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CAIE
15. Ideal gases
15.1 The mole
- understand that amount of substance is an SI base quantity with the base unit mol
- use molar quantities where one mole of any substance is the amount containing a number of particles of that substance equal to the Avogadro constant NA
15.2 Equation of state
- understand that a gas obeying pV ∝ T, where T is the thermodynamic temperature, is known as an ideal gas
- recall and use the equation of state for an ideal gas expressed as pV = nRT, where n = amount of substance (number of moles) and as pV = NkT, where N = number of molecules
- recall that the Boltzmann constant k is given by k = R/NA
15.3 Kinetic theory of gases
- state the basic assumptions of the kinetic theory of gases
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explain how molecular movement causes the pressure exerted by a gas and derive and use the relationship pV = 1/3Nm
, where is the mean-square speed (a simple model considering onedimensional collisions and then extending to three dimensions using 1/3 = is sufficient) - understand that the root-mean-square speed cr.m.s. is given by < > c 2
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compare pV = 1/3Nm
with pV = NkT to deduce that the average translational kinetic energy of a molecule is 3 – 2 kT