We consider the separation of the ammonia - air system by absorption of ammonia into water (see Figure below) . At position z₁, the mole fraction of NH₃ is 3.42 mol % . We assume that ammonia is highly soluble in water, while air is practically insoluble in water . We are given z₂ − z₁ = 2 cm . We assume steady state is established and that the temperature and total pressure are equal to 0 °C and 1 atm . 1) Calculate the molar flux of ammonia in SI units. 2) Deduce the mass flux of ammonia in SI units. Given: The molecular weights of air and ammonia are equal to 28.97 kg/kmol and 17.03 kg/kmol, respectively. .
P=0.198(atm/s)
D
NH3,Air
2
cm
(*DiffusionofNH3throughStagnantAirintoWater*)(*Givendata*)PDAB=0.198*101325*10^-4;(*Pa*m^2/s,convertedfromcm^2*atm/s*)R=8.314;(*Pa*m^3/(mol*K)*)T=273.;(*K,15C*)deltaz=0.02;(*m,z2-z1=2cm*)yA1=0.0342;(*molefractionNH3atz1*)yA2=0.0;(*NH3fullyabsorbedatwatersurface(z2)*)MNH3=17.03*10^-3;(*kg/mol*)
In[]:=
(*Molarflux*)NA=(PDAB/(R*T*deltaz))*Log[(1-yA2)/(1-yA1)];
In[]:=
(*Massflux*)nA=NA*MNH3;
In[]:=
Print["Molar flux N_A = ",NA," mol/(m^2 s)"];Print["Mass flux n_A = ",nA," kg/(m^2 s)"];
Molar flux N_A = 0.00153794 mol/(m^2 s)
Mass flux n_A = 0.0000261911 kg/(m^2 s)