Fundamentals of Calorimetry Lab Report Dr Z Edits

Data Table 2a: For C w use 4.18 J/g∙ ℃ Calculation #     5g CaCl 2   10g  CaCl 2   15g  CaCl 2   Mass of water (g) m w     100 g    100 g    100 g Mass of salt (g)  m s    5.01 g    10.07 g    15.08 g 9 Moles of salt solution ( m s x mol/g)     .045 moles of CaCl2    .091 moles of CaCl2    .136 moles of CaCl2 Initial Temperature,  T i   (°C)     17 °C    17 °C  16.5 °C   Final Temperature,  T f (°C)    22 °C      30 °C    40 °C 10 Change in Temperature (°C)    ∆T  = T f  - T i    5 °C      13 °C  23.5 °C   11 Heat absorbed by the solution (J)  q w  = - [c w  x m w  x ∆T ]  -2090 J    -5434 J     -9823 J 8 Average Heat Capacity of the Calorimeter,   C AVE . From Data Table 1B   41.08 J/°C 41.08 J/°C 41.08 J/°C 12 Heat absorbed by the calorimeter (J)  q c  =  - [ C AVE  x  ∆T ]   -205.4 J      -534.04 J  -965.38 J   13 Enthalpy of solution (J)  ∆H =  q w  +  q c      -2295.4 J  -5968.04 J    -10788.38 J   14 ∆H ( Enthalpy of solution) in kJ  *Note: 1 kJ = 1000 J     -2.2954 kJ    -5.968045 kJ    -10.78838 kJ 15 ∆H/moles of salt  Enthalpy per mole of solution in kJ/mol    -51.01 kJ/mol CaCl2  -65.58 kJ/mol CaCl2      -79.33 kJ/mol Cacl2 ©2016 2 Carolina Biological Supply Company

19 Heat absorbed by the calorimeter (J)  q c  =  - [ C AVE  x  ∆T ]    -328.64 J  -287.56 J    -431.34 J 20 Enthalpy of solution (J)  ∆H =  q w  +  q c    3015.36 J    2638.44 J    3957.66 J   21 ∆H ( Enthalpy of solution) in kJ  *Note: 1 kJ = 1000 J     3.01536 kJ    2.63844 kJ    3.95766 kJ 22 ∆H/moles of salt  Enthalpy per mole of solution in kJ/mol    32.08 kJ/mol NH4Cl    14.11 kJ/mol NH4Cl    14.03 kJ/mol NH4Cl NH 4 Cl Work: ©2016 2 Carolina Biological Supply Company

Question 3: What sort of relationship exists between the temperature change and the mass of the solid? Explain why that relationship exists. Hint: See your lab manual Background. I learned from our lab manual this week that enthalpy is dependent on the amount of substance present, and that heat or heat energy measures the amount of energy a sample contains (2015). Additionally, heat energy is an extensive property that is dependent on mass (2015). For example, even if a gallon and a drop of heated water both have a temperature of 100 °C, the gallon has a much higher heat energy simply because there is more of it (2015).   Question 4: How do the calculated molar heats (∆H/moles of salt) of solution for calcium chloride compare to one another? How do the calculated molar heats of solution for ammonium chloride compare to one another? Hint: Compare the values of the determined Enthalpy/mole of solution for each compound at the different masses. Are they similar? How similar? Did the values you determine differ a lot? A little? Include numerical information in your response. Even though the masses of CaCl2 varied substantially during each trial, ranging from 5.01 grams of CaCl2 to 10.07 grams of CaCl2, the molar heats of solution for calcium chloride were relatively similar. The molar heat at the mass of 5.01 grams for CaCl2 was -51.01 kJ/mol CaCl2, the molar heat at the mass of 10.07 grams CaCl2 was -65.59 kJ/mol CaCl2, and the heaviest mass of 15.08 grams of CaCl2 was -79.33 kJ/mol CaCl2. Each of the molar masses of CaCl2 increased by approximately 14 kJ/mol (give or take a little) with each weight increase. As for NH4Cl, the kJ/mol moved in the opposite direction and became smaller as the amount of NH4Cl increased. At 5.01 grams of NH4Cl, the calculated molar heat of solution for ammonium chloride was 32.08 kJ/mol NH4Cl, whereas at 10.02 grams and 15.06 grams of NH4Cl, the corresponding calculated molar heats were 14.11 kJ/mol NH4Cl and 14.03 kJ/mol NH4Cl. I was somewhat surprised by the results of the NH4Cl calculated molar heats, since the heavier masses (10.02 grams and 15.06 grams of NH4Cl) had very similar calculated molar masses (14.11 kJ/mol NH4Cl and 14.03 kJ/mol NH4Cl), but the lightest mass, 5.01 grams of NH4Cl, differed significantly with a calculated molar mass of 32.08 kJ/mol NH4Cl. This could be due to human error on my part, or be attributed to using a different bottle of water (with a slightly warmer base temperature) for the trials conducted with larger amounts of NH4Cl. Question 5: The actual molar enthalpy of solution (∆H/moles of salt) for calcium chloride is -81.3 kJ/mol, whereas the molar enthalpy of solution of ammonium chloride is 14.8 kJ/mol. Calculate the average molar enthalpy of solution for each compound based on your data, and then calculate the percentage error for calcium chloride and ammonium chloride using your calculated average.  Do not calculate the percent error for each mass. 1.) Average molar enthalpy of solution for ammonium chloride: 20.07 kJ/mol NH4Cl 2.) Average molar enthalpy of solution for calcium chloride: -65.31 kJ/mol CaCl2 ©2016 2 Carolina Biological Supply Company

Carolina Biological Supply Company . (2015). CHM 101L M4 Fundamentals of Calorimetry Investigation Manual . Vedantu . (2020, July 21). Q + A . Vedantu. https://www.vedantu.com/question-answer/calorimeters-are- generally-made-up-of-acopper-class-11-physics-cbse-5f16e7f63242933b530b78a7 ©2016 2 Carolina Biological Supply Company