Analytical Chemistry (MODULE 1)
Whether inorganic or organic has to
be investigated systematically using
well-organized methods where
meticulous observations are done so
that logical conclusion is made
accurately.
Uses instruments to separate, identify
and quantify matter
precise measurements are usually
needed to determine its exact
composition.
Aims to determine what elements,
ions, functional groups, or compounds
are present in a given sample.
Analytical chemists in industry:
Lawyers, Other chemists, Colleges
universities, Health and safety,
Production plants, Contract labs,
Management, Professional
organizations, Statisticians,
Government agencies, Engineers,
Suppliers, Sales and marketing, Life
scientists, Technical reps in field,
Peers, supervisors, Forensic chemists.
(In 1997, the quest for information
from the planet Mars by the
Pathfinder spacecraft used qualitative
analysis to determine what
compounds or elements were in the
rock samples.)
Quantitative analysis: know how
much of the compound, ions, or
elements confirmed present by
qualitative analysis is actually present.
Determines numerical amount or
concentration
hundred(percentage), parts per million
(ppm) or part per billion(ppb)
(uses mass or volume)
Qualitative analysis: Identifies
analytes (substances)
Separation-isolates analytes
(substances)
i.e. precipitation, extraction,
distillation
Identification of substance: may be
based on color, odor, melting point,
boiling point, and
radioactivity/reactivity.
Sampling techniques
Analytical chemists utilize coning and
quartering to decrease the sample size
of a powder without producing
systematic bias.
Coning involves putting the sample
into a conical shape and then,
Quartering- flattening it into a cakelike or disk shape that is then divided
into 4 quadrants. The 2-opposite
quadrant are combined forming
another cone and then quartered
again. This process will continue until
the sample will reduce small enough
to fit for laboratory sample. Then the
sample will be dissolved in water that
we can call Aliquot- the exact divisor
or factor of a quantity.
Basic chemistry principles
Law of definite composition
No matter what the source, a
particular compound is composed of
the same elements in the same parts
(fractions) by mass.
“every chemical compound contains
fixed and constant proportions.”
Law of multiple proportion
If element A and B react to form two
compounds, the different masses of B
that combine with a fixed mass of A
can be expressed as a ratio of small
whole numbers.
“When two elements combine to
generate more than one compound,
the weights of one element mix with a
fixed weight of the other in a tiny
whole number ratio.”
Chemical reactions- conversion of
natural substances into new
compounds with different and
sometimes superior
properties.
✓ breaking bond in the reactants
(starting materials)
✓ Forming new bonds in the
product
✓ Involves to metabolism of food,
as well.
Law of mass conservation
The total mass of substances does not
change during a chemical reaction
“atoms cannot be created or
destroyed.”
Balancing equation terms:
➔
Read as “yields”
Reaction occurs
Heat
△
(s)
Solid
(l)
Liquid
(g)
Gas
Coefficient
Number beside a letter
Subscripts
Set slightly below or above the normal
line
Reactant
Substance that takes part in and undergoes
change during a reaction.
Product
Substance that is formed as the result of a
chemical reaction.
Chemical equation- chemist’s
shorthand descriptions
Steps in balancing chemical
equation
Step1 Write the equation with the
correct formulas.
Step2 Balance the equation with
coefficients one element at a time.
Step3 Check to make sure that the
smallest set of whole numbers is used.
Redox reaction
- Addition of oxygen
- Increase in valence/oxidation
number
- Loss of electron or hydrogen
- Substances oxidized
- Reducing agent
VILEORA -Valence of an element
Increases that means it Lost Electron,
it was Oxidized and its compound
acts as the Reducing Agent.
Reduction reaction
- Addition of hydrogen
- Decrease in valence/ oxidation
number
- Gain of electron or hydrogen
- Substance reduced
- Oxidizing agent
VDGEROA- Valence of an element
Decreases that means it Gained
Electrons, it was Reduced and its
compound is the Oxidizing Agent.
Module 1 Activities:
M1 Pre-Task
Take a look at the nutrition facts on
your favorite snack. Note also the
content of each multi-vitamin tablet.
What appears on the label is from the
tedious analysis of analytical chemists.
Have pictures of these (one each) and
upload them in the reply box.
M1 Activity 1
After studying the lesson and
watching the videos, answer the
following questions in the reply box.
The answer must not exceed 5
sentences per question.
1. What problems of society can
analytical chemists help in
finding solutions? How do they
do it?
