EJ Habina
Quantitative Anal. Lab
MW 2:00
Experiment 9: Real World Experiment
Purpose:
The purpose of this experiment was for us as students to design our own
experimental procedure along the guidelines of one we had previously completed this
semester. For my partner and I, we chose to test several sources of water to test the
presence of different hard water ions in each source. We determined this from both
qualitative and well and quantitative methods.
Procedure:
For this procedure my partner and I completed a series of three different methods
to test for the presence of hard water ions in the water samples. The first method was
through direct titration of EDTA, in which a EDTA solution (0.1 M) was used to titrate each
sample of water in order to determine the presence of hard water ions in solution. A
measure of each water sample’s pH was also measured. The last method that was used was
a series of qualitative tests that would show either a positive or negative result regarding
the presence of the particular ion tested for. The procedure for each these tests is outline
below:
1. In a 250 mL beaker, 150 mL of water sample is boiled until approximately 15
mL remain. The remaining water is divided into four test tubes labeled as 1 -8.
The test tubes labeled 1-4 are the tests, where 5-9 are the control samples so
that a positive test is identifiable. The procedure for testing for the presence of
each ion is as follows:
a. 1 – Cl:
i. To #1, 4 drops of dilute nitric acid until acidic (litmus paper)
ii. To #5, add 5 drops of 0.1 M silver nitrate. Repeat with #1 and
notice any precipitate or color changes.
b. 2 – S04:
i. To #6, add 5 drops of 0.1 M barium nitrate
ii. Repeat with #2 and note any changes
c. 3 – Pb:
i. To #7, add 4 drops of 6 M HCl
ii. Repeat with #3 and note any changes
d. 4 – Ca/Mg:
i. To #8, add 0.1 M (NH4)2CO3 drop wise until a precipitate forms.
Do not add more than 15 drops
ii. Repeat with #4, and note any changes
Data:
Mass of EDTA: 0.9309 g
EDTA Titration of Water Samples:
Dr. Peterman's Well Water:
Trial 1
Trial 2
mL EDTA
6.1
6.1
Trial 3
6.1
Average
6.1
Moles of EDTA
0.000181
[Ca] gr/gal
0.424
Off Campus Water:
Trial 1
mL EDTA
4.5
Trial 2
4.4
Trial 3
4.2
Average
4.37
Moles of EDTA
0.00033
[Ca] gr/gal
0.773
Trial 1
8.2
Trial 2
8.3
Trial 3
8.3
Average
8.27
Moles of EDTA
0.000174
[Ca] gr/gal
0.408
On Campus Water:
Trial 1
mL EDTA
4.6
Trial 2
4.6
Trial 3
4.4
Average
4.53
Moles of EDTA
0.000243
[Ca] gr/gal
0.569
Creek Water:
mL EDTA
Dissolved Hard Water Ion Tests:
Positive Test Results:
Sulfate Test
Lead Test
Chloride Test
The solution turns an
extremely opague,
cloudy white and a
precipitate forms
settling on bottom of
test tube.
Calcium/Magnesium Test
The solution turns an
Small, bright white
opaque white color with powder-like precipitate
visible precipate
forms and settles of the
particles suspended in bottom of the test tube;
the solution.
"snow-like".
Not a significant change in
color, but faint white
swirls appear as drops are
added. Grain-like
precipitate slowly forms
on bottom of test tube.
Dr. Peterman's Well Water:
Chloride
Result
+
Sulfate
+
Lead
-
Ca/Mg
+
Off Campus Water:
Chloride
Result
+
Sulfate
+
Lead
-
Ca/Mg
+
Creek Water:
Chloride
+
Sulfate
+
Lead
-
Ca/Mg
+
On Campus Water:
Chloride
Result
+
Sulfate
+
Lead
-
Ca/Mg
+
Result
pH Test:
pH Test
Sample
pH
Dr. Peterman's Well Water
7.7
Off Campus Water
8.02
Creek Water
8.03
On Campus Water
7.77
Calculations:
Concentration of EDTA:
𝑚𝑎𝑠𝑠 𝐸𝐷𝑇𝐴 (𝑔) ×
Ex:
(0.9309 𝑔 𝐸𝐷𝑇𝐴) ×
1 𝑚𝑜𝑙 𝐸𝐷𝑇𝐴
= 𝑀 𝐸𝐷𝑇𝐴
374.24 𝑔
1 𝑚𝑜𝑙 𝐸𝐷𝑇𝐴
1
×
= 0.0399𝑀 𝐸𝐷𝑇𝐴
374.24 𝑔
0.250 𝐿
Moles of EDTA Used:
𝑀 𝐸𝐷𝑇𝐴 × 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝐸𝐷𝑇𝐴 𝑢𝑠𝑒𝑑 (𝐿) = 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝐸𝐷𝑇𝐴 𝑢𝑠𝑒𝑑
Ex:
0.0399 𝑀 𝐸𝐷𝑇𝐴 × 0.00453 𝐿 𝐸𝐷𝑇𝐴 = 1.81 × 10−4 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝐸𝐷𝑇𝐴 𝑢𝑠𝑒𝑑
Moles of Hard Water Ions:
𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝐸𝐷𝑇𝐴 𝑢𝑠𝑒𝑑 = 𝑚𝑜𝑙𝑒𝑠 𝐻𝑎𝑟𝑑 𝑊𝑎𝑡𝑒𝑟 𝑖𝑜𝑛𝑠 = 𝐶𝑎+2 𝑖𝑜𝑛𝑠
Ex:
1.81 × 10−4 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝐸𝐷𝑇𝐴 𝑢𝑠𝑒𝑑 = 1.81 × 10−4 𝑚𝑜𝑙𝑒𝑠 𝐻𝑎𝑟𝑑 𝑊𝑎𝑡𝑒𝑟 𝑖𝑜𝑛𝑠
= 1.81 × 10−4 𝐶𝑎+2 𝑖𝑜𝑛𝑠
Concentration of Hard Water Ions:
𝑚𝑜𝑙𝑒𝑠 𝐻𝑎𝑟𝑑 𝑤𝑎𝑡𝑒𝑟 𝑖𝑜𝑛𝑠 = 𝑚𝑜𝑙𝑒𝑠 𝐶𝑎+2 ×
𝐶𝑎+2 𝑝𝑝𝑚 ×
40.078 𝑔 𝑔𝑟𝑎𝑚𝑠 𝐶𝑎+2 𝑖𝑜𝑛𝑠 1000 𝑚𝑔
=
×
= 𝑝𝑝𝑚
1 𝑚𝑜𝑙
𝐿
1 𝑔𝑟𝑎𝑚
1
𝑔𝑟𝑎𝑖𝑛𝑠
= 𝐶𝑎+2 𝑖𝑛
17.1
𝑔𝑎𝑙
Ex:
1.81 × 10−4 𝑚𝑜𝑙𝑒𝑠 𝐶𝑎+2 ×
40.078 𝑔 0.00725 𝑔 𝐶𝑎+2 𝑖𝑜𝑛𝑠 1000 𝑚𝑔
=
×
= 7.25 𝑝𝑝𝑚
1 𝑚𝑜𝑙
𝐿
1 𝑔𝑟𝑎𝑚
𝐶𝑎+2 𝑝𝑝𝑚 ×
1
𝑔𝑟𝑎𝑖𝑛𝑠 +2
= 0.423
𝐶𝑎
17.1
𝑔𝑎𝑙