Calculate the root mean squared speed for 16g of oxygen gas at 50(deg Celsius) and explain why we use this instead of the average velocity of all the particles.
Root mean squared speed is given by v(rms) = (3kbT/m)^(0.5) = 501.68. Student should show how to calculate the mass of each particle (m = (0.016)/0.5(6.01x10^23)), convert degrees celsius into kelvin and understand that oxygen is a diatomic molecule so there are half as many molecules as with atomic oxygen.The student should show an understanding that the average velocity in three dimensions will often cancel out, giving an average velocity of zero. So to calculate a truly representative average, the average of the squared (and so strictly positive) velocities must be taken and then rooted. This is particularly important in terms of kinetic energy calculations.
JW
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