Help please Lead poisoning is particularly insidious because it may result from

Question

Help please Lead poisoning is particularly insidious because it may result from a gradual accumulation of lead ion from an unexpected source. Cases of slow poisoning from lead pigments in unglazed ceramic water vessels are not uncommon. How much lead (AW=207.1), in milligrams, would be ingested by a person drinking 1.00 liter of water a day for 4 years from a ceramic water jug whose ?chrome-yellow? pigment (PbCrO4), unprotected by glaze, has saturated all the water stored in it? (Ksp for PbCrO4 = 1.8 x 10^-14)

Explanation / Answer

Solution :-

Given data ksp of PbCrO4 =1.8E-14

Molar mass of lead = 207.1 g per mol

Person drinking 1 L waterper day for 4 years

Mass of Pb ingested by person = ? mg

Lets write the ksp equation of the PbCrO4

PbCrO4   ---------- > Pb^2+ + CrO4^2-

                                      x               x

Now lets calculate the molar solubility of the PbCrO4 using the ksp vaue

Ksp = [Pb^2+] [CrO4^2-]

1.8E-14 = [x][x]

1.8E-14 = x^2

Taking square root of both sides we get

1.34E-7 = x

Therefore molar solubility of the PbCrO4 is 1.34E-7 mol per Liter

Now lets calculate the total amount of water drunken by the person in 4 years

(4 years * 365 days / 1 year ) *(1 liter / 1 day) = 1460 L

Now lets calculate the moles of the PbCrO4 drunken in 4 years

Moles = molarity * volume in liter

Moles of PbCrO4 = 1.34E-7 mol per L * 1460 L = 1.956E-4 mol

Now lets convert these moles to mass of the Pb^2+ ingested

(1.956E-4 mol * 207.1 g / 1 mol )*(1000 mg / 1 g ) = 40.5 mg Pb

Therefore amount of the lead ingested to person = 40.5 mg

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