Change in internal energy

It is not particularly difficult to find macroscopic measures of interactions between small molecules of the same type, that is, quantities which are proportional to Wii and W22 in Eq. (8.40). Among the possibilities, we consider the change in internal energy AU for the vaporization process for component i. This can be related to Wjj in terms of the lattice model by the expression... 

The integrated terms are simply the specific heat of the unit mass of adsorbent and its associated adsorbate. The specific heat at constant volume has been used for the adsorbate since, theoretically, there is no expansion of the adsorbate volume and the heat required to raise the temperature is the change in internal energy. In practice there will be some expansion and a pessimistically high estimate could use the specific heat at constant pressure The specific heat of the adsorbed phase is in any case difficult to estimate and it is common to approximate it to that of saturated liquid adsorbate at the same temperature. 

AE, AH = changes in internal energy and entlialpy during tlie process... 

The internal energy, E, of any system can change only if energy flows in or out of the system in the form of heat or work. For any process that converts one state (state 1) into another (state 2), the change in internal energy, AE, is given as... 

The change in internal energy on mixing can also be obtained from... 

EXAMPLE 6.5 Calculating the work, heat, and change in internal energy for the expansion of an ideal gas... 

FIGURE 6.16 (a) On the reversible path, the work done in Example 6.5 is relatively large (w = -2.12 kj) because the change in internal energy is zero, heal flows in to maintain constant temperature and constant internal energy. Therefore, q =... 

Consider a process at constant pressure for which the change in internal energy is AU and the change in volume is A V. It then follows from the definition of enthalpy in Eq. 9 that the change in enthalpy is... 

Because heat transferred at constant volume can be identified with the change in internal energy, AU, we can combine Eq. 8 with C = q/AT and define the heat capacity at constant volume, Cv, as... 

Self-Tfst 6.8A Calculate the final temperature and the change in internal energy when 500. J of energy is transferred as heat to 0.900 mol Ne(g) at 298 K and... 

Sei f-Test 6.8B Calculate the final temperature and the change in internal energy... 

Calculate the change in internal energy due to hear and work (Self-Test 6.5). 

Calculate the change in internal energy when an ideal gas is heated (Example 6.6). 

A gas in a cylinder was placed in a heater and gained 5500 kj of heat. If the cylinder increased in volume from 345 mL to 1846 mL against an atmospheric pressure of 750. Torr during this process, what is the change in internal energy of the gas in the cylinder ... 

We then use Eq. 9 of Chapter 6 H = U + PV) to express the infinitesimal change in enthalpy at constant pressure in terms of the change in internal energy dH = dU + Pd V at constant pressure Then we substitute this expression into the first ... 

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