Hi! We already finished this lab for calorimetry, but I'm not sure how to complete this question. Thanks for the help!
Briefly describe the three assumptions made in carrying out this experiment. Compare your calculated enthalpy of formation of (NH4)2SO4(s) to the actual enthalpy of formation value (-1180 kJ/mol). Based on this comparison, comment as to whether or not the three assumptions are valid and comment on any potential sources of error.
These are the assumptions from the lab
"In carrying out this experiment, we were required to assume that the calorimeter used was completely insulated and prevented heat from being lost or gained (for the surroundings). We also assumed that the solution’s density and heat capacity were the same as the heat capacity (4.184𝐽/ 𝑔∙°𝐶) and density of water (1.00𝑔/𝑚L). Furthermore, it was assumed by those carrying out the experiment that the reaction took place in an open-aired environment with constant pressure conditions where the reaction vessel is not completely secured."
Now you compare the dHf you obtained with the dHf value listed as correct
and comment on how well those assumptions held up.
What is a dHf?
To compare your calculated enthalpy of formation of (NH4)2SO4(s) to the actual enthalpy of formation value (-1180 kJ/mol), you first need to understand the assumptions made in carrying out the experiment.
1. Assumption of Completely Insulated Calorimeter: This assumption means that the calorimeter used in the experiment was designed to prevent any heat loss or gain to the surroundings. It is important because it allows for accurate measurement of the heat exchanged during the reaction. If the calorimeter is not properly insulated, heat loss or gain could occur, leading to inaccurate results.
2. Assumption of Same Heat Capacity and Density: The assumption that the solution's density and heat capacity are the same as water's values (1.00 g/mL and 4.184 J/g∙°C, respectively) is made for simplification purposes. This assumption allows for easier calculations since the heat capacity and density values of water are well-known and readily available. However, it may introduce some level of error if the actual solution's properties significantly deviate from water's properties.
3. Assumption of Open-Aired Environment and Constant Pressure: This assumption implies that the reaction takes place in an environment where the pressure remains constant. It also suggests that the reaction vessel is not completely sealed or secured. This assumption allows for the simplification of the experiment and elimination of the need to measure and account for pressure changes during the reaction. However, it may introduce error if the pressure deviates significantly or if there are any changes in pressure due to gas formation or release during the reaction.
To compare your calculated enthalpy of formation to the actual value, you need to check the validity of these assumptions. If the assumptions are valid, it means they did not significantly affect the accuracy of your calculated enthalpy value. However, if any assumptions are found to be invalid, it suggests that they may have introduced sources of error.
For example, if the calorimeter used was not perfectly insulated, there could have been heat loss or gain to the surroundings, causing the calculated enthalpy value to differ from the actual value. Similarly, if the solution's properties significantly deviate from water's properties, using the assumption of identical heat capacity and density would introduce error in the calculations. Lastly, if the pressure in the reaction environment deviates significantly or changes during the reaction, it could affect the calculated enthalpy value.
In summary, to compare the calculated enthalpy value with the actual enthalpy of formation value, you need to assess the validity of the assumptions made in the experiment. Look for any potential sources of error that could have affected the accuracy of your results, keeping in mind the impact of insulation, solution properties, and pressure conditions on the measured enthalpy value.