Thermodynamic- Internal energy of dry air

[harman12345]

Homework Statement

a) what is the density of dry air when the surface pressure is 1010hPa and the temperature is 27°C.

b) what is the internal energy of 1kg of dry air under these conditions?

Homework Equations

P=p*R*T where P is pressure and p is density.

The Attempt at a Solution

a) p = RT/P by solving it gives me
[287*(273+27)] / 101000 => 0.852kg/m

can someone please check what i did for part (a) is right or not?

b) i don't really get where to go with this question. So some help would be really appreciated thanks!

 

[ehild]

Homework Equations

P=p*R*T where P is pressure and p is density.

The Attempt at a Solution

a) p = RT/P

Think it over...

ehild

 

[harman12345]

Think it over...

ehild

OH my bad! should be p=P/RT right?

and hint for part b please

 

[ehild]

The internal energy of the ideal gas is the kinetic energy -both translational and rotational- of its molecules. You must have learned about it. For an ideal gas, it is U=c_vmT, where c_v is the specific heat capacity at constant volume.

http://www.ohio.edu/mechanical/thermo/property_tables/air/air_Cp_Cv.htmlehild