Lab 10 Procedure

The two steps of the lab are:

  1. Preparation of Chemicals and Glassware
  2. Perform a Titration Reaction

Safety for this lab:

  • Wear safety glasses at all times.
  • ALWAYS clean up your entire station and any spills made at shared stations.
  • DO NOT deposit broken glassware in trash, place into broken glassware container located near paper towels.

THE PROPER NUMBER IF SIGNIFICANT FIGURES WILL BE USED FOR ALL MEASUREMENT RECORDINGS AND ALL CALCULATION ANSWERS.

Preparation of chemicals and glassware

Watch the video for the procedure to set up this lab.

Written Instructions for this part:

  1. Obtain the following chemicals for this lab:
    • Approximately 75 mL of known NaOH (sodium hydroxide) solution into a medium-sized beaker (label this)
    • Approximately 40 mL of unknown HCl (hydrochloric) solution into a small-sized beaker (label this)
    • Dropper bottle of phenolphthalein indicator (do not take this back to your station – needs to be shared)
    • Clean distilled water in distilled water bottle
  2. Obtain the following equipment for this lab:
    • Buret with clamp
    • Ring stand 
    • Long glass funnel
    • Large beaker labeled waste beaker
    • 10 mL pipet with bulb or suction
    • 125 mL erlenmeyer flask

Watch the following video to see how you Prepare the Buret:

Written Instructions for this part:

  1. Attach the buret to the ring stand with the buret clamp.
  2. Place the long glass funnel into the top of the buret.
  3. Put clean distilled water into your distilled water bottle.
  4. Place a large beaker labeled “waste” under the buret and rinse your buret with at least 15 mL of distilled water.
  5. Leaving the waste beaker under the buret, rinse your buret with at least 15 mL of the known NaOH (sodium hydroxide) solution.
  6. After buret is rinsed, close the buret up completely and fill the buret with the known NaOH solution. You do not need to fill the buret completely to the zero mark. You can fill it up any place above the 10mL mark on the buret.
  7. Remove the long glass funnel from the top of the buret.
  8. Carefully record the initial buret reading based upon the location you filled up your buret.

Record on your Data Sheet:

l10_01

Watch the following video to see how you Prepare add the HCl into the Erlenmeyer flask.

Written Instructions for this part:

  1. Using the distilled water bottle, completely rinse your pipet, allowing the water to rinse into your waste beaker.
  2. Using the pipet bulb, suction up the unknown HCl (hydrochloric acid) solution into the pipet and allow this to rinse into your waste beaker.
  3. After pipet is rinsed, suction up the unknown HCl solution into the pipet, exactly to the 10.00 mL mark on the pipet and allow to rinse into a clean 125 mL erlenmeyer flask.

Record on your Data Sheet:

l10_02

Perform a Titration Reaction.

Note: Each Lab Partner is to Perform One Titration

Watch the following Video to see how you Perform the titration. Note: In the video I show this titration quickly. You will want to slow down as the pink color is staying longer with each addition. You can slow down the titration to delivering just drop by drop amounts.

Written Instructions for this part:

  1. Add 2-3 drops of the phenolphthalein indicator to the unknown HCl in the erlenmeyer flask.
  2. Place the erlenmeyer flask under the buret and slowly add the known NaOH solution, swirling the flask as it is adding.
  3. Take times to stop the titration to rinse the inside of the erlenmeyer flask with distilled water from the distilled water bottle, just to rinse down any drips.
  4. Continue to add the known NaOH solution from the buret until a light pink color remains in the erlenmeyer flask for at least 30 seconds while you are swirling.
  5. The titration is complete when the 30 seconds of light pink remains. If you end up with a dark pink you overshot the endpoint which means you added too much NaOH.

Note: the endpoint is reached when one drop of NaOH base turns the entire HCl (acid solution) a faint, light pink.  This color must remain for 30 seconds for it to be a true endpoint. 

Record on your Data Sheet:

l10_03

L10_04.png

l10_05

l10_06

FINAL STEP: CLEAN YOUR STATION 

Use the sinks and soap to wash your glassware.  Perform a final distilled water rinse to all your glassware.

PUT AWAY ALL EQUIPMENT AND CHEMICALS AND WIPE DOWN YOUR STATION.

Do not leave the lab until the instructor has inspected your clean station.

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