Regarding my question on

Question

display.cgi?id=1496901710(I can't post URLs)

Can we apply the formula PM=dRT seperately to the systems before and after being heated,and solve this one?

Answer 1

http://www.jiskha.com/display.cgi?id=1496901710

Answer 2

Thanks to Writeacher for making that link easier to find. At first glance, it appears to me that you can. But why not just run it and see if it comes out the same. I think it will.

Answer 3

I tried that method and got the percentage as 37/5℅ ,which is the given answer.
And also I tried the method you suggested which gave out the answer 49.14℅ as the percentage.

So just wanted to know the reason for the contradiction of the answers I got from the two methods. Did I made a mistake?

Answer 4

*37.5℅

Answer 5

You must have made an error. I ran through both calculations and got the same densities so percent different must be the same.
For O2 PM = dRT gives 1.30 for O2 and 1.79 for CO2.

The first method we used was (but I left the final calculations to you):
O2 = 32/22.4 x 273/300 = 1.30
CO2 = 44/22.4 x 273/300 = 1.79

So I don't see a discrepancy.

Answer 6

There you gave the density of O2 as 1.42*273/300 and density of CO2 as 1.96*273/300
So I calculated it this way (1.96-1.42)*273/300*100℅= 49.14℅

The change in values seems to have made the difference..

Answer 7

And that way calculating it is not right.
O2 is 1.42 x 273/300 = 1.30
CO2 is 1.956 x 273/300 = 1.79(rounded)
[(1.79-1.30)/1.30]*100 = 37.7%

Answer 8

In other words, you calculate the change in density at 273 K instead of change in density at 300 K