## How · 1.0 M HCl(aq) · Mg Ribbon

How is Heat of Combustion Measured
Indirectly?

Goals: Commissioned to design an
experiment that will allow us to indirectly measure heat changes within a
reaction, our group will be using Hess’ Law to determine the total enthalpy.

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For investigation 30, we will accomplish this by finding the heat of combustion
for magnesium. The reason we must use indirect methods of measuring and
calculating heat changes is it is risky to merely burn magnesium without proper
lab equipment. Given that we will be creating our own calorimeters, indirect
ways of establishing total enthalpy is the next best option.

Equipment
and Reagent:

·
1.0 M HCl(aq)

·
Mg Ribbon

·
MgO(s)

·
Styrofoam cups

·
Thick cardboard paper

·
Scissors/Box knife

·
Stirrer

·
Thermometer/Temperature Probe

·

·
Scale

Procedures:

1.
Design a calorimeter by stacking two Styrofoam cups
within each other and inserting an insulated cover such as cardboard over the
calorimeter (This prevents loss of heat and allows for more accurate
measurements). Use a sharp instrument such as a scissor or boxknife to poke two
small holes in the cover. These are for the thermometer and stirrer.

2.
Weigh 0.5 to 1.0g of MgO(s) and record its mass.

(INITIAL WEIGHT)

3.
Calculate the amount of HCl(aq) necessary to fully
react with the measured amount of MgO(S) by using the equation MgO(g)
+ 2 H+1(aq) ? Mg+2(aq) + H2O(l)
.

4.
its mass, and reset the scale.

5.
Add the HCl(aq) we calculated in
step 3.

6.
Record the mass of HCl(aq) by subtracting the weight
of the graduated cylinder found in step 4 from the total mass of the HCl(aq)

7.
Add the HCl(aq) to the calorimeter.

8.
Record the initial temperature of the HCl. (INITIAL
TEMPERATURE)

9.
Add the MgO(s) measured in step 2 to the coffee cup
calorimeter and stir till dissolution occurs.

10.  When all
the MgO(s) is added, begin recording temperature fluctuations at a specific
interval such as every 5 or 10 seconds. When the temperature begins to steady,
stop recording.

11.  Find the
highest temperature value and consider this the final temperature that will be
used for Hess’ Law calculations. (FINAL TEMPERATURE)

12.  Calculate
the mass of the solution by adding the initial weights of MgO(s) and HCl.

13.  Calculate
the change in temperature by subtracting the initial temperature from the final
temperature.

14.  Solve for
q=mC?T, given that the specific heat of the solution is
4.184J/ goC. The equation q=?H can be used, since we kept pressure
and volume constant throughout the procedure.

15.  Cut
a piece of Magnesium ribbon about 1-1.5 inches long and record its mass.

(INITIAL WEIGHT)

16.  Calculate
the amount of HCl(aq) needed to fully react with the Mg ribbon, using the
equation Mg(g) + 2 H+1(aq) ?
Mg+2(aq) + H2(g)

17.  Weigh
a graduated cylinder, record its mass, and reset out the scale.

the HCl(aq) we calculated in step 16.

19.  Record
the mass of HCl(aq) by subtracting the weight of the graduated cylinder found
in step 18 from the total mass of the HCl(aq) and graduated cylinder. (INITIAL
WEIGHT)

HCl(aq) to the calorimeter.

21.  Record
the initial temperature of the HCl. (INITIAL TEMPERATURE)

22.  Drop the
measured magnesium strip into the solution and stir till dissolution occurs.

23.  When all
the MgO(s) is added, begin recording temperature fluctuations at a specific
interval such as every 5 or 10 seconds. When the temperature begins to steady,
stop recording.

24.  Find the
highest temperature value and consider this the final temperature that will be
used for Hess’ Law calculations. (FINAL TEMPERATURE)

25.  Use steps
12-14 for the magnesium ribbon portion of the experiment

26.  Repeat
steps #1-26 for the MgO(s) and Mg ribbon, performing two trials for each

Variables
to Control:

·
Pressure

·
Volume

o   Pressure
and volume need to stay constant, so we can use the equation q=?H

·
Amount of MgO(s) used for each trial should be comparable
to find a reasonable value for the average heat conducted.

·
Amount of Mg ribbon used for each trial should comparable
to find a reasonable value for the average heat conducted.

·
Stirring for each trial should be similar. Agitating
one trial more than the other may lead to inconclusive results.

·
Safety
Considerations:

·      Wear a
lab coat, gloves, goggles, and close toed shoes.

·      Keep long
hair tied back.

·      Remove
objects near investigation to prevent spills.

·      Clean
work area after experiment to avoid contamination.

