For the molecules of an ideal gas in equilibrium, which of the following quantities has an average value of zero?

Step-by-step solution

For an ideal gas in thermal equilibrium, the molecules are in continuous random motion in all possible directions. Since velocity is a vector quantity and all directions of motion are equally probable, the average velocity of the gas molecules is zero ( v = 0 ). Momentum is the product of mass and velocity ( p = m v ). Since the average velocity is zero, the average momentum of the gas molecules is also zero. Speed, density, and kinetic energy are scalar quantities and are strictly positive for a gas in equilibrium