I. Discuss titration of HCl with NaOH. (watch video)YouTube Vide
the general reaction
using phenolphthalein, moles of acid = moles of base
M, V, moles calculation
Discuss lab directions:
The NaOH is known to be 0.050M. HCl is approximately .05M, but the actual is unknown.
Add approximately 50mL of HCl to a small beaker to take to your lab station. Using 10.00mL HCl will allow for straight forward and simple calculations. Add a bit of HCl to a 10.00mL pipet, 'swish' it back and forth, and allow it to run down the drain. This assures the pipet is not contaminated. Use a pipet to add a 10.00mL aliquot to a 250mL (or slightly larger) Erlenmeyer flask.
Add three drops of phenolphthalein indicator.
Add enough DI water to the flask that the reaction will have "room" to work.
***Note: The DI water added is just water. It has absolutely no impact on the acid/base reaction. And it does not impact the volume of acid or base that you add, therefore it does not affect the moles of acid or base. It's just "filler."
Add a stir bar to the Erlemeyer flask. Place on the stir plate and turn it on so that a gentle stirring happens.
Add a bit of NaOH to your buret, 'swirl' it, and let it empty by opening the stopcock. This assures that the buret (and tip) are not contaminated. Fill your buret with 0.050M NaOH. Record your Vi.
Titrate the HCl with the NaOH. Once the slight pink color stays for 30 seconds or so (check with Mr. Hollis), record your Vf. Calculate deltaV.
Perform three "good" trials. Ask for Mr. Hollis's approval after each trial so he can check your indicator color and look at the volume of base added.
Clean-up: everything down the drain with lots of water. Rinse everything with water and then with DI water.
BUT FIRST: CLEAN YOUR GLASSWARE!!!
Use a little bit of soap, a brush, and lots of water to clean your buret, Erlenmeyer flask, and beaker. Do a final rinse with DI water. Rinse your pipet with DI only. DO NOT DRY THE INSIDE OF ANYTHING WITH A PAPER TOWEL.