Formula: Entropy Change Due To Volume Change Entropy    Amount of substance    Gas constant    Volume

Formula: Entropy Change Due To Volume Change

Entropy change

The entropy change \( \Delta S = S_2 - S_1 \) of an ideal gas from the initial value \(S_1\) to the final value \(S_2\).

Amount of substance

The amount of substance \(n\) indicates the number of particles (atoms, molecules, or ions) in a substance. It is defined as the ratio of the particle count \( N \) to the Avogadro's constant \( N_{\text A} = 6.022\,140\,76 \cdot 10^{23} \, \frac{1}{\mathrm{mol}} \): $$ n ~=~ \frac{N}{N_{\text A}} $$

In one mole of a substance, there are approximately \(6 \cdot 10^{23}\) particles.

Gas constant

Molar gas constant (also called universal gas constant) is a physical constant from thermodynamics and has the following exact value: $$ R ~=~ 8.314 \, 462 \, 618 \, 153 \, 24 \, \frac{\mathrm J}{\mathrm{mol} \, \mathrm{K}} $$

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