The maximum amount of energy produced by a reaction that can be theoretically harnesses as work is equal to

When a rocket is launched, the burning gases are the source of the motion. If the system is the rocket (including fuel), what is the sign of the work?

9.12 PV-work occurs when volume changes and pressure remains constant. If volume is held constant, can PV-work be done? What happens to Equation 9.2 when volume is held constant? E=q+w (9.2)

Explain why absolute enthalpies and energies cannot be measured, and only changes can be determined.

Coal is used as a fuel in some electric-generating plants. Coal is a complex material, but for simplicity we may consider it to be a form of carbon. The energy that can be derived from a fuel is sometimes compared with the enthalpy of the combustion reaction: C(s)+O2(g)CO2(g) Calculate the standard enthalpy change for this reaction at 25C. Actually, only a fraction of the heat from this reaction is available to produce electric energy. In electric generating plants, this reaction is used to generate heat for a steam engine, which turns the generator. Basically the steam engine is a type of heat engine in which steam enters the engine at high temperature (Th), work is done, and the steam then exits at a lower temperature (Tl). The maximum fraction, f, of heat available to produce useful energy depends on the difference between these temperatures (expressed in kelvins), f = (Th Tl)/Th. What is the maximum heat energy available for useful work from the combustion of 1.00 mol of C(s) to CO2(g)? (Assume the value of H calculated at 25C for the heat obtained in the generator.) It is possible to consider more efficient ways to obtain useful energy from a fuel. For example, methane can be burned in a fuel cell to generate electricity directly. The maximum useful energy obtained in these cases is the maximum work, which equals the free-energy change. Calculate the standard free-energy change for the combustion of 1.00 mol of C(s) to CO2(g). Compare this value with the maximum obtained with the heat engine described here.

9.42 Why is enthalpy generally more useful than internal energy in the thermodynamics of real world systems?

A small car is traveling at twice the speed of a larger car, which has twice the mass of the smaller car. Which car has the greater kinetic energy? (Or do they both have the same kinetic energy?)

A 220-L cylinder contains an ideal gas at a pressure of 150 atm. If the gas is allowed to expand against a constant opposing pressure of 1.0 atm, how much work is done? The expansion will stop when the internal pressure equals the external pressure. Use Boyles law to determine the final volume.

In the process of isolating iron from its ores, carbon monoxide reacts with iron(III) oxide, as described by the following equation: Fe2O3(s)+3CO(g)2Fe(s)+3CO2(g)H=24.8kJ The enthalpy change for the combustion of carbon monoxide is 2CO(g)+O2(g)2CO2(g)H=566kJ Use this information to calculate the enthalpy change for the equation 4Fe(s)+3O2(g)2Fe2O3(s)H=?

Consider the following reaction in the vessel described in Question 57. A(g)+B(g)C(s)For this reaction, E=286 J, the piston moves up and the system absorbs 388 J of heat from its surroundings. (a) Is work done by the system? (b) How much work?