Suppose you have two 1-L flasks, one containing N2 at STP,
the o...

Question

Suppose you have two 1-L flasks, one containing N2 at STP, 
the other containing CH4 at STP. How do these systems compare 
with respect to (c) average kinetic energy of the molecules?

Accepted Answer

Welcome back everyone in this example, we need to compare the mean score speed velocity between oxygen and Krypton at 300 Kelvin. So recall that this symbol here means mean square speed velocity. And we would recall that to calculate this value, we would say that V r M. S is equal to the square root and sorry about that. So it's equal to the square root of three, multiplied by r gas constant, R multiplied by r temperature in kelvin and divided by our molar mass of our gas. And so we want to recall that this big M is molar mass. And we can recognize from our formula that because Mueller masses in the denominator and mean square speed velocity is in the numerator, we have an inverse relationship. So we would say that mean square speed is inversely related to our molar mass of our gas. So this is an inverse relationship. And so what that means is that as our molar mass of our gas is higher or increases the mean square speed of our gas is going to decrease. We're sorry, the mean square speed velocity of our gas will decrease. And so as molar mass decreases, we would say the mean square speed velocity of our gas is going to increase. And so we want to make note of our molar mass of oxygen from our periodic table and we see that that is equal to a value of 32g per mole, Whereas on our product table, when we refer to our molar mass of Krypton, we would see that that is equal to a value of 83.80 g per mole. And so we can determine from these notes that our molar mass of oxygen is less than our molar mass of krypton. And so therefore because oxygen is the one with the lower molar mass, we would say that oxygen will have a higher mean square speed, then krypton, and again, that is due to that inverse relationship that we outlined above. And so for our final answer, we're going to highlight this statement here that oxygen will have the higher mean square speed than krypton because it's the one with the lower molar mass. So this is our final answer to complete this example. I hope that everything I reviewed was clear. If you have any questions, leave them down below and I'll see everyone in the next practice video.

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