American University Inorganic Contaminants Present in Water Samples Lab Report

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pallveechem123
School: Carnegie Mellon University

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General Chemistry 1 Lab Report
Project 1: Inorganic Contaminants present in water samples
1. Introduction
A. Background: Our everyday life is steeped in Chemistry or its applications in one way or the
other. Applications of chemistry impinge upon our daily lives so often that it goes unnoticed. It
indeed defines what we eat, how we transport, what we wear, how we treat illness and what
technology we generally use. Scientists across the world are of the opinion that the chemicals
found in household goods are more toxic and hazardous to human health than ever thought of
before. Since health and wellness can’t be assured only by diet and exercise, but also by limiting
exposure to toxic and hazardous chemicals, it’s a imperative for us to become aware of these
chemicals and take action steps to steer clear of these health hazards to the possible limit. At many
times, we do not know about chemical hazards available in day to day use items. Here, scientists
come to our help; with aid of qualitative tests based on chemical reactions of analyte and based on
the measurements of masses, they identify presence of chemicals hazards and give ways to separate
them out from our day to day use items. For example, food scientists find health hazards chemicals
in fast foods available in markets. By finding health hazard chemicals in fast foods, they keep
people aware of unhealthiness of fast foods. Likewise, analytical chemistry is used in many fields
such as medicine, agriculture, forensic etc.
B. Theory: key scientific concepts / theories used in experiment
Qualitative Analysis: Qualitative analysis of analyte is undertaken to obtain data about analyte.
Main forms of qualitative analysis are as follows:
(i)

Solubility test: Solubility test is used to find out the size and polarity of an unknown
compound of analyte and also to ascertain presence of basic/acidic functional groups1.

(ii)

Conductivity test: Conductivity test is used to determine whether ions of analyte
conducts electricity or not.

(iii)

Ph test: It is used to determine whether a substance is acid or alkaline. If pH value
lower than 7, it is acidic. If greater pH value than 7, it is alkaline.

(iv)

Flame Test: Flame test is conducted in order to determine presence of metal ions in
the analyte.

Quantitative analysis: Quantitative analysis is confirmation analysis. Gravimetric analysis is a
quantitative analysis technique, whereby the amount of an analyte (the ion under analysis) can
be determined through the measurement of mass.
C. Hypothesis Test:
It is hypothesized that analyte is MgSO4. The chemical being odorless and white crystalline solid,
the chemical appears to be MgSO4 on the basis of its texture and color. Moreover, if the qualitative
tests such as pH, solubility, and conductivity and the quantitative test of gravimetric analysis also
approve of the hypothesis, the analyte is MgSO4.
D. Objectives:
(i) The unknown chemical is subjected to qualitative tests, such as pH and solubility tests, in
order to ascertain physical and chemical characteristics of the chemical.
(ii) Gravimetric analysis is performed on the unknown chemical in order to confirm the identity
of the chemical.

II. Methods:
Methods (Qualitative Analysis)1. Solubility test- Through this test we are able to determine the nature of analyte provided
to us through the qualitative tests. Firstly 0.1 grams of the unknown sample (analyte) is
placed in 20 ml of water, ethanol, dilute HCl placed separately in 50 ml beakers. We
needed to be cautious while using the amount of analyte for each test as the amount of
analyte given is very less. After 1 minute we observed the substance behavior and recorded
the results accordingly.
2. Conductivity Test- Now the solutions we obtained after the solubility test were tested for
conductivity by introducing conductivity meter halfway and recording was done for each
solution.
3. pH test- Immediately after the conductivity test pH test was performed via two methods.
The first method involves using a pH meter, and the second method is by using pH strips.
the pH meter was introduced into each of the three solutions separately. Thereafter the pH
strips were introduced into all the three solutions one by one and the values were
determined and recorded on the basis of colour key of pH strip’s box.
4. Flame test- Now a wire loop was cleaned using HCl and deionized water rinse. Thereafter
the wire loop was placed under a flame to ensure its perfect clean state.
Now sample of analyte and was taken and placed under flame, which tends to excite the
electrons of metal ions in the analyte and color of the flame was observed and noted. The
observed color was compared to database of common cation colors and the matching color
metal cation was shortlisted for our further study.

5. Analysis of ions- After we hypothesize the ions after conductivity test and flame test it
was easier to eliminate the compounds present in the list of manual which were not
predicted according to the test results.
Gravimetric Analysis:
After we have analyzed the obtained observations from the earlier tests and duly matching the
data thus acquired to a known compound (mentioned to be available) we confirmed the identity
of the unknown sample.
The procedure for gravimetric analysis was as follows:
We used a test tube to mix sample with water to check the formation of precipitate. In our case
it did not form a precipitate, so we did a second trial with water and sodium carbonate to check
if any reaction happens.
Precipitate was formed and was repeated with increased amount of sample each time.
Firstly, we wrote balanced formula of compounds we are dealing with followed by taking 0.2
grams of analyte (significant amount in order to estimate results with smaller deviation.
We used balanced chemical equation to determine the amount of precipitate by using correct
mole to mole ratio (1:1 in this case).
After we obtained the desired result, we added sufficient quantity of sodium carbonate to water
so that it is just enough to react to yield the theoretical precipitate. To this solution we added
0.25 grams of the sample and waited for few minutes to let the system attain dynamic
equilibrium. Now the solution was filtered with the aid of filter paper. This should be done
very slowly to avoid the precipitate to pass through the filter. The filter paper was passed to
oven to dry the precipitate completely. Now we need to weigh the filter papers before the
precipitate has filtered out on it and the weight of the dried filtrate on filter paper. As we

