Eshetu 1
Final Lab Report
Chemistry 1212k
Yonatan Eshetu
Lab Group: Tuesday 10am-1pm
Eshetu 2
Table of Contents
Introduction……………………………………………………………………………...pg. 3
Preparation of a Cobalt Amine Bromide Product……………………………………….pg. 3
Preparation of AgNO3 ………………………………………………………………….. pg. 3
Precipitating the Halide………………………………………………………………….pg. 4
Preparation and Standardization of an Approximately 0.3M HCl Solution……………..pg. 5
Analysis of %NH3 Using 0.3M HCl……………………………………………………. pg. 6
Preparation and Standardization of 0.1M Na2S2O3……………………………….......... pg. 7
Analysis of %Co3+ Using Standardized 0.1M Na2S2O3 ……………………………….. pg. 8
Conclusion……………………………………………………………………………… pg. 9
Appendix……………………………………………………………………………….. pg.10
Eshetu 3
Introduction
For the 2013 Fall Semester in Chem 1212K Lab students were given a Cobalt compound,
which they were supposed to identify by the end of the course. I was instructed to create the
compound made through Synthesis Procedure V, which is on page 20 of the lab manual. We
were instructed to carry out several experiments to determine the properties and characteristics of
our compounds. We were also told to document everything that happened in the lab in a
composition notebook, including raw data and calculations. The most important experiments that
I carried out and that will be key components of this report are the Precipitation of the Halide,
Analysis of %NH3, and Analysis of %Co3+. There are a few others, but these three were the most
important as they were used to identify which Cobalt compound I had.
Preparation of a Cobalt Amine Bromide Product

Purpose: The purpose of this experiment was to create our unknown cobalt compound,
mine coming from the instructions presented in Synthesis Procedure V.

Procedure: The procedure for this experiment is found on page 20 of the lab manual.

Data: Used 4.0010g of CoCO3

Discussion/Conclusion: Once formed, the dried solution ended up purple.
Preparation of AgNO3

Purpose: The purpose of this experiment was to prepare the silver nitrate solution that
will be used in the next experiment.

Procedure: The procedure for this experiment is found on page 20 of the lab manual.

Data: Used 1.7454g of AgNO3
Eshetu 4

Discussion/Conclusion: Everything went well in this experiment. It was simple and
straightforward mixing so there was nothing to worry about here.
Precipitating the Halide

Purpose: The purpose of this experiment was to determine the %Cl- or %Br- of our
compound, depending on whether AgCl or AgBr was used.

Procedure: The procedure for this experiment is found on page 20 of the lab manual.

Data:
Crucible A weight: 31.0880g  31.4490 - 31.0880 = 0.3610g
Crucible B weight: 31.0460g  31.4078 – 31.046 = 0.3618g

Mass of Co-
Mass of
% Halide in
sample
Precipitate
Co-sample
A
0.2418g
0.3610g
63.52%
B
0.2440g
0.3618g
63.07%
Calculations: Calculations used include the determination of % halide in Co-compound,
Avgerage % halide, and % Deviation.
o Sample Calculation:
A-
?𝑔𝐵𝑟
0.3610𝑔
=
79.91𝑔 𝐵𝑟
187.8𝑔 𝐴𝑔𝐵𝑟
0.1536g Br in ppt
% = part/whole * 100  %Br =

0.1536𝑔
.2418𝑔
*100% = 63.52% Br
Discussion/Conclusion: I calculated the % halide for sample B using the same format
above. After computing the average % halide as well as the % deviation I found this
compound to be 63.30% halide with a 0.36% deviation.
Eshetu 5
Preparation and Standardization of an Approximately 0.3M HCl Solution

Purpose: The purpose of this experiment was to prepare an HCl solution, about 0.3M,
which would be used in future titrations.

Procedure: The procedure for this experiment is found on page 20 of the lab manual.

Balanced Chemical Equation:
(HOCH2)3CNH2 + HCl  (HOCH2)3CNH3+ + Cl-


Data:
Mass of THAM
Vol of HCl used
Molarity of HCl
Trial 1
0.8170g
0.02360L
0.2859M
Trial 2
0.8636g
0.02490L
0.2864M
Trial 3
0.8169g
0.02340L
0.2883M
Calculations: I used basic calculations in this experiment, including finding the average
molarity and % deviation.
o Sample Calculation (Deviation):
|0.2859−0.2869|+|0.2864−0.2869|+|0.2883−0.2869|
3
=
|.001|+|.0005|+|.0014|
3
=
.0009667 * 100% = 0.09667% ~ 0.1%

Discussion/Conclusion: The third trial listed in my data table is actually my fourth; I over
titrated my third trial giving me a low molarity of 0.2480M, which gave me a 2.017%
deviation. This new trial brought my results down to a 0.1% deviation, within the <1%
range, and an average of 0.2869M, closer to the approximated 0.3M than I had previously
(0.2710M).
Eshetu 6
Analysis of %NH3 Using 0.3M HCl

Purpose: The purpose of this experiment was to determine the %NH3 in our cobalt
compounds.

Procedure: The procedure for this experiment is found on page 20 of the lab manual.

