Chemistry Reference
In-Depth Information
Analysis
1. Write the molecular formula for each fuel on Data Table 2. Calculate
the molar (M) mass for each of the three fuels, using the molecular
formulas. Record the M mass on Data Table 2.
2. Subtract the final mass of each spirit burner from its initial mass in
order to calculate the mass of fuel used for each of the three trials
and record them on Data Table 2.
3. Use the mass of each of the three fuels used and each fuel's molar
mass to calculate the mol of fuel used:
moles =
mass
M mass
Record the moles on Data Table 2.
4. Calculate the change in temperature that occurred in each of the
three trials (final temperature − initial temperature) and record it on
Data Table 2.
5. For this laboratory, we will assume that all of the energy from the
combustion of the fuel was absorbed by the water. Therefore, the
amount of energy gained by the water will be equal to the heat of
combustion for the fuel. Calculate the heat of the reaction for each
of the three fuels using the equation
q
=
m C
∆
T
, where
q
= heat energy
m
= mass of water (assume that 1 ml of water weighs 1 g)
C
= specific heat of water (4.184 joules (J)/g
°
C)
∆
T
= change in temperature in
°
C
6. Convert the heat of each reaction from joules to kilojoules (kJ) by
dividing by 1,000.
7. Calculate the amount of heat per mole of each substance by
dividing the heat of reaction by the moles of fuel (from Analysis
question 3). The units for the heat of combustion will be in kJ/mol.
8. Which fuel had the highest heat of combustion? What
characteristics of this fuel do you think caused it to release more
energy than the others?
9. Look up the actual heat of combustion for each of the fuels you
used in this experiment. Calculate your percent error:
actual value −
experimental value−actual value
x 100%
actual value
