Physics
Molecular Physics and Gas Laws
Basic Equations
The molecular-kinetic theory (MKT) explains the structure of matter through the motion of molecules.
- Mendeleev-Clapeyron equation: pV = νRT, where R = 8,31 J/(mol·K).
- Avogadro constant: N_A = 6·10²³ mol⁻¹.
- Temperature in kelvins: T(K) = t(°C) + 273.
- Basic equation of MKT: p = (1/3)·n·m·v² = (2/3)·n·E_k.
- Average kinetic energy of a molecule: E_k = (3/2)·kT, where k = 1,38·10⁻²³ J/K is the Boltzmann constant.
Gas Laws
| Process | Constant | Law |
|---|---|---|
| Isothermal | T | pV = const (Boyle-Mariotte) |
| Isobaric | p | V/T = const (Gay-Lussac) |
| Isochoric | V | p/T = const (Charles) |
- If the pressure increases 3 times in an isothermal process, the volume decreases 3 times.
- In an isochoric process, if T increases 3 times, the pressure increases 3 times.
- 77 °C = 77 + 273 = 350 K.
Problem-Solving Method
In problems on gas laws, first convert the temperature to kelvins, then write the ratio. For example, in an isobaric process V₂ = V₁·T₂/T₁.