焓变计算器 — 公式

Van der Waals Equation

Formula

[P + a(n/V)²] × [V - nb] = nRT

Solving for P: P = nRT/(V - nb) − a(n/V)²

Where:

  • a = correction for intermolecular attraction (L²·atm/mol²)
  • b = correction for molecular volume (L/mol)
  • Other variables as in the ideal gas law

    • The a term reduces pressure (attraction pulls molecules inward). The b term reduces available volume.

    计算示例

    1 mol of N₂ (a = 1.36, b = 0.0318) at 300 K in 1 L.

    1. P = nRT/(V - nb) - a(n/V)²
    2. P = (1)(0.08206)(300)/(1 - 1×0.0318) - 1.36(1/1)²
    3. P = 24.618/0.9682 - 1.36
    4. P = 25.42 - 1.36
    5. P = 24.06 atm