Joule per Kelvin

R is obtained in joules per kelvin per mole R = 8.314 J-K-1-mol" Table 4.2 lists the values of R in a variety of different units which are useful if volume or pressure is reported in other than SI units. For instance, it is sometimes convenient to use R in liter-atmospheres per kelvin per mole R = 8.206 X 10 "2 L-atnvk -mol... 

A note on good practice Note that the entropy change for 1 mol of a substance is reported differently from the entropy change per mole the units of the former are joules per kelvin (J-K ), those of the latter are joules per kelvin per mole (J-K -mol ). 

Propose the argument that, for any liquid at atmospheric pressure (that is, a liquid that boils above room temperature when the external pressure is 1 atm), the numerical value of AHvlp in joules per mole is greater than the numerical value of ASvap in joules per kelvin per mole. (Explain and justify each step and any assumptions.)... 

The SI units for entropy is joules per kelvin. If irrevers-ibihty occurs at any point in the process under consideration, then dS > dqlT. The entropy of an isolated system undergoing an irreversible process always increases (in other words, for any isolated system AS > 0). 

A thermodynamic function, symbolized by /, equal to the negative of the Helmholtz energy divided by the absolute temperature thus, J = -AIT. The SI units are joules per kelvin. See also Planck Function Helmholtz Energy... 

It is important to note that the entropies of gases are larger than those of liquids or solids. This is because entropy is a function of the degree of randomness or disorder at the molecular level. Customarily, S° values are given in joules per kelvin per mole, whereas AG° and AH° are given in kilojoules remember to multiply the latter by 1000 when doing calculations. The entropy of formation of liquid H20 (reaction 2.14) is then... 

Entropy is measured in units of joules per kelvin (or °C) or calories per K, the latter sometimes being abbreviated as e. u. (entropy units). Since the melting of ice at 0°C is a reversible process, the second law asserts that the entropy of the surroundings decreases by the same amount that the entropy of the water increases. The value of T AS is numerically equal to the heat of fusion, 6.008 kj mol1 in the case of water at 0°C. Thus, the entropy increase in the ice as it melts at 0°C is 6.008 x 103 J/273.16 K = 22.0 J K1. 

JOULE PER KELVIN (J/K). A unit of heat capacity urul entropy. 

The specific and molar heat capacities of some common substances are given in Table 6.1. Note that, although the values of the specific heat capacities are listed in joules per degree Celsius per gram (J-(°C) 1 -g 1), they could equally well be reported in joules per kelvin per gram (J-K 1-g ) with the same numerical values, because the size of the Celsius degree and the kelvin are the same. We can calculate the heat capacity of a substance from its mass and its specific heat capacity by rearranging the definition Cs = dm into C = mCs. Then we can use... 

STRATEGY We need to identify the change in the number of moles of gas molecules and then use Eq. 28. For R, use the value in joules per kelvin per mole. 

Note that the entropy of the water increases as a result of the flow of heat into it and that the units of entropy are joules per kelvin (J-K 1). 

The amount of molecular randomness in a system is called the system s entropy (S). Entropy has the units J/K (joules per kelvin, not kilojoules per kelvin) and is a quantity that can be determined for pure substances, as we ll see in Section 17.5. The larger the value of S, the greater the molecular randomness of the particles in the system. Gases, for example, have more randomness and higher entropy than liquids, and liquids have more randomness and higher entropy than solids (Figure 8.13). 

Ssoiute The unit of AH, AS, and AGmix is Joules per Kelvin.11 The 0 temperature is that temperature where AHmix = 0 and polymer dissolution exhibiting ideal behavior is instigated by AS only. 

But a few processes that are endothermic can occur easily. Why Another factor known as entropy can determine if a process will occur. Entropy, S, is a measure of the disorder in a system and is a thermodynamic property. Entropy is not a form of energy and has the units joules per kelvin, J/K. A process is more likely to occur if it is accompanied by an increase in entropy, that is, A5 is positive. 

The table below shows molar heat capacities (joules per kelvins x mole) of elements and compounds. Use it to answer questions 10 through 13. 

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