8/4/2019 Indicator and Buffers Lab
2/5
Purpose:
The purpose of the lab is to understand the concept of
buffers.
Materials:
- Wellplate- Distilled water
- pH and litmus paper
- NaHCO3
- Straw
- NaOH
- HCl
Procedure:
First, take a wellplate and add 20 drops of the distilled water
into one well. Then, dip
the end of the litmus paper into the substance and record the
color results in a data table. Next
add 20 drops of NaHCO3 solution into another well, and place the
tip of the straw into it and
blow gently for a couple minutes. Now remove the straw and test
it with both indicator papers,
record results in data table (this is now a buffer). Add 5 drops
of NaOH into the distilled water
well used before, and test it again with both indicator papers,
record. Add NaOH, and testing
periodically with pH paper, until the paper is the same color as
from the other solution. Record
the color and drops. Now repeat up until after making the buffer
with clean dry wells. Add 5
drops of HCl into the well containing the distilled water. Test
with both indicator papers and
record resulting colors. Counting the drops, add HCl into the
well containing the buffer solution,
while testing periodically with pH paper, until the color is the
same as the second distilled water
solution. Record the color and number of drops needed in the
data table. Dispose of the
solutions down the drain with water. Throw the strips of
indicator paper in the trash, then wash
hands if necessary.
Data:
D-H2O NaHCO3 d-H2O + NaOH NaHCO3+NaOH
# of drops 20 20 5 17
pH 7 9 13 13
Color of U.I. green Blue-green purple purple
D-H2O NaHCO3 d-H2O + HCl NaHCO3 + HCl
# of drops 20 20 5 17
pH 7 9 2 2
Color of U.I. green Blue-green red red
8/4/2019 Indicator and Buffers Lab
5/5
Conclusion/Discussion:
The results of the lab were expected and considered a success.
Although, at the
beginning the buffer had to be re-synthesized as it was believed
that the U.I. would not act properly
additional substances were added, such as the distilled water.
Therefore the buffer was remade which
took roughly 3 minutes of lab time, which was seen as a minor
setback, and the rest of the lab was done
without incident.
Questions:
1. I think the purpose of blowing through the straw into the
NaHCO3 was to add CO2 tothe solution, to make it a buffer.
2. The buffer did work as intended, as it took more drops of
NaOH and HCl to change thebuffers pH than it did for distilled
water to change, thus making the buffer more
resilient than the water.
3. The water took about 5 drops of NaOH to change, whereas the
NaHCO3took about 17.
This difference exists because the NaHCO3 was acting like a
buffer, being less
susceptible to change in pH.
4. The water took about 5 drops of HCl to change whereas the
NaHCO 3 took 17, theexact same amount as the NaHCO3 in the first
test. This difference in drops exists
because the buffer was working, being more resilient to change
in pH than the
distilled water.
5. HCO3- + OH- yield H2O4C6.
