22. A 250.0 mL sample of aqueous solution contains an unknown amount of dissolve

Question

22. A 250.0 mL sample of aqueous solution contains an unknown amount of dissolved NaCl. Analysis of the solution can use of a precipitation reaction such as the ohe that would result from adding an aqueous solution of PoNOs)2. A. What is the chemical formula of the precipitate? B. Write the net ionic equation for this precipitation reaction. C. The precipitate can be recovered by filtration and then weighed. If the mass of precipitate recovered was 5.428 what was the concentration of Cl- ions in the original solution? grams,

Explanation / Answer

A)

total chemical equation:

Pb(NO3)2 + 2 NaCl -------------------> PbCl2 (s) + 2 NaNO3

formula of precipitate = PbCl2

B)

net ionic equation : Pb+2 (aq) + 2 Cl- (aq) -----------> PbCl2 (s)

C)
Pb(NO3)2 + 2 NaCl -------------------> PbCl2 (s) + 2 NaNO3

                    292.5 g                             278.1g

                      X                                     5.428

         X = 292.5 x 5.428 / 278.1

        X = 5.71 g

mass of NaCl = 5.71

moles of NaCl = 5.71 / 58.5 = 0.0976

volume = 25 mL = 0.025 L

concentration of Cl- = 0.0976 / 0.025

                               = 3.90 M

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