Question

A clumsy ENVSE professor accidentally spills a bottle containing 125 mL of m-xylene (CAS 108-383) in a laboratory measuring 12 ft x 15 ft x 8 ft. Assuming that the contents completely evaporate and fill the space, what is the resulting concentration of m-xylene in units of mg/m3 and ppmv assuming NTP? Show your work and explain your reasoning in answering the following:

a. Estimated Concentration, mg/m3 = _______________________________________  
b. Estimated Concentration, ppmv = _______________________________________
c. Is this environment hazardous from a safety (fire and explosion) perspective?  
d. Is this environment hazardous from a health perspective?

Answer 1

125 mL of m-xylene; density =     0.86 g/mL

Therefore mass of m-xylene = 125 mL x 0.86 g/mL
                           = 107.5 g
                         
Now, we have to find volume of the lab in m3 ;
Given dimensions of the lab are: 12 ft x 15 ft x 8 ft
       volume of lab = 1440 ft3
                      = 40.78 m3 (1 cubic ft = 0.028317 cubic m)
Now, we have volume of the lab and mass of the m-xylene,
Therefore,
concentration = mass/volume in m3
              = 107.5 g/40.78 m3
              = 2.636 g/m3
              = 2636 mg/m3
Therfore, a.     Estimated Concentration, mg/m3 =   2636 mg/m3   
b.     Estimated Concentration, ppmv = mg/m3 (RT/M)
                                      = 2636 mg/m3 (0.08205 atm.m3/kmol.K x 293.15 K)/‎106.168 g/mol)
                                      = 597 ppmv
therefore, the answer is : 597 ppmv
c. Is this environment hazardous from a safety (fire and explosion) perspective?
air density (NTP) = 1.2041 kg/m3
That means the mass of air in 1 m3 = 1.2041 Kg = 1204.1 g

we have mass of m-xylene in 1 m3 = 2.636 g

Therefore, the percent of m-xylene present in air =(mass of xylene/mass of air)x 100
                                                  = (2.636 g/1204.1 g)100
                                                  = 0.22 %
The explosive limits of m-xylene is = 1.1% - 7.0%
Therefore, in our case the m-xylene is under the lowest limits of explosion..therefore, there is no possibility of
explosion with this concentration of m-xylene.

d.     Is this environment hazardous from a health perspective?

According to the US, health exposure limits the permissible limit is = 435 mg/m3
Our concentration is 2636 mg/m3 which way too high, hence, there is the serious environmental and health issues are there.