4(a) An antacid tablet weighing 3.084g was dissolved and diluted to 100mL in a v

Question

4(a) An antacid tablet weighing 3.084g was dissolved and diluted to 100mL in a volumetric flask. A 25mL aliquot was removed and treated with sufficient 8- hydroxyquinoline to precipitate all of the aluminum and magnesium. After proper collection & drying, this weighed 1.7748g. Another 25mL aliquot of the sample was treated with enough ammonia to precipitate just Al(OH)3. After ignition at 800oC, this precipitate weighed 0.1167g. Calculate %Al and %Mg in the antacid.

(b) What is the ionic strength of a solution that is 0.10M FeCl3 and 0.20M in FeCl2?

Explanation / Answer

b) Given that  0.10M FeCl3 and 0.20M FeCl2

I = 0.5*[c(Fe+3)x z(Fe+3)2 + c(Cl-) x z(Cl-)2 + c(Fe+2)x z(Fe+2)2+ c(Cl-)x z(Cl-)2]

[ c = concentration, z = charge on ion]

= = 0.5*[0.1 x (3)2 + 3*0.1 x 1 + 0.2x(2)2 + 2*0.2x 1]

= 0.5*[0.1*9 + 3*0.1*1 + 0.2*4 + 2*0.2*1]

= 1.2 M

Therefore,

Ionic strength = 1.2 M

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