydrochloric acid is near desired temperature of 20°C, record the actual temperature using thermometer in the table with uncertainty (±0.5°C).
13. Simultaneously start the stopwatch and gently drop the 1.1cm magnesium strip (Mg) into the 3.0M hydrochloric acid solution in the 50±5mL Beaker (the beaker must still remain in the water bath).
14. Record any qualitative observations that occur during the reaction of Magnesium (Mg) and hydrochloric acid (HCl) in qualitative observations table.
15. Stop the stopwatch as soon as the 1.1cm magnesium strip (Mg) completely disappears (meaning reaction is complete).
16. Record time taken for reaction to complete in observations table with uncertainty (±1s)
17. Record any qualitative observations of the hydrochloric acid solution leftover (No need for Magnesium as it had reacted fully and disappeared).
18. Turn off the water bath.
19. Take the 50±5mL beaker containing 40mL hydrochloric acid out of the water bath (NOTE: If beaker is too hot use the beaker tongs to take out the beaker).
20. Pour the hydrochloric acid down the drain with water.
21. Rinse the beaker with tap water and dry using paper towel.
22. Repeat steps 6-21 for 2 more trials of the 20°C condition of hydrochloric acid solution.
23. Repeat steps 6-22 for 30°C condition of hydrochloric acid solution.
24. Repeat steps 6-22 for 40°C condition of hydrochloric acid solution.
25. Repeat steps 6-22 for 50°C condition of hydrochloric acid solution.
26. Repeat steps 6-22 for 60°C condition of hydrochloric acid solution.
27. Clean all materials and dispose any remaining magnesium ribbon, and pour any remaining hydrochloric acid down the drain with water.

Observations:

Table 1: Qualitative Properties of HCI solution and Magnesium strip before, during and After Reaction

Table 2: Varying Temperatures of HCI, Mass of Mg strip and Time taken for reaction of Mg and HCI to complete

Analysis:

Sample Calculations:

Calculating Average Time Taken for Reaction to complete: Example for Target temperature condition 10°C

                                                Where:

x = data set of time taken for reaction to

                                complete for 10°C temperature condition                                                                n = number of trials

                        

Error Analysis:

                                                                                                                     

Calculating Moles of Mg strip: Example for all trials (since mass of magnesium strip is same for all trials)

                                                Where:

                                                        n = moles of Mg(s)

m = mass of Mg(s) strip

                                          MM = molar mass of Mg(s) strip

                                        ERROR ANALYSIS!!!!!!

Calculating Rate of Reaction: Example for target temperature condition of 10°C

                                Where:

                                                        nMg = Moles of Mg(s)

                                                        T = average time for reaction to complete for

                                10°C target temperature condition

                        ERROR ANALYSIS!!!!!!!

Table 3: Actual Temperature of HCl, Mass of Mg, Time Taken for Reaction between Mg and HCl to complete and Rate of Reaction

Figure 2: Actual temperature of HCl vs. The Rate of Reaction

*Note: Error bars represent the uncertainty of the rate of reaction

Conclusion:

        According to the observations and data obtained the hypothesis was correct. Table 2 shows that as the temperature of the glycerin increase the time taken for the marble to travel through 50mL of glycerin decreases and since viscosity is directly represented by time taken for the marble to travel through 50mL of glycerin it means that viscosity of glycerin decreases as the temperature increases. Furthermore, table 3 shows that as the temperature of glycerin increases the mean time taken for marble to travel through 50mL of glycerin decreases. Finally figure 3, illustrates that as the temperature of the glycerin increase the mean time taken for marble to travel through 50mL of glycerin decreases. Also the graph illustrates that the time taken decreases as temperature increases in an inversely proportional manner. These observations all support the hypothesis of how the higher the temperature the lower the viscosity is as by increasing the temperature of glycerin, glycerin gains more kinetic energy and is able to overcome the intermolecular forces and the molecules are now able to move around more easily and freely. This reduces the resistance between molecules and thus decreases viscosity since viscosity is the resistance of a liquid to flow. By increasing temperature of glycerin, glycerin molecules are more than likely to have enough kinetic energy to overcome the intermolecular forces between the glycerin molecules to be able to more past each other more easily, thus decreasing resistance to flow meaning as decrease in viscosity.

Evaluation:

        One source of error in this experiment was the glycerin would stick to the thermometer when the temperature was checked and as the thermometer was removed, it also pulled away some glycerin with it. This decrease the amount of glycerin there actually is and made the measurement of the glycerin inaccurate. This decreased the distance of how much the marble travels through the glycerin from 50mL. By decreasing the distance, the time taken for marble to travel through the glycerin liquid also ends up decreasing which results in an in accurate measurement of time. This causes the lower temperatures to have a lower amount of time taken for the marble to travel through the glycerin. This issue can be fixed by slightly dipping thermometer into the glycerin and making sure that only about 1 cm is in contact with glycerin. This decreases the amount of glycerin removed from graduated cylinder. Also by having larger graduated cylinder such as a 300±2.5mL, the marble could drop more easily as the diameter of the larger graduated cylinder is bigger than the smaller 100±0.5mL graduated cylinder. Furthermore, by increasing the amount of glycerin (say to 100mL for all trials) the marble travels through can help minimize the effect of losing glycerin.

        Another source of error in this experiment is that the marble touches the side of the graduated cylinder while it is traveling through the glycerin in some trials. When the marble hit the sides of the graduated cylinder it would increase the time it takes to travel through the glycerin as the sides of the cylinder would cause there to be more resistance while the marble is moving through the glycerin. This causes inaccurate measurement of time. To fix this issue, a bigger graduated cylinder with a bigger diameter (such as a 300±2.5mL) so the marble does not hit the sides of the graduated cylinder. This keeps the accuracy fairly the same as uncertainty only increases by around ±2.0mL from the original 100±0.05mL graduated cylinder and also allows the marble to travel through glycerin without hitting the sides of the graduated cylinder. Since the diameter of the marble was 2.8±0.05cm and the diameter of the 100±0.05mL graduated cylinder was 3.1±0.05cm (measured using 30±0.05cm ruler), there is only a small margin of gap between graduated cylinder and marble. Thus, by having a 300±2.5mL graduated cylinder with a diameter higher than 3.1cm it increases the gap between marble and sides of graduated cylinder and decreases the chances of the marble hitting the sides.  

References: 

Brown, C., & Ford, M. (2008). Kinetics. Chemistry: standard level : developed specifically for the IB diploma (pp. 120-123). Harlow, Essex: Heinemann International.