How To Write A Lab Report Calorimetry

Thermochemistry

Saxon Evans
& Zac Taylor
Dr. Nachman
2/08/2011
Abstract: Using the chemical equation we can study the reaction taking place between magnesium metal and sulfuric acid in solution. The = for the reaction of sulfuric acid and magnesium metal.

Introduction
This report demonstrates calorimetry, or the technique of measuring heat effects in the surroundings. In order to make sure that there is no temperature change, or that it is an isothermal heat transfer, it is kept at a similar temperature in an ice bath. By knowing the change in volume, the density of ice, and the density of liquid water, it is presumed that then you could decipher the mass of the ice that melted. With this, it is possible to understand the transfer of heat from this chemical equation to its surroundings. As the chemical reaction gives off heat and energy to its surroundings, it is an endothermic reaction. This means that it will have a positive change in H.

Methods
First, test the calorimeter apparatus to make sure that it is working properly without any substantial leaks. Then, fill the calorimeter with crushed ice, and cool water till it is full to the brim. Then, place the
seal on top so that there is no excess air in the instrument. Place apparatus into an ice bucket to ensure that there is no unnecessary heat escaping throughout the procedure. Make sure once again that there are no leaks and that it is ready to go. Start recording the time and volume of water. Now combine the magnesium (which I used 0.2409 g) metal with the sulfuric acid (5ml). Continue recording the volume of water every thirty seconds. After around fifteen minutes, the chemical equation subsides.

Data:
Table 1. Ice Calorimeter data for first experiment (using 0.2448 g of magnesium). Time (s) | Pipette (mL) | 0 | 0.921 | 30 | 0.850 | 60 | 0.765 | 90 | 0.684 | 120 | 0.619 | 150 | 0.566 | 180 | 0.521 | 210 | 0.483 | 240 | 0.453 | 270 | 0.429 | 300 | 0.408 | 330 | 0.389 | 360 | 0.370 |

Table 2. Ice Calorimeter data for second experiment (using 0.2409g of magnesium). time(s) | pipette (mL) | 0 | 0.908 | 30 | 0.878 | 60 | 0.869 | 90 | 0.853 | 120 | 0.837 | 150 | 0.824 | 180 | 0.809 | 210 | 0.794 | 240 | 0.781 | 270 | 0.769 | 300 | 0.758 | 330 | 0.756 | 360 | 0.798 | 390 | 0.82 | 420 | 0.848 | 450 | 0.823 | 480 | 0.82 | 510 | 0.813 | 540 | 0.804 | 570 | 0.799 | 600 | 0.789 | 630 | 0.774 | 660 | 0.765 | 690 | 0.756 | 720 | 0.748 | 750 | 0.738 | 780 | 0.728 | 810 | 0.718 | 840 | 0.708 | 870 | 0.698 | 900 | 0.688 | 930 | 0.678 | 960 | 0.671 | 990 | 0.668 | 1020 | 0.651 |

Table 2. Ice calorimeter data time(s) | pipette (mL) | | | | 0 | 0.875 | | | | 30 | 0.872 | | | | 60 | 0.870 | | | | 90 | 0.870 | | | | 120 | 0.869 | | | | 150 | 0.868 | | | | 180 | 0.866 | | | | 210 | 0.863 | | | | 240 | 0.863 | | | | 270 | 0.861 | | | | 300 | 0.861 | | | | 330 | 0.860 | | | | 360 | 0.860 | Add H2SO4 | | | 390 | 0.760 | | | | 420 | 0.656 | | | | 450 | 0.575 | | | | 480 | 0.516 | | | | 510 | 0.468 | | | | 540 | 0.432 | | | | 570 | 0.402 | | | | 600 | 0.387 | | | | 630 | 0.368 | | | | 660 | 0.350 | | | | 690 | 0.342 | | | | 720 | 0.330 | | | | 750 | 0.328 | | | | 780 | 0.321 | | | | 810 | 0.320 | | | | 840 | 0.318 | | | | 870 | 0.318 | | | | 900 | 0.318 | | | | 930 | 0.318 | | | | 960 | 0.318 | | | | Data collected 2011.01.24 by --- and --- |

Calculations

The =0.536, =0.524, and =0.542.
The Masses of ice melt can then be determined as follows:

0.524 mL melt x 1g ice/.0918mLmelt= 5.71 g ice min
0.536 mL melt x 1g ice/.0918mLmelt= 5.84 g ice avg
0.542 mL melt x 1g ice/.0918mLmelt= 5.90 g ice max

An estimate of the heat energy released by the energy is:

5.71 g x = 1.91 kJ min
5.84 g x = 1.95 kJ avg
5.90 g x = 1.97 kJ max
Determining the limiting reagent:

.25 g Mg x = 10.29 mmol Mg available

5.00 mL solution x =5.00 mmol available

Now that we know that Sulfuric Acid is the limiting reagent, we can calculate the experiment molar enthalpy:

= 382 kJ/mol

=390 kJ/mol

=394 kJ/mol

The experimental = for the reaction of sulfuric acid and magnesium metal. This compares with an expected value of –466.9 kJ/mol at 25°C.

Analysis of Uncertainty
After first two times that my partner and I went through the lab, there were still huge margins of human error.
The first time, the two of us did not go long enough in order to see the upward curve signifying the end of the chemical reaction. The second time, the results were taken long enough to show a slow stop of the reaction, but it was still had error. There had been no ice put into the apparatus, so it was impossible to accurately record the correct change in volume due to the heat of the reaction. After these two inadequate attempts, we are now using sample data to show the correct process and results. Also, there could have been heat escaping from the experiment the whole time we were recording data, especially as the chemical reaction was underway. This could ruin the
results.

Reference:

Darrell D. Ebbing , Steven D. Gammon, General Chemistry, 9th ed., Houghton Mifflin, Boston, 2009.

“Appendix C: Thermodynamic Quantities for Substances and Ions at 25°C” in Darrell D. Ebbing, Steven D. Gammon, General Chemistry, 9th ed., Houghton Mifflin, Boston, 2009.