solubily color of Table 6 white colorless white colorless colorless lead(I) oxal
ID: 1058398 • Letter: S
Question
solubily color of Table 6 white colorless white colorless colorless lead(I) oxalate colorless no colorless lead(l) sulfate suitine white colorless magnesium carbonate white colorless colorless hydroxide white colorless magnesium white colorless iodate yes colorless iodide white no colorless magnesium yes colorless yes colorless yes colorless magnesium oxalate white no colorless magnesium sulfate yes colorless yes colorless no colorless magnesium sulfite yes colorless nickel (ll) carbonate green barium iodate green no colorless nickel(II) chloride green white no colorless nickel(ll hydroxide green green yes no colorless nickel (ll) iodate barium sulfite green-black yes green iodide nickel light green yes green yes colorless nickel (I) oxalate no colorless nickel(ll) sulfate green white no colorless nickel sulfite white green um iodate colorless potassium iodide white colorless calcium sultate sodium carbonate colorless. sodium chloride colorless cobalt(TI) carbonate no colorless sodium hydroxide yes colorless cobalt chloride cobalt hydroxide sodium oxalate cobalt(I) iodate rose-red no colorless sodium sulfate cobalt(I) iodide blue-violet yes pink sodium sulfite Colorless Colorless white yes Colorless cobalt(I) oxalate strontium white chloride White no colorless yes colorless strontium hydroxide white strontium iodate copper() carbonate blue no colorless copper(I) chloride blue-green yes blue white strontium iodide yes colorless white strontium oxalate ooppertN) iodate Colorless white strontium sulfate no Colorless white blush white no strontium no color less zinc carbonate blue no colorless zinc chloride white lead(II) carbonate white colorless colorless zinc hydr zinc iodate lead(l) chloride white yes colorless yes colorless white lead(ll) iodide zinc oxalate zinc sulfite White WhiteExplanation / Answer
1) To determine whether or not Pb2+ present in water sample suspected to contaminated with Pb2+ ion leached from lead solder is used to join copper plumbing
Experiment-
i. In a 250 mL beaker, add about 125 to 150 mL of tap water and 3 boiling stones.
ii. Gently boil this solution down to about 15 to 20 mL for tap water.
iii. When the water level reaches about 50 to 75 mL, a white residue on the sides of the beaker may appear. This is an undesirable effect so two actions must be taken.
iv. If solids begin to appear as the water is boiling then extract about 5 to 10 mL of the concentrated water into a clean 50-mL beaker then
v. Add about 3 drops of dilute nitric acid to the water in the 250 mL beaker. The acid will re-dissolve the solids back into the water. Stir well after adding the nitric acid. If the solids remain, add a couple more drops of acid, the solution should be slightly acidic to avoid precipitation of hydroxides and other compounds. Remove the flame. Allow the concentrated solution to cool to room temperature.
vi. Divide solution in two test-tube.
i) THE TEST FOR LEAD
In test-tube 1 add 2ml 0.05 M lead (II) nitrate
To test tube 1 add 4 drops of 6M HCl. Again if a solid does not appear add 4 more drops.
Lead nitrate reacts with HCl to form the insoluble lead chloride, which appears as the white precipitate.
Pb (NO3)2 + 2HCl = PbCl2 + 2HNO3
The insoluble lead chloride reacts with excess Cl- ions to form a soluble complex, the tetrachloro plumbate (II) ion.
PbCl2 + 2HCl -----> 2H+ + PbCl4-2
ii) Repeat this test with water sample in test-tube 2. If a solid does not appear by 10drops then the amount of lead in sample is too small to be detected by this method of analysis. It is probably safe to assume that the amount of lead found in sample is below the maximum contaminant level.
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