During the combustion of 5.00 g of octane, C8H18, 239.5 kcal (1002 kJ) is released. How many moles of octane must be burned to release 451.4 kcal ?
See the other problem I worked for you. This is similar.
To find out how many moles of octane must be burned to release 451.4 kcal, we need to use the molar mass of octane and the energy released per gram of octane burned.
1. First, calculate the moles of octane for the given energy release of 239.5 kcal:
The energy released per gram of octane burned is 239.5 kcal / 5.00 g = 47.9 kcal/g.
2. Convert the energy release from kcal to kJ:
The energy release is 451.4 kcal * 4.184 kJ/kcal = 1887.74 kJ.
3. Calculate the moles of octane for the new energy release of 1887.74 kJ:
The energy released per gram of octane burned is 1887.74 kJ / 47.9 kcal/g = 39.34 kJ/g.
3. Now, we need to convert the energy release per gram to moles by using the molar mass of octane.
The molar mass of octane (C8H18) can be calculated by summing up the individual atomic masses of carbon (C) and hydrogen (H) in one molecule of octane. The atomic masses are:
- Carbon (C): 12.01 g/mol.
- Hydrogen (H): 1.008 g/mol.
The molar mass of octane is (8 * 12.01 g/mol) + (18 * 1.008 g/mol) = 114.23 g/mol.
4. Now, calculate the number of moles by dividing the energy release per gram by the molar mass of octane:
Number of moles = Energy release per gram / Molar mass of octane
= 39.34 kJ/g / 114.23 g/mol.
Calculating this division will give you the number of moles of octane that must be burned to release 451.4 kcal.