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Temperature and mass density

  • Thread starter jmb07
  • Start date
27
0
Average molecular mass of air is 29 u. What is the mass density of air at 1 atm and -50 degrees celsius??

This is what i have so far....

V=(NkT)/P so V= [(29u)(1.38E^-23)(-50 + 273)]/ 1 = 8.9 x10^-20

The mass is equal to 29u x (6.022 x 10^23) =1.75 x 10^25

density =m/v so = 1.96 x 10^44..........and that is wayyyy off! The correct answer is like around 1, 2, or 3....i need some help. What am i doing wrong?
 

Mapes

Science Advisor
Homework Helper
Gold Member
2,592
17
Try carrying your units through your equations. What does it mean to have a molecular mass of 29?
 
27
0
uh...i know i could try to convert the 29u to (number of atoms)...but i dont have any molecular weight
 

Mapes

Science Advisor
Homework Helper
Gold Member
2,592
17
29u tells you something about the relationship between mass (which is connected to density) and the number of moles (which is connected to the ideal gas law that you're using).
 

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