CHEM 201 Lecture 13: Chem 201 Lab 4

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19 Feb 2020
School
Department
Course
Professor
Rebecca Tsarofski 3/14/19
Lab Partner: Olivia Mattos
Chem 201 Experiment 4
Titration Curves
Procedure: Refer to page 10 of my lab manual for a breakdown of the general procedure to be
followed. There were no changes made to the procedure. About 175-200 mL of waste were
expected to be produced. The standard NaOH solution had a concentration of 0.09207 M and
my unknown acid # was 3405.
Experimental Data:
Equivalence Point Volume from First Titration
31.30 mL
Equivalence Point Volume from Titration Curve
30.75 mL
Calculated Results
Volume of NaOH added
pH of flask
[base]/[acid]
pK
Kₐ
¼ point
7.69 mL
4.20
4.68
2.10 x 10
½ point
15.38 mL
4.73
1
4.73
1.86 x 10
¾ point
23.06 mL
5.21
3
4.73
1.84 x 10
Discussion:
In this experiment, we carried out two titrations. The first was a test round to see how
much base needed to be titrated with the acid before the solution changed color to pink. Using
this approximated volume of NaOH, my partner and I then carried out the second titration only
using the pH meter to detect changes.
With the C1V1=C2V2 equation, I was able to find the concentration of our unknown acid
to be 0.1132 M. From the titration curve, I used the pH and base/acid ratios to find the Ka
values, which came out to 2.10 x 10, 1.86 x 10, and 1.84 x 10. The Ka value for the original
pH of the acid came out to be 3.58 x 10. These values got progressively smaller as more
NaOH was titrated with the acid, which is what was meant to happen as the solution moved
closer to equilibrium. My NaOH values also seemed to match well. From our first titration, 31.3
mL of NaOH were titrated with our unknown acid. On the titration curve, the equivalence point
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