# Homework Help: Mass of earths atmosphere

1. Sep 25, 2010

### chem1guy

1. The problem statement, all variables and given/known data

above each square ince of the earths surface is 14.7 pounds of air. the density of air at sea level is 1.27g/l. the earth is 7930 miles in diameter and has a mass of 5.98x10^24kg.

use this data to determine the mass in kg of the earths atmosphere

determine the average density in g/mm

2. Relevant equations
4pieR2

3. The attempt at a solution
14.7 lb air/in2 x 1kg/2.205lb x (39.37in/1m)2=1.03x10'4/m2 air above surface
then
A=4pieR2=1.97x10'8mi2 x (1km/.6214)=5.11x10'14m2

then multiply the answers for 1.534x1017kg

is that close for the "a" part?

thanks

Last edited: Sep 26, 2010
2. Sep 25, 2010

### D H

Staff Emeritus
No.

Note: the "pounds" per square inch is a unit of force, not mass.

3. Sep 26, 2010

### chem1guy

sorry typed it wrong. i reposted my work. i don't know where else to go

4. Sep 26, 2010

### D H

Staff Emeritus
I'll be a bit more explicit in where you went wrong.

The "pounds" in "pounds per square inch" is a unit of force, not mass. Your mistake results from assuming it is a unit of mass.

5. Sep 26, 2010

### chem1guy

ok thanks. i'll try to look up the difference b/c we have not covered this distinction in class

6. Sep 26, 2010

### chem1guy

14.7psi x 702771g/m2 x 1kg/1000g= 10331kg/m2 of air above surface
A=4pieR2=1.97x10'8mi2 x (1km/.6214)=5.11x10'14m2 surface area

5.29x10'18 mass of atmosphere!?

7. Sep 26, 2010

### D H

Staff Emeritus
Looks good, but where did you come up with 702771g/m2?

8. Sep 26, 2010

### chem1guy

I looked it up the conversion. I thought it might be in the problem but I can'tseem to find it working backwards

9. Sep 26, 2010

### chem1guy

Volume of a sphere?? Does it have to do with density