Report Contents and Questions
The purpose should be several well constructed sentences that describe the goals of the experiment and the criteria for determining the success or failure of the experiment. The procedure section should reference the lab manual and include any changes that were made to the procedure during lab.
The data section for this lab is very large. A fill in the blank worksheet has been provided, but you should create your own data table for your lab report. This can be in any format. You can put all the information in one table or split it by experimental section, just make sure the table includes all of the information found in the worksheet.
Work Sheet for Calorimetry
Part A Trial 1 Trial 2
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) __________ ___________
Tf from graph by extrapolation __________ ___________
DTHW for hot water __________ ___________
DTCW for cold water __________ ___________
qHW for hot water (use qHW = m cDTHW) __________ ___________
qCW for cold water (use qCW = m c DTcw) __________ ___________
qCal for the cup (use |qHW| = |qCW |+ qCal, solve for qCal) __________ ___________
Ccup for the cup (use qCal = CCup DT) ___________ ___________
Which DT should be used?
Part B
Description of sample.
Exact volume of 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:
Tf from graph by extrapolation ___________
Mass of HCl solution (use the density of water for HCl = 1.00 g/mL) ___________
DTCW for HCl ___________
qHCl for HCl solution (use qCW = m c DDTHCl) ___________
qCal for the cup (use qCal = CcupDTHCl) ___________
qRXN (use qRxn = (qHCl + qCal)) ___________
DHRXN for Mg (use DHRxn = qRxn/nMg) ___________
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:
Tf from graph by extrapolation ___________
DTCW for HCl ___________
qHCl for HCl solution (use qCW = m c DTHCl) ___________
qcal for the cup (use qcal = CCup DTHCl) ___________
qRXN (use qRXN = (qHCl + qcal)) ___________
DHRXN for MgO (use DHRxn = qRxn/nMgo) ___________
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 in 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. A temperature vs. time graph for each run should be included. To determine Tf, draw a trend line and extrapolate the line to the time the two substances were mixed (probably around 60-90 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.
Using your experimental values of DHRxn from parts B and C and Hess’s Law, calculate the DHRxn for
Be sure to show the equations and setup used. Finally, compare your value with the literature value of DHRxn and determine the percent error in your experiment.
The conclusion section for this experiment should be several well developed paragraphs. These paragraphs should cover the following information:
1. What is the difference between the heat (q) of a reaction and the reaction enthalpy (DHRXN) ?
2. Why is Tfinal taken from extrapolating back to the beginning of the experimental run rather than from the last temperature reading taken?
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