Cal Lab Report

Calorimetry: Determination of Heats of Solution ##-##-2022 By: #### Lab Section: L3 TA: Procedure: Calibrating the Calorimeter 1. 60mL of distilled water was heated in an 250mL beaker on a hot plate. The water was heated to 75 ⁰ C. 2. 15.0 mL of distilled water at room temperature was measured into the calorimeter using a 50 mL graduated cylinder. 3. The calorimeter was then sealed and shaken for 60 seconds. The temperature was taken. 4. 20.0 mL of hot water was measured into the calorimeter using a 50 mL graduated cylinder after taking the temperature of the hot water. 5. The calorimeter was then sealed and shaken for 60 seconds. The temperature was taken. 6. The calorimeter was rinsed with distilled water before being dried using a tissue. The process was repeated 2 additional times. Heat of Solutions 7. 35.0 mL of room temperature distilled water was measured into the calorimeter using a 50mL graduated cylinder. 8. The calorimeter was then sealed and shaken for 60 seconds. The temperature was taken. 9. 1.5g of anhydrous sodium acetate was measured using an analytical balance. It was then poured into the calorimeter. 10. The calorimeter was then sealed and shaken for 60 seconds. The temperature was taken. 11. The calorimeter was rinsed with distilled water before being dried using a tissue. The process was repeated 3 addition times using 2.0g, 2.5g, and 3.0g of anhydrous sodium acetate. 12. The process was then repeated 4 addition times using 1.5g, 2.0g, 2.5g, and 3.0g of sodium acetate trihydrate. Data and Observations:

Table 1: Theoretical Molar Heat Compound Theoretical Molar Heat (kJ/mol) NaC 2 H 3 O 2 -17.32 NaC 2 H 3 O 2 •3H 2 O +19.66 Table 2: Temperatures of distilled water used to calibrate the calorimeter Trial Volume of Cold Water (mL) Volume of Hot Water (mL) T 1 (± 0.2 ⁰ C) T 2 (± 0.2 ⁰ C) T f (± 0.2 ⁰ C) 1 15.0 20.0 19.1 55.4 34.5 2 15.0 20.0 20.0 57.0 37.8 3 15.0 20.0 20.1 57.0 34.8 Table 3: Change in temperature per mass of water Trial Mass of cold water (g) Mass of warm water (g) ΔT of Cold Water ( ⁰ C) ΔT of Warm Water ( ⁰ C) 1 15.0 20.0 15.4 -20.9 2 15.0 20.0 17.8 -19.2 3 15.0 20.0 14.7 -22.2 Table 4: Initial and final temperature for sodium acetate anhydrous dissolved in water Trial Mass (± 0.02g) Initial Temperature (± 0.2 ⁰ C) Final Temperature (± 0.2 ⁰ C) 1 1.50 20.0 21.6 2 2.01 19.1 22.0 3 2.50 19.5 22.8 4 3.03 19.5 23.5 Table 5: Change in temperature once turned into solution Trial Mass (± 0.02g) ΔT ( ⁰ C) Mass of Solution (g) 1 1.50 1.6 36.50 2 2.01 2.9 37.01 3 2.50 3.3 37.50 4 3.03 4.0 38.03

Calculations: 1. Calculating the heat capacity of the calorimeter: C cal = − [ ( m cool water ) ( ρ water ) ( ∆T cool water ) + ( m warmwater ) ( ρ water ) ( ∆T warmwater ) ] ∆T calorimeter / cool water C calT 1 = − [ ( 15.0 ) ( 4.184 ) ( 15.4 ) + ( 20.0 ) ( 4.184 ) ( − 20.9 ) ] 15.4 C calT 1 = 50.806 J / °C C calT 2 = − [ ( 15.0 ) ( 4.184 ) ( 17.8 ) + ( 20.0 ) ( 4.184 ) ( − 19.2 ) ] 17.8 C calT 1 = 27.502 J / °C C calT 3 = − [ ( 15.0 ) ( 4.184 ) ( 14.7 ) + ( 20.0 ) ( 4.184 ) ( − 22.2 ) ] 14.7 C calT 3 = 63.614 J / ° C C calav = ∑ C cali n C calav = 50.806 + 27.502 + 63.614 3 C calav = 47.307 J / °C 2. Calculating the molar heat for each mass: ∆ H soln = m ∗ c ∗ ∆T n solute ∆ H solnT 1 = ( 36.51 × 10 − 3 ) ∗ 4.184 ∗ ( − 1.6 ) ( 1.51 82.03 ) ∆ H solnT 1 =− 13.578 kJ / mol

Molar heat of solution of sodium acetate anhydrous Trial Mass (± 0.02g) Moles Mass of Solution (g) ΔH of Solution (kJ/mol) 1 1.50 0.018 36.50 -13.6 2 2.01 0.025 37.01 -18.0 3 2.50 0.030 37.50 -17.3 4 3.03 0.037 38.03 -17.2 Molar heat of solution of sodium acetate trihydrate Trial Mass (± 0.02g) Moles Mass of Solution (g) ΔH of Solution (kJ/mol) 1 1.51 0.01110 36.51 22.0 2 2.01 0.01478 37.01 21.0 3 2.52 0.01838 37.52 18.0 4 3.05 0.02228 38.05 21.4 3. Calculating average value for molar heats: ∆ H av = ∑ ∆ H i n ∆ H 1 av = ( − 13.578 ) + ( − 17.963 ) + ( − 17.259 ) +(− 17.202 ) 4 ∆ H av =− 16.501 kJ / mol ∆ H 2 av = ( 22.019 ) + ( 20.954 ) + ( 17.927 ) +( 21.425 ) 4 ∆ H av = 20.581 kJ / mol Precision = ∆ H high − ∆ H low ∆H av × 1000

value of -17.32 kJ/mol. This level of error means that the calculated value is consistent with the theoretical value. The average molar heat for sodium acetate trihydrate is 20.6 kJ/mol, making it an endothermic reaction. The precision and relative error were calculated to be 199 ppt and 4.68%, respectively. Once again, this level of error means that the average value is consistent with the theoretical. The heat capacity of the calorimeter was calculated to be 47.3 J/ ⁰ C