Illustrated Guide to Home Chemistry Experiments

242 DIY Science: Illustrated Guide to Home Chemistry Experiments

at least 30 seconds. Record the final burette reading as

accurately as possible on line D of Table 13-3. Interpolate

the reading to 0.05 mL or better.

Subtract the initial burette reading from the final

burette reading to determine the volume of 0.1000 M

sodium hydroxide titrant that was required to neutralize

the potassium hydrogen tartrate aliquot. Record that

volume on line E of Table 13-3.

The gram molecular mass of sodium hydroxide is

39.9971 g/mol. Use that value and the actual molarity of

the titrant solution to calculate the number of moles of

sodium hydroxide required to neutralize the potassium

hydrogen tartrate aliquot, and enter that value on line F

of Table 13-3.

Using the number of moles of sodium hydroxide needed

to neutralize the aliquot of potassium hydrogen tartrate

and the volume of that aliquot, calculate the molar

solubility of potassium hydrogen tartrate and enter that

value on line G of Table 13-3.

Calculate the Ksp of potassium hydrogen tartrate, and

enter that value on line H of Table 13-3.

1. If you have not already done so, put on your splash
   goggles, gloves, and protective clothing.


2. To about 150 mL of distilled or deionized water in the
   250 mL beaker, add about 2 g of potassium hydrogen
   tartrate. Allow the salt to dissolve for at least 15 minutes,
   stirring periodically, to ensure that the solution is
   saturated. Record the temperature of the solution on
   line A of Table 13-3.


3. Allow the solution to sit undisturbed for several minutes
   until most of the undissolved material has settled to the
   bottom of the beaker. Carefully filter the supernatant
   liquid through a dry filter paper into a second 250
   mL beaker, trying to keep as much as possible of the
   undissolved solid in the first beaker.


4. Transfer 100.00 mL of the saturated potassium
   hydrogen tartrate solution into the 100 mL volumetric
   flask. Fill the flask to the index line, using a dropper or
   disposable pipette to add the last mL or so, and record
   the volume on line B of Table 13-3. (If you’ve calibrated
   the volumetric flask, as described in Chapter 5, record
   the actual volume that the flask contains rather than the
   nominal 100.00 mL volume.)


5. Discard the remaining potassium hydrogen tartrate
   solution and undissolved potassium hydrogen tartrate.
   Rinse the beaker thoroughly, first with tap water and
   then with distilled water.


6. Pour the contents of the 100 mL volumetric flask into
   the 250 mL beaker. Do a quantitative transfer, rinsing
   the volumetric flask several times with a few mL of
   distilled water and adding the rinse water to the beaker
   to make sure all of the potassium hydrogen tartrate is
   transferred to the beaker.


7. Rinse your 50 mL burette twice with 0.1000 M sodium
   hydroxide, running the rinse solution through the tip and
   into a waste container.


8. Clamp the 50 mL burette in a burette clamp and fill it
   to above the 0.00 mL index line with 0.1000 M sodium
   hydroxide solution.


9. Run solution through the burette until the level drops to
   or slightly below the 0.00 mL index line. Make sure that
   there are no bubbles in the body or tip of the burette.
   Record the initial burette reading as accurately as
   possible on line C of Table 13-3. Interpolate the reading
   to 0.05 mL or better.
   Add a few drops of phenolphthalein indicator solution to
   the beaker of potassium hydrogen tartrate solution, and
   swirl slightly to mix.
   Titrate the potassium hydrogen tartrate solution until
   you reach the endpoint, when the phenolphthalein gives
   the solution a distinct pink coloration that persists for

12.

13.

14.

15.

10.

11.

TABLE 13-3: Determine a solubility product constant, Part II—

observed and calculated data

Item Data

A. Temperature of solution_________._____ °C

B. Volume of sodium saturated

potassium hydrogen tartrate

solution _________._____ mL

C. Initial burette reading _________._____ mL

D. Final burette reading _________._____ mL

E. Volume of 0.1000 M sodium

hydroxide titrant used (D – C)_________._____ mL

F. Moles of sodium hydroxide

required ______.________ mol

G. Molar solubility of potassium

hydrogen tartrate ______.________ mol/L

H. Ksp of potassium hydrogen

tartrate ___________________

PRTII: A NEdETERmI THE kSp of poASSIUT m HydRoGEN
TARTRATE TITRImETRICALLy (voLUmETRICALLy)