In forensic science, investigators are
able to detect illegal compounds from
suspected drug users using analytical
chemistry. In breath biopsy, chemical
analysts recognize valuable
information about a disease like
asthma, or any infectious disease.
Chemistry is truly majestic in its own
right. Another advantage of chemistry
is that it helps with our problem of
plastic pollution and environmental
monitoring. Analytical chemistry is
also used in food production, which
we may not be aware of, but the
nutritional facts of our food are from
the analysis of an analytical chemist.
2. Discuss the quartering method
of sampling.
First, a sample must shape into
conical/ cone form and then,
Quartering- flattening it into a cakelike or disk shape that is then divided
into 4 quadrants. The 2-opposite
quadrant are combined forming
another cone and then quartered
again. This process will continue until
the sample will reduce small enough
to fit for laboratory sample. Then the
sample will be dissolved in water that
we can call Aliquot- the exact divisor
or factor of a quantity. This is utilized
by the chemists in order to decrease a
sample size that can fit in the
laboratory.
M1 Activity 2
After studying the lesson and the
PowerPoint presentations, please
answer the following questions. Use
one whole sheet intermediate pad
paper folded lengthwise. Write legibly
and no erasures. For numbers 6-8,
show your solution, encircle final
answer and final answer must have
correct number of significant figures.
1. Write a complete balanced
chemical
equation
for
the
decomposition of solid potassium
chlorate upon heating.
2KClO3 (s) → 2KCl(s)
+ 3O2
2. Balance and translate the given
chemical equation to a word
equation.
BaCl2(aq) + Na2SO4(aq) →
BaSO4(s) + 2NaCl(aq)
Barium chloride reacts with sodium
sulphate to produce insoluble
barium sulphate (precipitate) and
sodium chloride solution
3. Three moles of sulphuric acid react
with two moles of aluminium metal
to give one mole of aluminium
sulphate and three moles of
hydrogen gas. Write the balanced
chemical equation corresponding
to this reaction.
3(H2SO4) (aq) + 2Al → Al2
(SO4)3(aq) +3H2 (g)
4. Balance the given equation using
the valence change method.
Identify the reducing agent and the
oxidizing agent.
H2S + H2O2 → S + H2O
H2 -1S-2 (g) + H2 -2O2-1 (aq) → S0 (s)
+ 2 H2 -1O-2 (l)
H2S is a reducing agent, H2O2 is an
oxidizing agent.
S-II - 2 e- → S0 (oxidation)
2 O-I + 2 e- → 2 O-II (reduction)
5. Balance the given equation using
the half-reaction method. Identify
the ion or element that gained
electron and indicate the number of
electrons gained. Identify the ion or
element that lost electron and
indicate the number of electrons
lost.
Fe2+ + Cl2 → Fe3+ + C
lFe2+ + Cl2 → Fe3+ + 2Cl-
H= 1.00784
P= 30.973762
O= 15.999
(14.0067+ 1.00784*4)3+ 30.973762+
(15.999* 4)
Molar mass of (NH4)3PO4 =
149.05 g/mol
7. Aluminium reacts with iodine
according to the following equation:
2Al(s)
Al2 I6(s)
a. How many moles of
Al2 I6 are produced by the
reaction of 4.0 mole of
aluminium?
Fe2+→ Fe3++e-- Fe2+→ Fe2+
(oxidation) (Fe gained 1 electron)
e-→Cl20→ 2Cl-1
-- Cl2-1→ 2Cl-1
(reduction) (Cl lost 1 electron)
6. What is the molar mass of the
following compounds.
a. Epsom Salt, the chemical
formula is MgSO4 . 7H2O
Mg=24.305
S=32.065
O=15.9994
H=1.00794
24.305 + 32.065 + 15.9994*4 +
7*(1.00794*2 + 15.9994)
Molar mass of
MgSO4.7H2O =
246.47g/mol
b. Ammonium phosphate
(NH4)3PO4
N= 14.0067
+ 3I2(s) →
4.0 mol Al2 X 1 mol Al2 I 6
mol Al2 I 6
1
=
2
2 mol Al2
b. How many moles of I2 are
required to react exactly with
0.429 mole of aluminium?
0.429 A2 X 3 mol I2
1
= 0.64 mol I2
2Al2
8. Methanol (CH4O), which is used as
a fuel in high –performance racing
cars, burns in the presence of O2 to
form CO2 and H2
2CH4O(l) + 3O2(g)
→ 2CO2(g) + 4H2O(g)
a. What is the theoretical yield of
CO2 from 48.0 grams of methanol?
