Practice

PV = nRT Formula – Ideal Gas Practice

PV = nRT — Ideal gas law (SI: Pa, m³, mol, K)

For an ideal gas, PV = nRT relates pressure, volume, amount of substance, and absolute temperature. Use kelvin, never Celsius, in the formula.

Guide — how to use this formula

1. 1. Convert °C → K: T = t + 273.
2. 2. Match R to units (8.31 for Pa·m³).
3. 3. P = nRT/V; rearrange for V, n, or T.
4. 4. At fixed V and n, P ∝ T.

Derivation

Combining Boyle, Charles, and Avogadro gives the ideal gas law:

1. Ideal gas law:
   PV = nRT
2. Solve for pressure:
   P = \frac{nRT}{V}

With R = 8.31 J/(mol·K), use Pa and m³.

Examples

Example: n = 1, T = 300 K, V = 0.025 m³

P ≈ nRT/V ≈ 99,720 Pa.

Example: °C trap

27 °C → 300 K before substituting.

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