Determination of the K sp of a Slightly
Soluble Compound
Chemistry Lab 117.005
Jimmesia Jones
April 12,2021
, Purpose
The goal of this lab was to learn how to calculate the solubility of a compound (base) by titrating
it with a strong acid. Titrations are when an acid and a base are mixed to produce a salt and
water, which can help to determine the molarity of the acid or the base. This is done by
completing the titration, using provided values to find the molarity of hydroxide ions, then use
that to find the solubility product.
Procedure
Part I: Preparing the Buret
- Obtain three (3) 125 mL Erlenmeyer flasks, two100- to 250- mL, a buret (25mL is best, a 50mL
will work), a ring stand, buret clamp, a stir bar, and a stir plate
- Use one of the beakers to obtain 50 mL of 0.050 M HCl. Use a portion of this HCl solution to
rinse your buret. Be certain to allow the HCl to drain through the stopcock and tip.
- Fill the buret to the 0.00 mL mark. Note the starting volume in your lab notebook
Part II: The Titrations
- Use a volumetric pipet to transfer 20.00 mL of saturated Ca(OH )❑2 solution into each of the
three (3) Erlenmeyer flasks.
- Add 5 drops of phenolphthalein to each flask and swirl. The solution should be a hot pink.
- Rinse the stir bar thoroughly with water and then place it into one of the flasks. Adjust the stirring
rate to achieve smooth stirring.
- Begin the titration. You will notice the pink color beginning to dissipate (go away)
- Add no more than ~ 1 mL at a time. Be careful, the endpoint will come suddenly. When the pink
color disappears completely, the titration is completed.
- Record the final reading on the buret. The contents of the flask can be discarded by pouring down
the drain
- Retrieve the stir bar and wash it thoroughly with water, then place it in the next flask to be titrated
and adjust the stirring rate
- Record the initial buret reading and then begin the second titration
- If you were careful with your first titration, you can rapidly add to within 1 to 2 mL of the volume
of HCl required and then slow the addition of HCl to drop wise to complete the titration
- Record the final reading on the buret
- The contents of the flask may be discarded by pouring down the drain
- Retrieve and thoroughly rinse the stir bar
- Add the stir bar to the final flask
- Record the initial reading on the buret and then titrate the final flask
- If the readings on the first two titrations were within 0.1 mL of each other, you may rapidly add
HCl to within 1 mL of the projected volume. Slow the addition to drop wise and finish the
titration.
- Record the final volume reading on the buret
Clean Up
- All solutions may be disposed of by pouring down the drain. Thoroughly rinse the flask and
beakers with water. Dry the flask and beakers and return them to their appropriate storage
locations. Rinse the buret thoroughly with water and return it to its storage location. Rinse the stir
bar, dry it, and return it to storage. Return the stir plate to its cabinet.
Soluble Compound
Chemistry Lab 117.005
Jimmesia Jones
April 12,2021
, Purpose
The goal of this lab was to learn how to calculate the solubility of a compound (base) by titrating
it with a strong acid. Titrations are when an acid and a base are mixed to produce a salt and
water, which can help to determine the molarity of the acid or the base. This is done by
completing the titration, using provided values to find the molarity of hydroxide ions, then use
that to find the solubility product.
Procedure
Part I: Preparing the Buret
- Obtain three (3) 125 mL Erlenmeyer flasks, two100- to 250- mL, a buret (25mL is best, a 50mL
will work), a ring stand, buret clamp, a stir bar, and a stir plate
- Use one of the beakers to obtain 50 mL of 0.050 M HCl. Use a portion of this HCl solution to
rinse your buret. Be certain to allow the HCl to drain through the stopcock and tip.
- Fill the buret to the 0.00 mL mark. Note the starting volume in your lab notebook
Part II: The Titrations
- Use a volumetric pipet to transfer 20.00 mL of saturated Ca(OH )❑2 solution into each of the
three (3) Erlenmeyer flasks.
- Add 5 drops of phenolphthalein to each flask and swirl. The solution should be a hot pink.
- Rinse the stir bar thoroughly with water and then place it into one of the flasks. Adjust the stirring
rate to achieve smooth stirring.
- Begin the titration. You will notice the pink color beginning to dissipate (go away)
- Add no more than ~ 1 mL at a time. Be careful, the endpoint will come suddenly. When the pink
color disappears completely, the titration is completed.
- Record the final reading on the buret. The contents of the flask can be discarded by pouring down
the drain
- Retrieve the stir bar and wash it thoroughly with water, then place it in the next flask to be titrated
and adjust the stirring rate
- Record the initial buret reading and then begin the second titration
- If you were careful with your first titration, you can rapidly add to within 1 to 2 mL of the volume
of HCl required and then slow the addition of HCl to drop wise to complete the titration
- Record the final reading on the buret
- The contents of the flask may be discarded by pouring down the drain
- Retrieve and thoroughly rinse the stir bar
- Add the stir bar to the final flask
- Record the initial reading on the buret and then titrate the final flask
- If the readings on the first two titrations were within 0.1 mL of each other, you may rapidly add
HCl to within 1 mL of the projected volume. Slow the addition to drop wise and finish the
titration.
- Record the final volume reading on the buret
Clean Up
- All solutions may be disposed of by pouring down the drain. Thoroughly rinse the flask and
beakers with water. Dry the flask and beakers and return them to their appropriate storage
locations. Rinse the buret thoroughly with water and return it to its storage location. Rinse the stir
bar, dry it, and return it to storage. Return the stir plate to its cabinet.
