Which of the following best explains why a graph of pressure versus temperature for…
PHYSICS · Single correct · AP · Physics 2: Algebra-based · Thermodynamics · Thermodynamics
Problem
Which of the following best explains why a graph of pressure versus temperature for an ideal gas held at fixed volume is linear and intersects the temperature axis near –273 °C?
(a) Pressure is inversely proportional to the absolute temperature, so a plot of P versus T is a straight line sloping downward toward −273∘C.
(b) As the gas cools some molecules condense, causing n in PV=nRT to decrease at a constant rate with temperature, which makes P fall linearly to zero at −273∘C.
(c) Because P=VnRT for an ideal gas, pressure is directly proportional to the absolute (Kelvin) temperature; extrapolating the straight line to P=0 gives T=0K, which is −273∘C.
(d) Intermolecular attractive forces exactly cancel the gas pressure at −273∘C, so extending the linear decrease in pressure meets the temperature axis there.