Tekanan uap air murni 25° diketahui sebesar 36 mmHg. Pada suhu yang sama hitunglah: A. Tekanan uap larutan urea 75% (Mr=60) B. Penurunan tekanan uap larutan

P° = 36 mmHg
wt = 75 gram (Mr = 60 gram)
wp = 25 gram (Mr = 18 gram)
P = ...................................?
ΔP = ..................................?

nt = wt/Mr
    = 75/60
    = 1,25 mol
np = wp/Mr
     = 25/18
     = 1,39 mol

Xt = nt/(nt+np)
     = 1,25/(1,25+1,39)
     = 1,25/1,64
     = 0,76
Xp = 1 - Xt
     = 1 - 0,76
     = 0,24

P = Xp.P°
   = 0,24 x 36
   = 8,64 mmHg

ΔP = P° - P
      = 36 - 8,64
      = 27,36 mmHg