4. You have been employed by a local manufacturing company. In the back of an ol

Question

4. You have been employed by a local manufacturing company. In the back of an old shed on the property you find a 10 L bottle containing some solvent mixture. On picking up a 2 gallon bucket of water off the shed floor, you stumble and knock over a mop which falls and breaks the bottle. You notice the old, tattered label on the bottle reads 60% tetrachloroethene (v/v), 25% trichloroethene (v/v), and 15% 1,1,1-trichloroethane (v/v). You soon begin to smell solvent and so quickly leave the shed closing the door behind you. What is the maximum PCE, TCE, and TCA concentrations [mg/L] in the shed's air space if the shed's air volume is 50 m and the average temperature in the shed is 77 ? what is the final concentration of each chlorinated solvent in the water? How much solvent [LJ is remaining on the floor?

Explanation / Answer

Mole fraction of component i in vapor space = Mole fraction of component i in liquid phase*Saturated vapor pressure of component i/Total Pressure

Asssuming, Room at atmospheric condition only,

=>Total pressure = 1bar=760 mmHg

Volume of component i in liquid phase = Volume fraction of i in liquid phase * Total Volume

Total volume = 10 litre

Mass of component i in liquid phase=Volume of component i in liquid phase*liquid density of component i

Moles of component i in liquid phase=Mass of component i in liquid phase/Molecular weight of component i

Mole fraction of component i = Mole of component i/Total Moles

Volume of room = 50 m3

Air density = 1.225 kg/m3

=> Mass of air in room = 50*1.225=61.25 kg

=> Molecular weight of air = 29 g/mol

=> Number of Moles of air =61.25*1000/29=2112 moles

Mole of component i in vapor space = Mole fraction of component i in vapor space * Number of moles of air (neglected moles of organic component because they are very few in comparison to air)

Concentration of component i in vapor space in mg/litre = Moles of component i in vapor space*Molecular weight of component i*1000/50*10^-3

Concentration of component i in water = solubility of component i in water (solubility of organic compounds is very less to affect the total volume)

Solvent remain on floor = Initial Solvent amount - solvent loss in air-solvent loss in water

Solvent in water, kg = solubility in water*Total volume of water(litre)*10^-6

Total water volume = 2 gallon = 7.7 litre

(Note for Trichloroethene and 1, vapor moles from mole fraction coming out to be more than available in liquid phase, so whole mass will be evaporated to vapor space and nothing will remain on floor and in water )

Component Molecular weight, g/mol liquid density, Kg/m3 @77F Saturated Vapor Pressure, mmHg @77F Solubility in water, mg/litre @ 77F Tetrachloroethene 167 1590 5.95 2900 Trichloroethene 131 1460 100 1000 1,1,1 Trichloroethane 133 1320 124 1300

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