Balanced Chemical Equation:
NH3 + HCl  NH4+ +Cl-

Data:
Mass of
Vol. HCl
Co-compound

%NH3 in Cocompound
Trial 1
0.3646g
0.01620L
21.67%
Trial 2
0.3604g
0.01600L
21.66%
Trial 3
0.3655g
0.01635L
21.83%
Calculations: Aside from the average and %deviation calculations I had to calculate
%NH3, an sample of which I will show below.
o Sample Calculation:
Trial 1- M=Moles/L  moles=M*L  moles= 0.2869M HCl * 0.01620L =
0.004648 moles HCl  0.004648 moles NH3 (b/c of 1:1 ratio)
0.004648 moles*
%NH3 =
.
17.006𝑔
1 𝑚𝑜𝑙 𝑁𝐻3
(𝑔 𝑁𝐻3)(100)
𝑔 𝑠𝑎𝑚𝑝𝑙𝑒
→
= 0.07904g NH3
(0.07904𝑔)(100)
0.3646𝑔
= 21.67%
Eshetu 7

Discussion/Conclusion: After going back and changing the molarity I had for HCl my
average %NH3 rose from 20.52% to 21.72% with a small change in % deviation to 1.0%.
Preparation and Standardization of 0.1M Na2S2O3

Purpose: The purpose of this experiment was to prepare a 0.1M solution of sodium
thiosulfate for a future titration (%Co).

Procedure: The procedure for this experiment is found on page 20 of the lab manual.

Balanced Chemical Equation:
KIO3 + 6HCl + 6Na2S2O3  3Na2S4O6 + KI + 3H2O + 6NaCl


Data:
Mass KIO3
Vol Na2S2O3
Molarity Na2S2O3
Trial 1
0.1083g
0.03005L
0.1010M
Trial 2
0.1029g
0.02915L
0.0990M
Trial 3
0.1054g
0.02960L
0.09984M
Calculations: Average molarity and standard deviation were calculated in this
experiment.
o Sample Calculation (Deviation):
|0.1010−0.0995|+|0.0990−0.09995|+|0.09984−0.09995|
3
= 0.002110 * 100%
= 0.2110%

Discussion/Conclusion: Using the 1:6 ratio between KIO3 and sodium thiosulfate I found
the molarity for each trial. My average molarity for the 3 sodium thiosulfate solutions
Eshetu 8
came out to be 0.09995M and my % deviation was within the allotted range again at
0.2110%.
Analysis of %Co3+ Using Standardized 0.1M Na2S2O3

Purpose: The purpose of this experiment was to

Procedure: The procedure for this experiment is found on page 20 of the lab manual.

Balanced Chemical Equation:
2Co (NH3)4Cl3 + 2S2O32-  2CO2+ + S4O6 + 8NH3 + 6Cl-

Data:
Mass of
Co-Compound
Vol of
%CO in Sample
Na2S2O3 Used in
Titration

Trial 1
0.5167g
0.01380L
15.72%
Trial 2
0.5165g
0.01390L
15.84%
Trial 3
0.5234g
0.01370L
15.41%
Calculations: In addition to the average %Co and standard deviation calculations, I had to
find the %Co for each trial, which is what is shown below.
o Sample Calculation:
Trial 1- ?gCo=0.01380L Na2S2O3 *
0.09995𝑀
1 𝑚𝑜𝑙 𝐶𝑜
*
58.9 𝑔
*
1 𝐿 Na2S2O3 1 𝑚𝑜𝑙 Na2S2O3 1 𝑚𝑜𝑙 𝐶𝑜
*100%
= 15.72%

Discussion/Conclusion: Using the 1:1 ratio between cobalt and sodium thiosulfate I was
able to find the %Co for each trial. My average came out to be 15.66% with a deviation
of 3.13%. I might attribute this high deviation to me moving through this experiment
Eshetu 9
rather quickly; however, all of my titrations turned out nicely as I got the “go-ahead”
from my TA’s so this could just be a normal occurrence.
Conclusion
Data:
% Co
%NH3
%Br (halide)
15.66%
21.72%
63.30%
After completing all the required experiments I went back to the Halide, Ammonia, and
Cobalt experiments to compare my results to the chart presented on page 66 of the lab manual in
order to identify my cobalt compound. Using the averages calculated in each of these three
experiments I declare my compound to be [Co(NH3)5Br]Br2 or compound #7 on the lower chart.
I believe this to be the identity of my compound for several reasons including the specific halide
I added to it and its similar values to the ones stated for [Co(NH3)5Br]Br2.
All of the compounds in the first chart are automatically incorrect because the halide
added to my compound was Bromide (AgBr) not Chlorine. Then there is the closeness my values
for %Co, %NH3, and %Halide have with [Co(NH3)5Br]Br2. Its values for these three respectively
are 15.36%, 22.16%, and 62.48%. From the chart one can see that these values are the closest, as
a whole, to the ones I calculated.There is a small difference between my values and the values
[Co(NH3)5Br]Br2 has, but this is due to human and technological error (e.g. spills, inaccurate
readings, etc.).
Eshetu 10
Appendix

%Yield Calculation:
4.0010𝑔 𝐶𝑜𝐶𝑂3
118.9
𝑔
𝑚𝑜𝑙𝑒
= 0.03365 mol Co2+ used
7.1584 [Co(NH3)5Br]Br2
𝑔
𝑚𝑜𝑙𝑒
383.63
0.018660 𝑚𝑜𝑙 𝐶𝑜
0.03365 𝑚𝑜𝑙 𝐶𝑜
= 0.018660 mol Co3+ recovered
*100% = 55.45% yield of cobalt