A barium sulfate precipitation titration described at the opening of this chapter is shown in the figure. The initial concentration of Cl^- before adding BaCl₂ was 0.000 19 M in 25 mL of aqueous extract of Martian soil. At the end point, when there is a sudden rise in Ba²⁺, [Cl^-] = 0.009 ±M.

(a) Write the titration reaction.
(b) How many mmol of BaCl₂ were required to reach the end point?
(c) How many mmol of SO₂^{4 -} were contained in the 25 mL?
(d) If SO 24 ^- is derived from 1.0 g of soil, what is the wt% of SO24-in the soil?

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-1.0 Leaching solution added CI" calibration solution added -2.0 Soil added and BaC, begins to enter cell C = 0.009 6 M -at end point- -3.0 = 0.000 19 M before BaCl, addition Ba2+ -4.0 End point -5.0 Lo-0 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 log (concentration, M)