Dans le même dispositif expérimental que pour l'exercice...

Dans le même dispositif expérimental que pour l'exercice précédent, et à partir de la même situation initiale, on introduit dans le cylindre $0,15 \mathrm{~mol}$ d'argon. Que peut-on dire des variations éventuelles de la pression totale et des pressions partielles du diazote et du dihydrogène : si le piston est bloqué, $>$ si le piston est libre,

Dans le même dispositif expérimental que pour l'exercice précédent, et à partir de la même situation initiale, on introduit dans le cylindre $0,15 \mathrm{~mol}$ d'argon.
Que peut-on dire des variations éventuelles de la pression totale et des pressions partielles du diazote et du dihydrogène :
si le piston est bloqué,
$>$ si le piston est libre,

Key Concepts

Inert Gas Addition and Its Effect on Gas Mixtures

Adding an inert gas, which does not react chemically with the other components, increases the total number of moles in the system without directly altering the mole numbers of the reactive gases. This concept demonstrates that while the total pressure increases in a confined volume (due to the added gas), the partial pressures of the original gases depend solely on their own mole counts and not on the inert gas added.

Ideal Gas Law

This principle (PV = nRT) relates pressure, volume, temperature, and the number of moles of a gas. It is essential for understanding how changes in the quantity of gas (n) or alterations in volume (V) directly affect the pressure (P) when temperature (T) is constant. In the problem, it explains why adding an inert gas to a fixed-volume container increases the total pressure, while if the volume can adjust, the pressure may remain constant.

Dalton's Law of Partial Pressures

Dalton's law states that in a mixture of non-reacting gases, the total pressure is equal to the sum of the pressures that each gas would exert if it were alone in the container. This law is crucial for analyzing how the partial pressures of nitrogen and hydrogen remain unaffected by the addition of an inert gas, since only the number of moles contributing to each individual gas’s pressure remains constant.

Isochoric and Isobaric Processes

These terms describe processes occurring at constant volume (isochoric) and constant pressure (isobaric). In a fixed-volume (blocked piston) scenario, any addition of gas increases the total pressure, because the volume does not change. In contrast, when the piston is free and the system can expand (approximating an isobaric process), the pressure remains nearly constant despite the addition of extra moles of gas, meaning the reactive gases’ partial pressures remain unchanged.

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