How to Calculate Air Concentration

QUESTION 1

Perform the following calculation for air concentration. Sulfuric Acid: 2.5 mg/m 3  = ____ ppm

Concentration in ppm = 24.45 × mg/m 3 ÷ molecular weight

Molecular weight Sulfuric acid (H 2 SO 4 ) = (1.01×2) = 2.02

(32.06×1)=32.06

(16.00×4)=64.00

2.02+32.06+64.00=98.08moles/gram

1mole=1gram =98.08g (molecular weight)

24.45 × 2.5mg/m 3 ÷ 98.08g = 0.62ppm

QUESTION 2

Perform the following calculation for air concentration. Benzene: 3.0 ppm = ____ mg/m 3 

Concentration in mg/m 3 = molecular weight × concentration (ppm) ÷ 24.45

Molecular weight Benzene (C 6 H 6 ) = (12.011 × 6) = 72.066

(1.008 ×6) = 6.048

72.066 + 6.048 = 78.11moles/gram = 78.11g (molecular weight)

78.11 × 3.0 ÷ 24.45 = 9.58mg/m 3 

QUESTION 3

Perform the following calculation for air concentration. Formaldehyde: 4.0 mg/m 3  = ____ ppm

Concentration in ppm = 24.45 × mg/m 3 ÷ molecular weight

Molecular weight for Formaldehyde (CH 2 O) = (12.011 ×1) = 12.011

(1.008 × 2) = 2.016

(15.999 ×1) =15.999

12.011 + 2.016 + 15.999 = 30.03moles/gram = 30.03g (molecular weight)

24.45 × 4.0 ÷ 30.03= 3.26ppm

QUESTION 4

Perform the following calculation for air concentration. Acetone: 42.0 ppm = ____ mg/m 3 

Concentration in mg/m 3 = molecular weight × concentration (ppm) ÷ 24.45

Molecular weight for Acetone (C 3 H 6 O) = (12.011 × 3) = 36.033

(1.008 × 6) = 6.048

(15.999 ×1) =15.999

36.033 + 6.048 + 15.999 = 58.08moles/gram = 58.08g (molecular weight)

58.08 × 42.0 ÷ 24.45= 99.77mg/m 3 

References

Terrie K. Boguski, P.E. (2006). Understanding Units of Measurement 

https://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.files/fileID/14285 

https://www.ptable.com/#Writeup/Wikipedia