I am attaching the two documents here also!

3-11: Heat of Reaction: MgO(s) + HCl(aq)
Energy is either absorbed or released for all chemical reactions, and we call this energy the enthalpy of
reaction (Hrxn). If the enthalpy of reaction is positive, then we say that the energy was absorbed or that
the reaction was endothermic. If the enthalpy of reaction is negative, then we say that energy was released
or that the reaction was exothermic. Most chemical reactions are exothermic. In this problem, you will
measure the amount of heat released when solid MgO is reacted with aqueous HCl to form water and then
you will calculate the heat of reaction.
MgO(s) + 2 HCl(aq) ↔ H2O(l) + MgCl2(aq)
1. Start Virtual ChemLab, select Thermodynamics, and then select Heat of Reaction: MgO + HCl from
the list of assignments. The lab will open in the Calorimetry laboratory.
2. There will be a bottle of MgO near the balance. A weigh paper will be on the balance with
approximately 2.81 g MgO on the paper. Record the mass of MgO in the data table.
3. The empty calorimeter will be on the lab bench and there will also be a beaker filled with 100.0 mL
of 1.000 M HCl. Drag the beaker to the calorimeter until it snaps into place and pour the HCl into the
calorimeter. Make certain the stirrer is On (you should be able to see the shaft rotating). In the
thermometer window click Save to begin recording data. Allow 20-30 seconds to obtain a baseline
temperature of the HCl solution. Drag the weigh paper containing the MgO sample over to the
calorimeter and drop the sample in. Observe the change in temperature until it reaches a maximum
and then record data for an additional 20-30 seconds. Click Stop in the temperature window. (You
can click on the clock on the wall labeled Accelerate to accelerate the time in the laboratory.) A data
link icon will appear in the lab book. Click the data link icon and record the temperature before
adding the MgO and the highest temperature after adding the MgO in the data table. (Remember that
the water will begin to cool down after reaching the equilibrium temperature.)
Data Table
Mass MgO (g)
initial temperature (C)
final temperature (C)

MgO/HCl
2.8045 g
25.00oC
46.33oC

4. Is the observed reaction endothermic or exothermic? What will be the sign of Hrxn?
The reaction is exothermic. The sign of Hrxn will be negative.

5. Calculate the change in temperature, T. ...