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Ideal Gas Law

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The ideal gas law, PV = nRT, links a gas's pressure, volume, amount (moles), and temperature through the constant R. Rearrange it to solve for whichever variable is unknown. Two habits keep it honest: temperature goes in Kelvin, and you track which quantities are directly versus inversely related.

UNIT 3 TOPIC 3.4 • IDEAL GAS LAW PV = nRT PLAYGROUND The ideal gas law relating pressure, volume, amount, and temperature. VARIABLES P Pressure (atm) V Volume (L) T Temperature (K) n Moles (mol) R Gas constant P V = n R T the ideal gas law at STP: nRT / P = 22.4 L STP READOUT P 1.00 atm V 22.4 L T 273 K n 1.00 mol R 0.08206 L·atm mol⁻¹·K⁻¹ P PRESSURE Force per unit area of gas particles. V VOLUME Space occupied by the gas. T TEMPERATURE Average kinetic energy of particles. n MOLES Number of gas particles present. BOYLE'S LAW P vs V · n, T constant INVERSE P ∝ 1/V P V CHARLES'S LAW V vs T · n, P constant DIRECT V ∝ T V T AVOGADRO'S LAW V vs n · P, T constant DIRECT V ∝ n V n CED ANCHOR · THE TAKEAWAY One equation unifies three relationships: Boyle (P–V), Charles (V–T), Avogadro (V–n). REMEMBER Use Kelvin; Pₐ = Xₐ · Ptotal AP Chemistry · Unit 3 · Properties of Substances & Mixtures
The ideal gas law, PV = nRT, ties pressure, volume, amount, and temperature together. Rearrange it to solve for any one variable — but temperature must always be in Kelvin, and the direct and inverse relationships (P with V, P with T) must be kept straight.
PV = nRT Playground · Open the sandbox →

The traps are procedural: mixing up which variables move together (raising T at fixed volume raises P), and plugging temperature in Celsius, which ruins any ratio. Convert to Kelvin first, then let the equation tell you the direction.

The work

3 ways in · any order
Lesson
Ideal Gas Law ›

PV = nRT relates all four gas variables; the relationships and the Kelvin requirement are where students slip. The lesson rearranges the law and tracks direct vs inverse behavior, then closes with a ten-scenario check.

Skill check · 10 scenarios
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Diagnostic
10-item topic check ›

Ten items spanning the Topic 3.4 misconceptions: gas-law relationships misapplied (direct vs inverse), and temperature ratios attempted without converting to Kelvin.

Not started · 10 items · ~15 min
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Targeted Practice
Drill a single misconception ›

Pick one of the failure modes you missed and drill it on its own. The round is adaptive: two correct in a row clears the misconception and moves you to the next.

Take the diagnostic to identify your misconceptions
Diagnostic first