1) The EPA\'s secondary standards for contaminants that may cause cosmetic or ae
ID: 572585 • Letter: 1
Question
1) The EPA's secondary standards for contaminants that may cause cosmetic or aesthetic effects in drinking water suggest an upper limit of 250 mg/L for sulfate ion. If 2.81×104 liters of water in a storage tank contains 26.4 grams of SO42-, what is the contaminant level in ppm? Is this level acceptable based on EPA guidelines?
______ppm ________(acceptable or not acceptable)
2) A sample of an industrial waste water is analyzed and found to contain 12.5 ppb Cr3+. How many grams of chromium could be recovered from 1.02×103 kg of this waste water?
________grams Cr
Explanation / Answer
1)
mass of SO42- = 26.4 g
moles of Zn = 26.4 / 96.06 = 0.2748 mol
volume of water = 2.81 x 10^4 L
concentration = mass / volume
= 26.4 / 2.81 x 10^4 L
= 9.395 x 10^-4 g/L
= 0.940 mg /L
concentration = 0.940 ppm
yes , this level is acceptable. because this is less than 250 mg/L
2)
concentration = 12.5 ppb
= 0.0125 ppm
= 0.0125 mg / L
1 kg --------------> 0.0125 mg
1.02 x 10^3 kg --------------> ??
mass of Cr = 12.75 mg
= 0.01275 g Cr
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