1, find the partial pressure of air at 20 degrees.

P2 (air) V = n (air) RT2

P 1 (air) V = n (air) RT 1

1/ P2 = T 1/T2

P 1 (air) = P2(T 1/T2)

= 80.9 *(293 / 263)

= 90. 13 (kPa)

2. Find the partial pressure of water vapor at 20 degrees.

P total = P (aviation) +P(H2O)

P (H2O) =101.6-90.13 =1.47 9 kPa)

3. Find the mass of water vapor at 20 degrees.

H2O V =[m(H2O)/ 18]RT

m(H2O)= 1 1.47 * 1 * 18/8.3 14 * 293

= 0.085 (gram)