My question is why do we lower hg2+ concentration to 0.010% to 0.010 M and how d
ID: 546723 • Letter: M
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My question is why do we lower hg2+ concentration to 0.010% to 0.010 M and how did we get 1 x 10^-6 Please explain thanks liaieler s principle is called the common ion effect. A salt will Common This one of its constituent ions is already present in the solution. if one of it solution. the comm sparation by Precipitation ns can sometimes be used to separate ions from each other. For example, con- containing lead(II) (Pb2+ ) and mercury(1) (Hg·*) ions, each at a concentra- 0010 M. Each forms an insoluble iodide (Figure 6-2), but the mercury(U) iodide is der a solution ylss soluble, as indicated by the smaller value of Kp 1O1 The sm e ss = 4.6 × 10 tpossible to lower the concentration ofHg reactio were smalle by 99.990% by selective precipitation with. 1.0 x 10-6 M without should precipitate, dhout precipitating Pb2+2 We are asking if we can lower [Hgil to 0.010% of 0.010 M g Pb2. Here is the experiment: We add enoughto precipitate 99.990% of Hg l the I reacts with Hg?" and none reacts with Pb .To see if any Pb DEMONSTRATION 6-1 Common lon Effect10.11 wo large test tubes about one-third full with saturated aqueous containing no excess solid. The solubility of KCI is approxi- 37M, so the solubility product (ignoring activity effects Add 1 volume of 6 M HCl(aq) oduced later) isExplanation / Answer
You want to isolate 99.99% Hg2+ ions from the mixture of (Pb2+ and Hg2+) ions.(As no isolation is expected to be 100%)
So, when you do so the percent of Hg2+ that will remain in the solution =100-99.99=0.01%
Thus, of the solution of (Pb2+ and Hg2+) ions, where both pb2+ and Hg2+ are at a concentration of 0.01M, you intend to isolate 99.99% Hg2+ of 0.01M .In other words,you will lower the conentration of Hg2+ to 0.01% of 0.01M,
Mathematically, now the concentration of Hg2+ in the mixture will be no longer 0.01M but (0.01% of 0.01M)=0.01/100 *0.01=0.00001*0.01M=0.0000001=1*10^-6 M (very little Hg2+ remains in the mixture)
As you add I- ions firstly Hg2I2 is precipitated ,and thus Hg2+ is removed from the mixture
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