85. 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 per liter.) (c) The heat of combustion of propane is −2,219.2 kJ/mol. Calculate the heat of formation, ΔH∘fΔHf° of propane given that ΔH∘fΔHf° of H2O(l) = −285.8 kJ/mol and ΔH∘fΔHf° 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.
85. 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 per liter.)
(c) The heat of combustion of propane is −2,219.2 kJ/mol. Calculate the heat of formation, ΔH∘fΔHf° of propane given that ΔH∘fΔHf° of H2O(l) = −285.8 kJ/mol and ΔH∘fΔHf° 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.
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