Can someone please show/explain how to do #8 in the attached picture? Thanks!

1 Answer | Add Yours

llltkl's profile pic

llltkl | College Teacher | (Level 3) Valedictorian

Posted on

Two soluble metal salts react with each other to form one soluble salt and one insoluble salt.  Lead nitrate solution and potassium chloride solution react to produce solid lead chloride, leaving soluble potassium nitrate in solution. The lead chloride can be recovered by filtration and purified through crystallization from water.

The balanced equation for the reaction is:

`Pb(NO_3)_2(aq.) + 2KCl(aq.) rarr PbCl_2(s) + 2KNO_3(aq.)`

Molar mass of `Pb(NO_3)_2` is (207.2+(14+3*16)*2), i.e. 331.2.

Molar mass of KCl is ( 39.1+35.45), i.e. 74.55

So, 1g Pb(NO3)2 is 1/331.2 i.e. 0.003019 moles and 1g KCl is 1/74.55 i.e. 0.003019 moles 0.013414 moles. But Pb(NO3)2 requires 2*0.003019 i.e. 0.006039 moles of KCl. Therefore after the reaction, KCl would remain in excess and Pb(NO3)2 is the limiting reagent here.

Apparatus:

Eye protection

Test-tubes

Rubber stopper to fit test-tube

Beakers (100 cm^3),

Teat droppers

Glass rod (15 cm)

Measuring cylinder (10 cm^3)

Wash bottle with purified distilled water

Filter funnel

Filter paper

Bunsen burner

Tripod stand

Wire Gauze

Heat resistant mat

Chemicals:

Lead(II) nitrate, 1 g (TOXIC, DANGEROUS FOR THE ENVIRONMENT),
Potassium chloride, 1 g,

Procedure:

a. Dissolve 1 g solid Pb(NO3)2 in 3 ml distilled water in a stoppered test tube. The resulting solution is approximately 1 M Pb(NO3)2. Similarly, prepare 2 M KCl solution by dissolving 1 g solid KCl in 6 ml distilled water in another stoppered test tube.

b. Add the KCl solution to the test tube containing lead(II) nitrate solution in small portions and with constant stirring. Copious yellow precipitate of PbCl2 should settle at the bottom of the test tube.

c. Filter the precipitate using a filter paper and filtering funnel. Wash the precipitate by pouring a small amount of distilled water over the residue and allowing it to filter through.

d. Transfer the solid residue to a beaker and add about 30 cm^3of purified water. Heat the suspension in the beaker gently over a mild Bunsen flame, with stirring, until the suspension has dissolved completely. Remove the flame and allow it to cool. Crystals reappear on cooling. They can be collected by filtration and dried on a paper towel.

 (At the end of this experiment, wash your hands thoroughly to remove any toxic lead compounds that may have splashed onto them).

We’ve answered 318,915 questions. We can answer yours, too.

Ask a question