How is Heat of Combustion Measured
Indirectly?

Goals: Commissioned to design an
experiment that will allow us to indirectly measure heat changes within a
reaction, our group will be using Hess’ Law to determine the total enthalpy.

We Will Write a Custom Essay Specifically
For You For Only \$13.90/page!

order now

For investigation 30, we will accomplish this by finding the heat of combustion
for magnesium. The reason we must use indirect methods of measuring and
calculating heat changes is it is risky to merely burn magnesium without proper
lab equipment. Given that we will be creating our own calorimeters, indirect
ways of establishing total enthalpy is the next best option.

Equipment
and Reagent:

·
1.0 M HCl(aq)

·
Mg Ribbon

·
MgO(s)

·
Styrofoam cups

·
Thick cardboard paper

·
Scissors/Box knife

·
Stirrer

·
Thermometer/Temperature Probe

·

·
Scale

Procedures:

1.
Design a calorimeter by stacking two Styrofoam cups
within each other and inserting an insulated cover such as cardboard over the
calorimeter (This prevents loss of heat and allows for more accurate
measurements). Use a sharp instrument such as a scissor or boxknife to poke two
small holes in the cover. These are for the thermometer and stirrer.

2.
Weigh 0.5 to 1.0g of MgO(s) and record its mass.

(INITIAL WEIGHT)

3.
Calculate the amount of HCl(aq) necessary to fully
react with the measured amount of MgO(S) by using the equation MgO(g)
+ 2 H+1(aq) ? Mg+2(aq) + H2O(l)
.

4.
its mass, and reset the scale.

5.
Add the HCl(aq) we calculated in
step 3.

6.
Record the mass of HCl(aq) by subtracting the weight
of the graduated cylinder found in step 4 from the total mass of the HCl(aq)

7.
Add the HCl(aq) to the calorimeter.

8.
Record the initial temperature of the HCl. (INITIAL
TEMPERATURE)

9.
Add the MgO(s) measured in step 2 to the coffee cup
calorimeter and stir till dissolution occurs.

10.  When all
the MgO(s) is added, begin recording temperature fluctuations at a specific
interval such as every 5 or 10 seconds. When the temperature begins to steady,
stop recording.

11.  Find the
highest temperature value and consider this the final temperature that will be
used for Hess’ Law calculations. (FINAL TEMPERATURE)

12.  Calculate
the mass of the solution by adding the initial weights of MgO(s) and HCl.

13.  Calculate
the change in temperature by subtracting the initial temperature from the final
temperature.

14.  Solve for
q=mC?T, given that the specific heat of the solution is
4.184J/ goC. The equation q=?H can be used, since we kept pressure
and volume constant throughout the procedure.

15.  Cut
a piece of Magnesium ribbon about 1-1.5 inches long and record its mass.

(INITIAL WEIGHT)

16.  Calculate
the amount of HCl(aq) needed to fully react with the Mg ribbon, using the
equation Mg(g) + 2 H+1(aq) ?
Mg+2(aq) + H2(g)

17.  Weigh
a graduated cylinder, record its mass, and reset out the scale.

the HCl(aq) we calculated in step 16.

19.  Record
the mass of HCl(aq) by subtracting the weight of the graduated cylinder found
in step 18 from the total mass of the HCl(aq) and graduated cylinder. (INITIAL
WEIGHT)

HCl(aq) to the calorimeter.

21.  Record
the initial temperature of the HCl. (INITIAL TEMPERATURE)

22.  Drop the
measured magnesium strip into the solution and stir till dissolution occurs.

23.  When all
the MgO(s) is added, begin recording temperature fluctuations at a specific
interval such as every 5 or 10 seconds. When the temperature begins to steady,
stop recording.

24.  Find the
highest temperature value and consider this the final temperature that will be
used for Hess’ Law calculations. (FINAL TEMPERATURE)

25.  Use steps
12-14 for the magnesium ribbon portion of the experiment

26.  Repeat
steps #1-26 for the MgO(s) and Mg ribbon, performing two trials for each

Variables
to Control:

·
Pressure

·
Volume

o   Pressure
and volume need to stay constant, so we can use the equation q=?H

·
Amount of MgO(s) used for each trial should be comparable
to find a reasonable value for the average heat conducted.

·
Amount of Mg ribbon used for each trial should comparable
to find a reasonable value for the average heat conducted.

·
Stirring for each trial should be similar. Agitating
one trial more than the other may lead to inconclusive results.

·
Safety
Considerations:

·      Wear a
lab coat, gloves, goggles, and close toed shoes.

·      Keep long
hair tied back.

·      Remove
objects near investigation to prevent spills.

·      Clean
work area after experiment to avoid contamination.

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