Question

2. Calculate the absolute humidity, relative saturation, and dew-point temperature of a mixture of benzene-nitrogen at a pressure of 1.5 bar and temperature of 320 K if the partial pressure of benzene in the mixture is 0.2 bar. (3.0 Points)

Answer 1

Partial Pressure of Benzene = 0.2 bar = (0.2 $\times$ 100) = 20 Kpa ( 1bar = 100 Kpa)

Total Pressure of the mixture = 1.5 bar = (1.5 $\times$ 100) = 150 Kpa

At 320 K temperature Vapour pressure of benzene = 32.07 Kpa

Relative Humidity = Partial Pressure of Benzene / Vapour Pressure of the mixture

= 20 / 32.07 = 0.623

Mixture of Benzene - nitrogen

Mass of benzene = partial pressure of benzene($_{}$$p_{b}$) $\times$ Molecular weight of benzene($M_{b}$) / RT

= 20 $\times$ 78 / 8.314 $\times$​​​​​​​ 320

= 0.586360

= 586.360 Kg

Mass of Nitrogen = (( Total pressure(P) - Pressure of benzene($P_{B}$) ) $\times$​​​​​​​ Molecular weight of nitrogen ($M_{n}$) / RT) $\times$​​​​​​​ 2

= (( 1.5 $\times$​​​​​​​ 101325 - 20000) $\times$​​​​​​​ 14 / 8.314 $\times$​​​​​​​ 320)) $\times$​​​​​​​ 2

= 1389.08 Kg

Absolute Humidity = Mass of benzene / Mass of Nitrogen

= 586.360 Kg / 1389.08 Kg

= 0.42428

DEW POINT temperature calculate by DEW POINT TEMPERATURE VS AIR TEMPERATURE GRAPH

ANSWER PF DEW POINT TEMPERATURE = 308.4 K