amount of heat generated by the combustion of 245 g of CH3OH in 2CH3OH(l)+3O2(g)=2CO2+4H2O(l)
dHrxn = delta H reaction.
dHrxn = (n*dHf products) - (n*dHf reactants)
To determine the amount of heat generated by the combustion of 245 g of CH3OH, you need to use the concept of molar conversions and the enthalpy of combustion of methanol.
First, you need to find the number of moles of CH3OH. To do this, divide the given mass (245 g) by its molar mass. The molar mass of CH3OH can be calculated by adding up the atomic masses of each element in the compound.
Carbon (C) has an atomic mass of approximately 12.01 g/mol.
Hydrogen (H) has an atomic mass of approximately 1.01 g/mol.
Oxygen (O) has an atomic mass of approximately 16.00 g/mol.
So, the molar mass of CH3OH = (12.01 g/mol × 1) + (1.01 g/mol × 4) + (16.00 g/mol + 1) = 32.04 g/mol.
Now, divide the given mass of CH3OH (245 g) by its molar mass (32.04 g/mol) to get the number of moles:
245 g ÷ 32.04 g/mol ≈ 7.64 mol
Next, you want to determine the amount of heat generated per mole of CH3OH combusted. The balanced equation shows that 2 moles of CH3OH are combusted to produce 2 moles of CO2 and 4 moles of H2O.
Given that the enthalpy change of combustion of 1 mole of CH3OH is -726 kJ/mol (this is usually provided in the question or in a reference table), you can calculate the amount of heat released by multiplying it by the number of moles of CH3OH:
-726 kJ/mol × 7.64 mol = -5552.64 kJ
Thus, approximately -5552.64 kJ of heat is generated by the combustion of 245 g of CH3OH. The negative sign indicates that the process is exothermic (releasing heat).