- #1

johns123

- 34

- 0

## Homework Statement

At altitude of 160 km, the density of the air is 1.5 x 10^-9 kg/m^3

also the temp at that altitude is 500 K ( that's what it says! )

What is the pressure at that altitude?

## Homework Equations

pV = nRT and mass density of air = "rho"

the 1-values are at STP, the 2-values are at altitude

p1 = 1ATM ; rho1 = 29 kg/m^3 ; T1 = 273 K

And I don't see that either vol or temp is being

held constant, so just Boyle's or Charle's law

cannot apply alone ( in my opinion ).

## The Attempt at a Solution

I think I can establish a ratio between these values at altitude

and the same values at STP and calc the unknown p2. Do you agree?

p1 * V1 n1 * R * T1

_______ = ___________ Where the Rs cancel

p2 * V2 n2 * R * T2

so p2 = p1 [ ( n2 V1 T2 ) / ( n1 V2 T1 )

but ( n2/V2 ) / (n1/V1) should equal ( rho2 / rho1 )

giving p2 = p1 * ( rho2/rho1 ) * T2/T1