Acid-Base Titrations: Windex & Vinegar
We can use the property that acids neutralize bases in order to determine the strength of an
acid
or a base. We will use the process of TITRATION, as we did for salinity.
In this experiment we will split the class in half. Half the class will analyze the strengths of glass cleaners. These
products contain ammonium hydroxide, which we’ll neutralize with hydrochloric acid. We’ll monitor the reaction
using methyl red as an indicator, which changes from red to yellow when the neutralization is complete and the
mixture turns acidic. [It will look purple-> green because of the blue dye in the cleaners.] The other half will analyze
vinegars, which contain acetic acid. This we can neutralize with sodium hydroxide, with phenolphthalein as the
indicator (it turns from clear to pink). Each team is welcome to add a third glass cleaner or vinegar for a 10%
bonus. Available to the class are 0.1M HCl, 0.5M HCl, 0.1M NaOH, and 0.5m NaOH. This challenge is worth 25
points for the presentation (each half of the class will help me evaluate the other), 10 pts. for a
purpose/procedure/data/calculations check in your lab book, and 10 pts. for a lab quiz.
FOCUS QUESTION:
Is there a significant difference in the strengths of “Windex” and a bargain brand?
Is there a significant difference in the strengths of “white” and “cider” vinegar?
PROCEDURE:
1. Set up a buret with hydrochloric acid or sodium hydroxide
solution. Rinse the buret first with a small amount of the
solution before filling it (discard the rinse solution), and run
enough of the solution out the bottom to remove air bubbles
from the pipet tip. Record the starting level.
2. Pipet 10.0 mL of one of the cleaners or vinegars into a clean
50-125 mL erlenmeyer, and add a “squirt” of the appropriate
indicator.
3. Add the solution to the buret until the first permanent color
change appears. Record the final level of base.
4. Discard the neutralized mixture down the drain and thoroughly
rinse out the erlenmeyer with distilled water.
5. Run enough trials with each type of cleaner/vinegar to be
satisfied with your precision.The level of precision should be
agreed upon by your team before you begin, and recorded.
ANALYSIS:
• Determine your avg. volume of acid including an avg. deviation.
• Use your avg. deviation of volume of acid or base to determine min/max values for
the concentration of base/acid in your product. Convert this to a single value with a
+ deviation for the concentration of each brand.
LAB BOOK:
Title & partner, focus question, hypothesis, procedure, small group data &
calculations, balanced equation for your reaction.
PRESENTATION:
You are presenting to peers who understand the process of titration but not the
specific lab, its goals, or the reactions involved.