how much heat will be released if 30 grams of octane is burned in excess oxygen?
Do you know the heat of combustion?
To determine the amount of heat released when 30 grams of octane (C8H18) is burned in excess oxygen (O2), we need to calculate the heat of combustion per mole of octane and convert it to grams.
The balanced equation for the combustion of octane is as follows:
2 C8H18 + 25 O2 -> 16 CO2 + 18 H2O
The heat of combustion of octane is -5470 kJ/mol. This means that for every mole of octane burned, 5470 kJ of heat is released.
To calculate the amount of heat released when 30 grams of octane is burned, we need to determine the number of moles of octane in 30 grams.
First, we calculate the molar mass of octane (C8H18):
(8 x Atomic mass of Carbon) + (18 x Atomic mass of Hydrogen)
= (8 x 12.01 g/mol) + (18 x 1.01 g/mol)
= 96.08 g/mol + 18.18 g/mol
= 114.26 g/mol
Next, we use the molar mass to calculate the number of moles of octane:
Number of moles = Mass / Molar mass
Number of moles = 30 g / 114.26 g/mol
Number of moles = 0.2626 mol
Now, we can calculate the heat released when 30 grams of octane is burned:
Heat released = Number of moles of octane x Heat of combustion per mole
Heat released = 0.2626 mol x -5470 kJ/mol
Heat released ≈ -1435 kJ
Therefore, approximately 1435 kJ of heat will be released when 30 grams of octane is burned in excess oxygen.
To determine the amount of heat released when 30 grams of octane (C8H18) is burned in excess oxygen (O2), we need to calculate the heat of combustion.
The balanced equation for the combustion of octane is:
C8H18 + 12.5 O2 -> 8 CO2 + 9 H2O
From the balanced equation, we can deduce that 1 mole of octane produces 8 moles of carbon dioxide (CO2) and 9 moles of water (H2O). We first need to calculate the moles of octane in 30 grams:
Molar mass of octane (C8H18) = (12.011 * 8) + (1.008 * 18) = 114.222 grams/mol
Moles of octane = Mass of octane / Molar mass of octane
= 30g / 114.222 g/mol
≈ 0.262 moles
According to the balanced equation, 1 mole of octane produces 8 moles of carbon dioxide. So, the moles of carbon dioxide produced can be calculated by multiplying the moles of octane by the mole ratio:
Moles of CO2 = Moles of octane * (8 moles CO2 / 1 mole octane)
= 0.262 * 8
≈ 2.096 moles
Next, we can calculate the amount of heat released using the standard enthalpy of combustion (∆H°c) of octane. The standard enthalpy of combustion is the heat released when 1 mole of octane is burned completely.
The standard enthalpy of combustion of octane is approximately -5471 kJ/mol.
Heat released = Moles of CO2 * ∆H°c
= 2.096 moles * -5471 kJ/mol
≈ -11443 kJ (rounded to the nearest whole number)
Therefore, approximately 11443 kJ of heat will be released when 30 grams of octane is burned in excess oxygen.