If the molar enthalpy of combustion of ethane is -1.56 MJ/mol, how much heat is
produced in the burning of;
a) 5.0 mol of ethane b) 45 g of ethane
a) what is 5.0mol*(1.56MJ/mol)?
b) what is 45/molmassethane*1.56MJ/mole?
To calculate the heat produced in the burning of a substance, we need to use the molar enthalpy of combustion and the amount of the substance consumed.
a) 5.0 mol of ethane:
We can directly use the given molar enthalpy of combustion to calculate the heat produced since we have the number of moles of ethane.
The heat produced can be calculated using the formula:
Heat produced = Molar enthalpy of combustion × Number of moles
Given:
Molar enthalpy of combustion of ethane = -1.56 MJ/mol
Number of moles of ethane = 5.0 mol
Calculating:
Heat produced = -1.56 MJ/mol × 5.0 mol
Heat produced = -7.80 MJ (negative sign indicates that heat is released during combustion)
Therefore, 5.0 mol of ethane produces -7.80 MJ of heat during combustion.
b) 45 g of ethane:
To calculate the heat produced when given the mass of the substance, we need to convert the mass of ethane into moles first.
Given:
Mass of ethane = 45 g
Molar mass of ethane = 30.07 g/mol
Calculating moles of ethane:
Number of moles = Mass / Molar mass
Number of moles = 45 g / 30.07 g/mol
Calculating:
Number of moles ≈ 1.495 mol (rounded to three decimal places)
Now we can use the calculated number of moles and the molar enthalpy of combustion to find the heat produced:
Heat produced = Molar enthalpy of combustion × Number of moles
Heat produced = -1.56 MJ/mol × 1.495 mol
Calculating:
Heat produced ≈ -2.33 MJ (rounded to two decimal places)
Therefore, 45 g of ethane produces approximately -2.33 MJ of heat during combustion.