Heat theorem, Nernst

This relationship led to an early formulation of the Third Law known as the Nernst heat theorem, which states that for any isothermal process... 

The conclusion that can be reached from the Nernst heat theorem is that the total entropy of the products and the reactants in a chemical reaction must be the same at 0 Kelvin. But nothing in the statement requires that the entropy of the individual substances in the chemical reaction be zero, although a value of zero for all reactants and products is an easy way to achieve the result of equation (4.17). 

Nernst heat theorem 164-5 nickel chloride, heat capacity 180 nitric acid, heat capacity 224-5 nitric oxide, entropy of 173 nitrogen... 

Third Law of Thermodynamics. Also referred to as the Nernst heat theorem, this law states that it is impossible to reduce the temperature of any system, via a finite set of operations, to absolute zero. For any changes involving perfectly crystalline solids at absolute zero, the change in total entropy is zero (thus, A5qk = 0). A corollary to this statement is that every substance, at T > 0 K, must have a positive and finite entropy value. The entropy of that substance is zero only at absolute zero when that substance is in pure, perfect crystalline form. See Entropy... 

The calculation of AG from the caloric data is straightforward, independent of the path, that is, whether the reaction takes place in a single step or through a series of steps by using Hess s law and Nernst heat theorem [15-17]. Furthermore, we can calculate AG for the reaction of interest from the combination of other reactions involved for which the thermodynamic data are known. However, both the initial and final states in many cases are hypothetical. Even in the case of measurements executed very carefully and accurately, there might be problems in defining the states of the compounds, or even metals ( ) that take part in the reaction. 

NERNST HEAT THEOREM. For a homogeneous system, the rate of change of the free energy with temperature, as well as the rate of change of heat content with tempeiature, approaches zero as the temperature approaches absolute zero. 

See also Nernst Effect Nernst Heat Theorem Nernst-Thompson Rule and Thermodynamics. 

The third law (also called the Nernst heat theorem) states that all perfectly ordered crystalline substances have zero entropy at absolute zero temp... 

In 1906 Nernst proposed the principle that, for any change of state in a condensed system, the values of (5 AG/8T)P and (8 AH/8T)P n become zero at absolute zero [16]. This principle became known as the Nernst heat theorem. The consequences of the theorem are that... 

The supposed differences between chemical constants determined from vapour pressures (7/) and from chemical equilibrium data from the Nernst Heat Theorem Jn found by Eucken, Karwat, and Fried, are illusory, and due to inaccuracies in the experiments made in Eucken s laboratory, The supposed constant differences between the calorimetric and optical values (from moments of inertia found from band spectra. or otherwise) listed, with a theoretical explanation, by Eucken, Karwat, and Fried, are also illusory for the same reason. The relation between the spectroscopic and calorimetric entropies, as found from experimental results meriting confidence, is fully discussed in 70.11 and 26-29.IV. Apart from the incorrect data used by Eucken, Karwat, and Fried, 11 their method of extrapolation of specific heats of gases to 0°K. is much cruder than they suspected. 12... 

Equation (14.12) enables us to make a direct test of the Nernst heat theorem, for if this is valid then s 0, 0) is zero and... 

This observation is the Nernst heat theorem, named after its discoverer, the German physicist Walther Nernst. It immediately suggests a choice of reference state The entropy of any pure element in its equilibrium state is defined to approach zero as T approaches 0 K. From the Nernst theorem, the entropy change for any chemical reaction, including one in which elements react to give a pure compound, approaches zero at 0 K. The most general form of this statement is the third law of thermodynamics ... 

Re Entry [109], Ref. [109] Footnote 5 on p. 494 of Ref. [109] concerns "a residual inequivalence" between the Nernst heat theorem and unattainability principle, with the former construed as more fundamental. 

But m the neighbourhood of absolute zero, the Nernst Heat Theorem states that the molecular heats of the condensed (liquid or solid) reactants minus the... 

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