5.3 Exercise 47

Propane, C₃H₈, is a hydrocarbon that is commonly used as a fuel.

(a) Write a balanced equation for the complete combustion of propane gas.

(b) Calculate the volume of air at 25 °C and 1.00 atmosphere that is needed to completely combust 25.0 grams of propane. Assume that air is 21.0 percent O₂ by volume. (Hint: We will see how to do this calculation in a later chapter on gases—for now use the information that 1.00 L of air at 25 °C and 1.00 atm contains 0.275 g of O₂.)

(c) The heat of combustion of propane is −2,219.2 kJ/mol. Calculate the heat of formation, $\Delta H_{\text{f}}^{\circ}$ of propane given that $\Delta H_{\text{f}}^{\circ}$ of H₂O(l) = −285.8 kJ/mol and $\Delta H_{\text{f}}^{\circ}$ of CO₂(g) = −393.5 kJ/mol.

(d) Assuming that all of the heat released in burning 25.0 grams of propane is transferred to 4.00 kilograms of water, calculate the increase in temperature of the water.