The purpose should be several well constructed sentences that include a majority of the topics covered in this experiment. These topics can be both conceptual and technique based. The procedure section should reference the lab manual and include any changes that were made to the procedure in the lab manual during lab.

The data section for this lab is very large. A fill in the blank worksheet has been provided, but you should create a data table for your lab report. This can be in any format, you can put all the information in one table or split it, just make sure the table covers all the information found in the worksheet.

Work Sheet for Calorimetry

Part A
Exact volume of cold water (to the nearest 0.1 mL) ___________
Temperature of cold water (in cup) ___________
Exact volume of hot water (to the nearest 0.1 mL) ___________
Temperature of hot water (in cylinder) ___________

Part A Calculations:
Mass of cold water (assume density = 1.00 g/mL) ___________
T_f from graph by extrapolation ___________
DT_HW for hot water___________
DT_CW for cold water ___________
q_HW for hot water (use q_HW = m cDT_HW) ___________
q_CW for cold water (use q_CW = m c DTcw)___________
q_Cal for the cup (use |q_HW| = |q_CW |1 q_Cal, solve for q_Cal) ___________
Ccup for the cup (use q_Cal = C_Cup DT) ___________
Which DT should be used?

Part B
Description of sample.
Exact volume of 100 mL HCl (to the nearest 0.1 mL) ___________
Initial temperature of HCl (in cup)___________
Exact mass of Mg (to the nearest 0.001g) ___________

Part B Calculations:
Mass of HCl solution (use the density of water for HCl = 1.00 g/mL) ___________
___________
DT_HCl for HCl ___________
q_HCl for HCl solution (use q_HCl= m c DT_HCl) ___________
q_Cal for the cup (use q_Cal = C_cupDT_HCl) ___________
q_RXN (use q_Rxn = (q_HCl + q_Cal)) ___________
DH_RXN for Mg (use DH_Rxn = q_Rxn/n_Mg) ___________

Write the net reaction which took place in the cup.

Part C
Description of sample.
Exact volume of 100 mL HCl (to the nearest 0.1 mL)___________
Temperature of HCl (in cup) ___________
Exact mass of MgO (to the nearest 0.001g)___________

Part C Calculations:

(highest temperature reached) ___________
DT_HCl for HCl ___________
q_HCl for HCl solution (use q_HCl = m c DT_HCl) ___________
q_cal for the cup (use q_cal = C_Cup DT_HCl) ___________
q_RXN (use q_RXN = (q_HCl + q_cal)) ___________
DH_RXN for MgO (use DH_Rxn = q_Rxn/n_Mg)___________

Write the net reaction that took place in the cup.

Most of the calculations are explained in the worksheet above. Recall though that the change is temperature (DT) is defined as: DT = Final Temperature – Initial Temperature. For each part (A, B and C) include a table of some type with the time and temperature data gathered in lab. For each part a temperature vs. time graph for each run should be included. These graphs are needed to determine T_F. To do this draw a trendline and extrapolate the line to the time the two substances were mixed (probably around 60 seconds), draw a horizontal straight line from that point to the y-axis and record the temperature at which the line and y-axis intercept. Example Graph.

The calculation section should in include temperature vs. time graphs for each part. All graphing guidelines apply here. Sample calculations should be included for the following: the heat capacity of the calorimeter, heat of reaction for both parts B and C, and DH for both parts B and C. Next using your experimental values of DH_Rxn from parts B and C and Hess’s Law calculate the DH_Rxn for

Be sure to show the equations and set up used. Finally compare the literature value of DH_Rxn for the reaction above with the value you calculated and give the percent error in your experiment. Recall the percent error formula:

The conclusion section for this experiment should be several well developed paragraphs. These paragraphs should cover the following information: A discussion on how the various data was arrived upon, this should include but is not limited to 1) the calculation of the maximum temperature of the reaction in Experiment A, 2) the heat of reaction for hot and cold water, 3) the heat of reaction of the calorimeter cup and 4) the heat capacity of the cup.

For Parts B and C: 1) the maximum temperature achieved, 2) the heat of reaction of the solution, cup and reaction and 3) DH_Rxn. Be sure to provide some type of discussion of these values. Also report the overall reaction being studied and the DH_Rxn values found using both experiment and literature values. Be sure to discuss difference in these values as well as the percent error in the experiment. Finally discuss any errors in the experiment.

Answer the following Questions:

1. What is the difference between the heat (q) of a reaction and the reaction enthalpy (DH_RXN) ?

2. Why is T_final taken from extrapolating back to the beginning of the experimental run rather than from the last temperature reading taken?