Answer:
79 extractions
Explanation:
An<em> isooctane/water partinioning constant</em> of 12/1 means that 12 out of 13 parts of the Pb²⁺ complex will be found in isooctane, while the remaining 1 out of 13 part will remain in water.
- 12/13 * 100 = 92.3% of the Pb²⁺ will be removed with each extraction.
Now we <u>convert 1.4 mg/mL to ug/mL</u>:
- 1.4
= 140 ug/mL
We're looking to have a final concentration of 0.25 ug/mL, so we can write:
- 140 mg/mL * (0.923)ⁿ = 0.25 ug/mL
Where <em>n</em> is the number of extractions.
We <u>solve for </u><u><em>n</em></u>:
- (0.923)ⁿ = 1.786x10⁻³
- n = ln (1.786x10⁻³) / ln (0.923)
- n = 79