ConceptThermodynamics
← All conceptsIdeal gas
equation of state PV/T=const (PV=nRT), isothermal (P~1/V hyperbola)/isobaric (V~T)/isochoric (P~T) processes and their P-V, P-T, V-T graphs, Kelvin-vs-Celsius conversion in ratios
10 ways this goes wrong. Each one is a named misconception the questions are built to catch.
- Boyle/Charles relation invertedTreats pressure as proportional to volume (Boyle) or volume as inversely proportional to T (Charles), inverting the dependence.→
- Charles extrapolation to 0 ignoredIgnores that an ideal-gas volume extrapolates to zero only at absolute zero (not 0 Celsius), mishandling the proportional reasoning.→
- Combined law with changing amountApplies p1V1/T1=p2V2/T2 while gas is added, leaked, or removed, violating the fixed-n requirement.→
- Gas law uses CelsiusSubstitutes Celsius temperature into a gas-law ratio where absolute (Kelvin) temperature is required, so a ratio like T2/T1 is wrong.→
- Iso-process conditions confusedConfuses isothermal, isobaric, and isochoric processes, e.g. holds pressure constant in an isothermal change.→
- Isotherm drawn as straight lineDraws an isothermal P-V process as a straight line instead of a P~1/V hyperbola.→
- P-V/P-T process path misreadMisidentifies which curve or line on a P-V, P-T, or V-T diagram is isothermal vs isobaric vs isochoric.→
- PV=nRT rearranged wrongSolves the equation of state incorrectly for the target variable, e.g. P=nRTV or T=PV/(nR) mis-placed.→
- V-T line origin set at Celsius zeroReads the isobaric V-T (or isochoric P-T) straight line as passing through 0 Celsius instead of extrapolating to absolute zero.→
- pV constant regardless of THolds pV constant during heating at fixed amount, ignoring that pV is proportional to absolute temperature.→
