According to the EPA. the maximum contaminant level (MCL) of cadmium in drinking

Question

According to the EPA. the maximum contaminant level (MCL) of cadmium in drinking water is 0.0050 mg/L Convert the MCL of cadmium from milligrams per liter lo parts per billion (ppb) A fanner has recently dug a new well for his property He sends a 10 0 mL sample of the well water to the EPA to be tested for the presence of cadmium What is the maximum amount of Cd (in mug) that can be present in this 10 0 mL sample based on its MCL? Suppose the farmer has rethought his plan and dug a new well on the other side of his property. He sends a new 10 0 ml sample after testing, the EPA determines that the sample of water contains 0 00178 mug/mL Cd. Is the well water safe to consume?

Explanation / Answer

M = 0.005 mg/L of Cd

a)

convert to mg per liter ---> ppb

1 mg/L --> 1 ppm

1 ppm --> 1000 ppb

but we have 0.005 ppm so --- > 1000*0.005 = 5 ppb of Cd

b)

V = 10 ml

max amount of Cd in micrograms

Concnetration = mass/V

mass = C*V

mass =  0.005 mg/L * (10/1000 L) = 5*10^-5 mg in those 10 ml

change to microgram

1000*5*10^-5 = 0.05 micrograms of Cd in those 10 ml

c)

V = 10 ml

C = 0.00178 microgram /ml

its good we have concnetration

C = 0.00178 microgram /ml

change to g/L

C = 0.00178 microgram /ml * 1000 ml /L = 1.78 microgram per liter

change micro gram to mg by x1000

C = 1.78*10^-3 = 0.00178 mg / L

Snice 0.00178 < 0.005, it is SAFE to consume

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