How many kilojoules are released when 85.0g methanol is burned?
I don't have all of the heats of combustion memorized. I can help if you have the data.
To determine the amount of energy released when 85.0g of methanol is burned, we need to use the concept of molar mass and the enthalpy of combustion of methanol.
First, let's find the molar mass of methanol (CH3OH):
- The atomic mass of carbon (C) is 12.01 g/mol.
- The atomic mass of hydrogen (H) is 1.01 g/mol.
- The atomic mass of oxygen (O) is 16.00 g/mol.
Adding up the atomic masses:
(1 * 12.01 g/mol) + (4 * 1.01 g/mol) + (1 * 16.00 g/mol) = 32.04 g/mol.
Now, we can calculate the number of moles of methanol using the given mass:
Number of moles = mass / molar mass
Number of moles = 85.0g / 32.04 g/mol ≈ 2.6528 mol (rounded to four decimal places).
Next, we need to determine the enthalpy of combustion (ΔH) of methanol. The enthalpy of combustion represents the amount of energy released when one mole of a substance combusts under standard conditions. The enthalpy of combustion of methanol is approximately -726 kJ/mol.
Finally, we can calculate the energy released when 85.0g of methanol is burned:
Energy released = moles of methanol * enthalpy of combustion
Energy released = 2.6528 mol * -726 kJ/mol
Energy released ≈ -1925.25 kJ
Therefore, approximately 1925.25 kilojoules (rounded to two decimal places) are released when 85.0g of methanol is burned.