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EXPERIMENT 9: REAL WORLD PROJECT
Risk Assessment Form
Definitions:
H - Hazard
P - Precautions needed
R - Response to Hazard
Ammonium Hydroxide Buffer
H1.1 Inhalation - will damage upper respiratory tract
P1.1 Work in fume hood when using the buffer
R1.1 If inhaled, move person to fresh air
H1.2 Acute Toxicity - harmful if swallowed
P1.2 Wash hands before leaving the lab and eating food
R1.2 Rinse mouth with water, consult a physician
H1.3 Corrosive - will burn skin
P1.3 Wear gloves
R1.3 Remove contaminated clothing, wash affected area with water for 15 minutes
Hydrochloric Acid
H2.1 Inhalation
P2.1 Work in the fume hood
R2.1 If inhaled, move person to fresh air
H2.2 Corrosive - will burn skin
P2.2 Wear gloves
R2.2 Remove contaminated clothing, wash affected area with water for 15 minutes
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EXPERIMENT 9: REAL WORLD PROJECT
Intro:
The purpose of this lab is to look deeper into EDTA titrations by testing the hardness of various tap
water samples. This lab is a recap of Experiment 6, in which EDTA was first standardized, then tested
against an antacid tablet containing Calcium and tap water. The lab helps enhance the understanding of
how EDTA titrations work, and how they react with metals.
Procedure:
A pH meter was calibrated and used to test ammonium buffer. HCl and NaOH would be added to the
ammonium until a pH of 10 was reached. An EDTA solution (~0.01 M) was prepared using 1 g of EDTA, 5
mL of ammonium buffer, and diluting it to 250 mL. A CaCO3 solution (~0.05 M) was prepared using 0.5 g
CaCO3 (s) and dissolved in 100 mL of 0.15 M HCl. The EDTA was then standardized with the CaCO3 with
calagamite indicator. This process was repeated 3 times until good titrations were recorded. For each
source of tap water, 3 x 100 mL samples with 5 mL buffer and calagamite were titrated with EDTA until
good titrations were recorded.
Data:
Refer to Excel Spreadsheet
Calculations:
Mass EDTA
Required
Moles CaCO3
𝑉 𝐸𝐷𝑇𝐴 ∗
0.1 𝑚𝑜𝑙 𝐸𝐷𝑇𝐴 372.24 𝑔 𝐸𝐷𝑇𝐴
∗
1𝐿
1 𝑚𝑜𝑙 𝐸𝐷𝑇𝐴
𝑚𝑎𝑠𝑠 𝐶𝑎𝐶𝑂3 ∗
1 𝑚𝑜𝑙 𝐶𝑎𝐶𝑂3
100.09 𝑔 𝐶𝑎𝐶𝑂3
Molarity
EDTA
𝑉 𝐶𝑎𝐶𝑂3 ∗
𝑚𝑜𝑙 𝐶𝑎𝐶𝑂3
1
∗
1 𝐿 𝐶𝑎𝐶𝑂3 𝑉 𝐸𝐷𝑇𝐴
Concentration
Ca2+
𝑉 𝐸𝐷𝑇𝐴 ∗
𝑚𝑜𝑙 𝐸𝐷𝑇𝐴
1
∗
1 𝐿 𝐸𝐷𝑇𝐴 𝑉 𝑊𝑎𝑡𝑒𝑟
Hardness of
Water (ppm)
𝑚𝑜𝑙 𝐶𝑎 40.078 𝑔 𝐶𝑎 1000 𝑚𝑔
∗
∗
1 𝐿 𝐶𝑎
1 𝑚𝑜𝑙 𝐶𝑎
1𝑔
Spike
Recovery %
[𝐶𝑎2+] 𝑒𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡
∗ 100%
[𝐶𝑎2+] 𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙
0.25 𝐿 ∗
0.1 𝑚𝑜𝑙 𝐸𝐷𝑇𝐴 372.24 𝑔 𝐸𝐷𝑇𝐴
∗
= 1.02𝑔 𝐸𝐷𝑇𝐴
1𝐿
1 𝑚𝑜𝑙 𝐸𝐷𝑇𝐴
0.5024 𝐶𝑎𝐶𝑂3 ∗
1 𝑚𝑜𝑙 𝐶𝑎𝐶𝑂3
= 0.0502 𝑚𝑜𝑙 𝐶𝑎𝐶𝑂3
100.09 𝑔 𝐶𝑎𝐶𝑂3
0.005 𝐿 𝐶𝑎𝐶𝑂3 ∗
0.0502 𝑚𝑜𝑙 𝐶𝑎𝐶𝑂3
1 𝐿 𝐶𝑎𝐶𝑂3
∗
1
=0.0099 M
0.04950 𝐸𝐷𝑇𝐴
EDTA
0.00873 𝐿 𝐸𝐷𝑇𝐴 ∗
0.000994𝑚𝑜𝑙 𝐶𝑎
1 𝐿 𝐶𝑎
0.0099 𝑚𝑜𝑙 𝐸𝐷𝑇𝐴
1 𝐿 𝐸𝐷𝑇𝐴
∗
40.078 𝑔 𝐶𝑎
1 𝑚𝑜𝑙 𝐶𝑎
∗
∗
1
0.1 𝐿 𝑊𝑎𝑡𝑒𝑟
1000 𝑚𝑔
1𝑔
=0.000994 M Ca
=39.85 ppm
63.16
∗ 100% = 59.50% 𝑟𝑒𝑐𝑜𝑣𝑒𝑟𝑦
106.15
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EXPERIMENT 9: REAL WORLD PROJECT
Conclusion:
Overall, the experiment was successful up to the point of the spike recovery. A whole new EDTA
solution had to be made just for the spike solution, because I had run out prior to this portion of the lab.
Because the new EDTA solution was not the same as the one prior to the spike, there was some error to
be had. Along with this, I also decided to use a 0.06 M HCl to dissolve the CaCO3, rather than the 0.15
M in the previous lab, so this also added to the error.