Back
Problem 105b
Palmitic acid (C16H32O2) is a dietary fat found in beef and butter. The caloric content of palmitic acid is typical of fats in general. Which dietary substance (sugar or fat) contains more Calories per gram? The standard enthalpy of formation of palmitic acid is -208 kJ/mol and that of sucrose is -2226.1 kJ/mol. [Use H2O(l) in the balanced chemical equations because the metabolism of these compounds produces liquid water.]
- Hydrogen and methanol have both been proposed as alternatives to hydrocarbon fuels. Use standard enthalpies of formation to calculate the amount of heat released per kilogram of methanol fuel and per kilogram of hydrogen fuel.
Problem 106
Problem 106b
Hydrogen and methanol have both been proposed as alternatives to hydrocarbon fuels. Which fuel contains the most energy in the least mass?
Problem 106c
Hydrogen and methanol have both been proposed as alternatives to hydrocarbon fuels. How does the energy of these fuels compare to that of octane (C8H18)?
- Derive a relationship between ΔH and ΔE for a process in which the temperature of a fixed amount of an ideal gas changes.
Problem 107
Problem 108
Under certain nonstandard conditions, oxidation by O2(g) of 1 mol of SO2(g) to SO3(g) absorbs 89.5 kJ. The enthalpy of formation of SO3(g) is –204.2 kJ under these conditions. Find the enthalpy of formation of SO2(g).
- One tablespoon of peanut butter has a mass of 16 g. It is combusted in a calorimeter whose heat capacity is 120.0 kJ/°C. The temperature of the calorimeter rises from 22.2 °C to 25.4 °C. Find the food caloric content of peanut butter.
Problem 109
Problem 110
A mixture of 2.0 mol of H2(g) and 1.0 mol of O2(g) is placed in a sealed evacuated container made of a perfect insulating material at 25 °C. The mixture is ignited with a spark and reacts to form liquid water. Determine the temperature of the water.
Problem 111d
A 20.0-L volume of an ideal gas in a cylinder with a piston is at a pressure of 3.0 atm. Enough weight is suddenly removed from the piston to lower the external pressure to 1.5 atm. The gas then expands at constant temperature until its pressure is 1.5 atm. Find w.
Problem 112
When 10.00 g of phosphorus is burned in O2(g) to form P4O10(s), enough heat is generated to raise the temperature of 2950 g of water from 18.0 °C to 38.0 °C. Calculate the enthalpy of formation of P4O10(s) under these conditions.
Problem 113
The ΔH for the oxidation of sulfur in the gas phase to SO3 is –204 kJ/mol and for the oxidation of SO2 to SO3 is 89.5 kJ/mol. Find the enthalpy of formation of SO2 under these conditions.
Problem 114
The ΔH°f of TiI3(s) is –328 kJ/mol and the ΔH ° for the reaction 2 Ti(s) + 3 I2(g) → 2 TiI3(s) is –839 kJ. Calculate the ΔH of sublimation of I2(s), which is a solid at 25 °C.
Problem 115
A gaseous fuel mixture contains 25.3% methane (CH4), 38.2% ethane (C2H6), and the rest propane (C3H8) by volume. When the fuel mixture contained in a 1.55 L tank, stored at 755 mmHg and 298 K, undergoes complete combustion, how much heat is emitted? (Assume that the water produced by the combustion is in the gaseous state.)
Problem 116
A gaseous fuel mixture stored at 745 mmHg and 298 K contains only methane (CH4) and propane (C3H8). When 11.7 L of this fuel mixture is burned, it produces 769 kJ of heat. What is the mole fraction of methane in the mixture? (Assume that the water produced by the combustion is in the gaseous state.)
- A copper cube with an edge measuring 1.55 cm and an aluminum cube with an edge measuring 1.62 cm are both heated to 55.0 °C and submerged in 100.0 mL of water at 22.2 °C. What is the final temperature of the water when equilibrium is reached? (Assume a density of 0.998 g/mL for water.)
Problem 117
- A pure gold ring and a pure silver ring have a total mass of 14.9 g. The two rings are heated to 62.0 °C and dropped into 15.0 mL of water at 23.5 °C. When equilibrium is reached, the temperature of the water is 25.0 °C. What is the mass of each ring? (Assume a density of 0.998 g/mL for water.)
Problem 118