subtract the weight of filter paper from the weight of the dried precipitate on filter paper, we
can get the weight of precipitate obtained. It is crucial to obtain Error % to ascertain that it
should be less than 5%. We can get error % by dividing absolute value of difference between
experimental and theoretical value by theoretical value and multiplying this value by 100. In
our case we got 3.4%

III-Safety Data Concerning the chemicals being dealt with:
Chemical Name
Sodium Carbonate

Potential Hazards

Safety Equipment needed

Causes serious eye and skin

Safety glasses, lab coat and

irritation

gloves permeable to the
product

Ethanol

Highly flammable liquid and

Safety glasses, gloves and

vapour. May form explosive

protective clothing are must.

mixture with air.

If necessary, face shield
should also be worn.
Emergency eye wash
fountain and shower must be
easily available.

Acetone

Highly flammable liquid and

Safety glasses, gloves and

vapour. Causes serious eye

protective clothing are must.

irritation .May cause

If necessary, face shield

drowsiness and dizziness.

should also be worn.
Emergency eye wash

fountain and shower must be
easily available.

IV ResultsPart 1
After performing solubility, conductivity, flame test and pH test following results were obtained:
Solubility:

Unknown

Water

Ethanol

HCl

Soluble

Insoluble

Soluble

Sample

Conductivity Test
Tap Water
Unknown

27500

Sample

pH Test:
Tap Water

DI water

DI water+

DI water

DI

unknown

+MgSO4

water+CaCl2

8.1

7.3

Sample
pH reading

7.4

7.9

8.7

Flame Test:
Flame colour
Unknown

Small flame,

Sample

Orange and
purple in colour

Part 2:
Calculations:
Dilution Formula, (M 1 V1 ) = (M 2 V2 )

0.250M (V1 ) (0.150M )(525mL)
=
0.250M
0.250M
V1 = 0.15525
= 31.5mL
% wt. solution
0.5 grams of solid
100 mL of water
Weight of Solid in 50 mL of water is calculated
100 mL of water has 0.5 grams of solid
50 ml of water will dissolve 0.25 grams of solid
Preparing solution:
Molarity=mol / L
0.25 M =moles/2L

No of moles =0.5
Theoretical Yield:
MgSO4 + Na2 CO3 → MgCO3 + Na2 SO4
0.25
moles
120.366
= 2.0710 −3 moles

Moles of MgSO 4 in 0.25 grams =

As this reaction is 1:1 molar ratio, and the unknown sample i.e. MgSO4 is a limiting reactant,
we can say that, 2.0710 −3 mole of Mg SO4 will react with 2.0710 −3 mole of Na2CO3 to produce
2.0710 −3 mole of MgCO3.

1 mole of MgCO3 weighs 84.31gm
2.0710 −3 mole of MgCO3 will weigh 84.31  2.0710 −3 grams=0.174grams

1 mole of Na2CO3weighs 105.98 gm
2.0710 −3 mole of Na2CO3 will weigh 105.98  2.0710 −3 grams=0.22 grams

Theoretical Yield of MgCO3 is 0.174 grams
Experimental Yield was 0.168 grams
0.174 − 0.168
100
0.174
= 3.4%

% Error =

V Discussion
Part 1 Discussion:
We conducted qualitative test like solubility, flame and conductivity to ascertain the properties of
the unknown sample. In the solubility test we found out that the unknown sample was soluble in
water and HCl(dilute) and insoluble in ethanol. This test led to our hypothesis that the unknown
compound is soluble in polar solvents while being insoluble in non-polar solvents. Then through

the pH test showed an average value of 8.3 which exhibited it to be slightly alkaline. Thereafter
the conductivity test and flame test showing small orange purple flame and conductivity meter
reading led us to hypothesize that metal ion is Magnesium.
As we needed to determine the composition of the unknown sample we firstly noted the flame
color in flame test. And the orange purple flame matched to that of magnesium. Further solubility
test was matched against scientific database of magnesium salts, and showed that MgSO4 is soluble
in water and soluble in dilute HCl and not soluble in ethanol. pH test result of 8.1 matched with
that of MgSO4 being in range of 5.9-8.2. Lastly conductivity test was most challenging in terms
of matching because the reading of conductivity meter fluctuated. However, the measure value of
conductivity meter matched well with that o...

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Anonymous
Return customer, been using sp for a good two years now.

Anonymous
Thanks as always for the good work!

Anonymous
Excellent job

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