To find:
a) Calculate the fuel value of
b) How much heat is released during the combustion of
c) How many grams of
Answer to Problem 9.109QA
Solution:
a) Fuel value of
b)
c)
Explanation of Solution
1) Concept:
Fuel value is the amount of energy generated by complete combustion of a particular mass of fuel (hydrocarbon, generally
This can be calculated from the enthalpy change for combustion reaction
The value for heat of combustion is in the units
The amount of energy required to raise the temperature can be calculated using mass, specific heat, and change in temperature,
i.e.,
where,
2) Formula:
3) Given:
i)
ii) Amount of
iii) Amount of water
iv) Initial temperature of water =
v) Final temperature of water =
4) Calculations:
a) Calculating fuel value for
Combustion reaction of
Heat of combustion
The molar mass of
Therefore, the fuel value of
Thus, the fuel value for
b) Calculating heat released during the combustion of
Convert the mass in
Converting mass in grams into moles using molar mass as
Heat released for
Therefore, calculating heat released for
Thus,
c) Calculating the amount of
We need to find here first the heat required to heat water, which can be calculated as
Therefore, energy required to increase the temperature of water from
Here we assume that all the heat, which is required to heat water is coming from the combustion of
Converting moles of
Therefore,
Conclusion:
All the heat lost by a combustion reaction is gained by water, assuming the conservation of energy.
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