Answers for the Heat of Combustion of Cellulose and its Derivatives
The balanced reactions are:
Glucose (to represent cellulose):
Glucose acetate (to represent cellulose acetate):
Glucose nitrate (to represent cellulose nitrate):
Notice that the reaction for glucose nitrate can be balanced without adding oxygen. (What does that mean in terms of the fire triangle?) Assuming that ammonia is the product, the reaction can be balanced without producing any water.
The calculated heats of reaction (heats of combustion):
Glucose:
heat of reaction = [6 x heat of formation of CO2 (g) + 6 x heat of formation of H2O (g)] -
[heat of formation of glucose]
Heat of reaction = [6 x (-393.5 kJ/mole) + 6 x (-241.8 kJ/mole)] - [-1250 kJ/mole]
heat of reaction = -2560 kJ/mole
Glucose acetate:
heat of reaction = [12 x heat of formation of CO2 (g) + 9 x heat of formation of H2O (g)] -
[heat of formation of glucose acetate]
Heat of reaction = [12 x (-393.5 kJ/mole) + 9 x (-241.8 kJ/mole)] - [-1950 kJ/mole]
heat of reaction = -4950 kJ/mole
Glucose nitrate:
heat of reaction = [6 x heat of formation of CO2(g) + 3 x heat of formation of NH3(g)] -
[heat of formation of glucose nitrate]
Heat of reaction = [6 x (-393.5 kJ/mole) + 3 x (-46.1 kJ/mole)] - [-860 kJ/mole]
heat of reaction = -1640 kJ/mole
For cellulose:
From the chemical structure of glucose one mole is 180 grams (the molar mass or molecular weight is 180 g/mole). From the calculation we know that when one mole, or 180 grams, of glucose burns it releases 2560 kJ of energy (the heat of reaction is -2560 kJ/mole). So on a per gram basis, the heat released is 2560 kJ divided by 180 g or -14.2 kJ/gram.
For cellulose acetate:
From the chemical structure of glucose acetate one mole is 306 grams (the molar mass or molecular weight is 306 g/mole). From the calculation we know that when one mole, or 180 grams, of glucose burns it releases 4950 kJ of energy (the heat of reaction is -4950 kJ/mole). So on a per gram basis, the heat released is 4950 kJ divided by 306 g or -16.2 kJ/gram.
For cellulose nitrate:
From the chemical structure of glucose nitrate one mole is 315 grams (the molar mass or molecular weight is 315 g/mole). From the calculation we know that when one mole, or 315 grams, of glucose burns it releases 1640 kJ of energy (the heat of reaction is -1640 kJ/mole). So on a per gram basis, the heat released is 1640 kJ divided by 315 g or -5.2 kJ/gram.
The answers in tabular form are here.
