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Ammonium Chloride Enthalpy Lab. Data Collection and Processing

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Introduction

Determining ?H Experimentally Data Collection and Processing Trial # Mass of water (g � 0.01g) Mass of NH4Cl (g � 0.01g) Initial Temperature of water (oC � 0.05 oC) Final Temperature of Solution (oC � 0.05 oC) Change in Temperature (oC � 0.10 oC) 1 23.40 g 3.50 g 16 oC 7oC 9oC 2 24.78 g 3.40 g 23oC 16oC 7oC 3 23.37 g 3.51 g 31oC 22oC 9oC 4 24.05 g 3.49 g 13oC 6oC 7oC Calculations Information Used: Specific Heat Capacity of Water = 4.186J/g oC Specific Heat Capacity of NH4Cl = 3.95J/g oC Trial 1: Step 1: Calculate Moles of NH4Cl (Mass / Molar Mass) = (3.50 � 0.01 / 53.49) = (3.50 � 0.28% / 53.49) = 0.07 � 0.0002 moles Step 2: Calculate the enthalpy change Q = n x ?H Q = energy from water -Q = energy transferred from water ?H = - Q / n ?H = - [(23.40 � 0.01)(4.186)(( 7 � 0.05) ...read more.

Middle

/ 0.06 � 0.29%] = -( -13830.50 � 1.76%) = 13830.50 J/mol � 243.42 J/mol Trial 3: Step 1: Calculate Moles of NH4Cl (Mass / Molar Mass) = (3.51 � 0.01 / 53.49) = (3.51 � 0.28% / 53.49) = 0.07 � 0.28% = 0.07 � 0.0002 moles Step 2: Calculate the heat (enthalpy) change Q = n x ?H q = energy from water -q = energy transferred from water ?H = - Q / n ?H = - [(23.37 � 0.01)(4.186)(-9 � 0.1)] / 0.07 � 0.0002 = - [(23.37 � 0.04%)(4.186)(-9 � 1.11%)] / 0.07 � 0.28% = - [ (-880.44 � 1.15%) / 0.07 � 0.28%] = -( -12577.73 � 1.43%) = 12577.73 J/mol � 179.86 J/mol Trial 4: Step 1: Calculate Moles of NH4Cl (Mass / Molar Mass) = (3.49 � 0.01 / 53.49) ...read more.

Conclusion

Firstly,the Styrofoam cup we used as a calorimeter absorbed some of the heat, however this was not reflected in the calculations. Also, the coffee cup lid we used was not effective in isolating the system, so heat was lost to the surroundings. When we opened the lid to add the Ammonium Chloride, we left it open for a short time, during which the energy was not retained within the calorimeter. If the lid was made with no holes, except for the thermometer, less heat would leak out. Another large problem was the way we mixed the Ammonium Chloride into the water. We shook the calorimeter from side to side, but by doing this we inadvertently added extra momentum and therefore heat to the system. In addition, the temperature of the room was not monitored, so the temperature of the environment could have been changing, which would affect the reaction. We could remedy this by ensuring the temperature stayed at standard room temperature the entire time the reaction was taking place. ...read more.

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