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Title: CHEM 1407 Prelab
Description: Enthalpy of formation of magnesium oxide Pre Lab
Description: Enthalpy of formation of magnesium oxide Pre Lab
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Brianna Marsh
Enthalpy of formation of magnesium oxide Pre Lab
11/14/17
Purpose: Students will determine the heat of formation of magnesium oxide by measuring the
heat of reaction for several reactions and using the principles outlined in Hess’ law
Questions:
a
...
b
...
6 kJ/mol
Mg (s) + 2HCl (aq) → Mg2+(aq) + 2Cl-(aq) + H2 (g)
Δ H1=?
R2
H2O (l) + 2HCl (aq) → Mg2+ (aq) + 2Cl- (aq) +MgO (s)
Δ H2=?
R3
H2O (l) + ½O2 (g) → H2(g)
Δ H3= -285
...
R1
Procedures:
A
...
Obtain a LabQuest with a temperature probe
...
The labQuest should automatically detect the probe and display a
reading similar to below
...
2
...
We will want to record in Celsius during this experiment
...
3
...
Change the “Mode” to “Time Based”
...
Change the “Rate” to “1” samples/s
...
c
...
d
...
4
...
This will bring you to the recording screen
...
B
...
Setup the calorimeter and place the thermometer LabQuest attachment in either CH 1, 2, or 3
slot of the LabQuest
...
2
...
3
...
4
...
Record exact mass of HCl
...
Place the temperature probe into the HCl solution and allow the temperature to
stabilize
...
Warning: any group
who turns on the heat function of the stir/hot plate and causes damage to the calorimeter
will receive a 0 for the experiment
...
5
...
Clean the ribbon using
a scotch pad or sand paper and coil it up so that it will easily fit in the calorimeter (do not place
in the calorimeter yet)
...
6
...
Be sure
the stir bar is spinning (you should be able to hear it, and gently agitate the calorimeter during
the reaction
...
Once the LabQuest recording stops (after 3 min), determine the maximum temperature
recorded
...
The initial and final temperatures can be found at the approximate points along the
curve indicated in Figure 3
...
Dispose of your waste in a labeled beaker and repeat the Steps 2-6 twice more for a total of
three trials
...
9
...
25 g MgO powder instead of Mg ribbon
...
You should have 3 trials for Mg and 3 trials for MgO powder
...
Using your data, make all of the appropriate calculations to determine ΔH1, ΔH2, and
ΔHoverall
...
Use the literature value for Δ Hf ° of MgO to
calculate the percent error
Title: CHEM 1407 Prelab
Description: Enthalpy of formation of magnesium oxide Pre Lab
Description: Enthalpy of formation of magnesium oxide Pre Lab