A small amount of the radioactive isotope was mixed with a quantity of a non-radioactive...

A small amount of the radioactive isotope was mixed with a quantity of a non-radioactive lead salt containing 0.0100 g lead (Ar = 207). The whole sample was dissolved in aqueous solution and lead(II) chromate (PbCrO4) was precipitated by the addition of a soluble chromate salt. Evaporation of 10 cm3 of the supernatant liquid gave a residue having a radioactivity of 4.17 × 10–5 that of the original quantity of Calculate the solubility of lead(II) chromate in mol dm–3.