Consider the combustion of propane:

C3H8 + 5CO2 -> 3CO2 + 2H20. Delta H = -2221 kJ.

What mass of propane must be burned to furnish this amount of energy assuming the heat transfer process is 60.% efficient?

To find the mass of propane that must be burned to produce a specific amount of energy, we need to first calculate the heat transfer involved.

Given that the enthalpy change for the combustion of propane (∆H) is -2221 kJ, we can use this information to find the amount of energy (Q) transferred by the combustion process.

Q = ∆H

Q = -2221 kJ

Next, we need to account for the efficiency of the heat transfer process. The efficiency is given as 60%, which means that only 60% of the energy produced is actually transferred.

Efficiency = 60% = 0.60

To calculate the actual amount of energy transferred (Q_actual), we multiply the efficiency by the total energy produced (Q) as follows:

Q_actual = Efficiency * Q

Q_actual = 0.60 * -2221 kJ

Now, we have the amount of energy transferred (Q_actual). To determine the mass of propane burned, we can use the molar ratio between propane and energy.

The balanced equation for the combustion of propane shows that for every mole of propane burned, -2221 kJ of energy is released. So we need to calculate the moles of propane burned, and then convert that to its mass.

To do this, we will use the molar mass of propane, which is 44.1 g/mol.

Step 1: Convert the energy transferred (Q_actual) from kilojoules to joules.

Q_actual = 0.60 * -2221 kJ = -1332.6 kJ

Q_actual = -1332.6 kJ = -1332.6 * 1000 J

Step 2: Calculate the number of moles of propane burned.

Number of moles = Q_actual / ∆H

Number of moles = (-1332.6 * 1000 J) / (-2221 kJ)

Step 3: Convert moles to grams using the molar mass of propane.

Mass of propane = Number of moles * molar mass

Mass of propane = Number of moles * 44.1 g/mol

By following these calculations, you can determine the mass of propane that must be burned to furnish the given amount of energy with 60% efficiency.