48.0 g CH4O X 1 mol CH4O
=1.50 mol CH4O X 2 mol
CH4O = 1.50 mol CO2 X
44.0 g CO2
1
32.0 g CH4O
2 mol CH4O
2 mol CH4O
= 66.0 g CO2 Theoretical
yield
b. What is the percent yield of
CO2 if 48.0 grams of carbon dioxide
are formed?
Percent yield = 48.0 g CO2
X
100% = 72.7%
66.0 g CO2
Research and type the molarity of the
following concentrated acids, bases,
and salts using the table below.
Name of Acids/Bases
Acetic Acid, Glacial
Formic Acid
Hydrochloric Acid
Hydrofluoric Acid
Nitric Acid
Phosphoric Acid
Sulfuric Acid
Ammonium Hydroxide
Potassium Hydroxide
Sodium Hydroxide
Reference:
https://www.nestgrp.com/protocols/tr
ng/molarity.shtml
M2 Activity 1
Solve the following problems. Use
intermediate pad paper. Write legibly
and no erasures. Follow the given
format below. Final answers must
contain the correct number of
significant figures. Upload your
assignment as a picture.
1. Calculate the percent by mass of
chromium in each of the following
oxides:
a. CrO3
Problem #
1.a. Given:
Total molar mass of element:
Cr= 51.996
O3= 15.999 (3)= 47.997
Molar mass of CrO3 = 99.99
Req’d= % mass of CrO3 =?
in Molarity
Formula: %Concentration
by mass:
total molar mass of element X 100%
(in whole numbers)
Molar mass of whole compound
17 M
Solution: % Cr= 51. 996 X100% =
24 M
52%
12 M
99.99
%M
O3= 47.997 X100% = 48%
29
99.99
16 M
15 M
(b) Cr2O3
Given: 18 M
15 M
Total molar
mass of element:
Cr2= 51.996
19 M(2) = 103.992
O3= 15.999 (3) = 47.997
Molar mass of Cr 2O3 = 99.99
Req’d= % mass of Cr 2O 3 =?
Formula: % by mass:
total molar mass of element X 100%
Molar mass of whole compound
Solution: % Cr2= 103.992 X100% =
68.42%
151.99
% O3= 47.997 X100% =
31.58%
151.99
2. A commercial mouthwash contains
4.3 g of ethanol and 0.021g
antiseptic in each 30.-mL portion.
Calculate
the
w/v
percent
concentration of each component.
Given:
Solutes: 4.3g of ethanol
0.021 g of antiseptic
Solution: 30. mL
Req’d= w/v of ethanol= ?
w/v of antiseptic =?
Formula:
(w/v)= mass of solute (g) X100%
Vol. of solution (mL)
Solution: (w/v)= 4.3 (g)
X100%
=14% (ethanol)
0.021 (mL)
(w/v)= 0.021 (g) X100%
=0.070% (antiseptic)
30.(mL)
3. How many mL of ethanol are
contained in a 30.-mL portion of
Solution #4
mouthwash that has 8.0%(v/v) of
ethanol?
Given:
Solute: ?
Solution: 30. mL
(v/v): 8.0%
Req’d= ml of ethanol= ?
Formula:
(v/v)= mass of solute (g) X100%
Vol. of solution (mL)
Solution: 8.0%= ? mLX100%
30. mL
: 8.0% = ? mL
X100%
100mL 30. mL
=0.08 mL X 30. mL
=2.4 mL ethanol
4. A cough medicine contains 0.20%
(w/v) dextromethorphan, a cough
suppressant , and 2.0% (w/v)
guaifenesin, an expectorant. How
many mg of each drug would you
obtain from 3.0 tsp of cough syrup?
(1 tsp = 5 ml)
Given:
0.20% (w/v) dextromethorphan
2.0% (w/v) guaifenisin
3.0 tsp = 5 mL cough syrup
Req’d= ml of ethanol= ?
Formula:
(v/v)= mass of solute (g) X100%
Vol. of solution (mL)
5 mL cough syrup X 0.20% g dextromethorphan X
dextromethorphan
100 mL cough syrup
1000 mg = 25.0 mg
1g
5 mL cough syrup X 2.0 g guaifenesin X 1000 mg = 10 mg guaifenesin
100 mL cough syrup
1g
M2 Activity 3
A. Write a balanced chemical equation, total ionic equation and net ionic equation
for the given
pairs of salt solutions when they are mixed.
1. Pb(NO3)2 + K2SO4 →
Balanced chemical equation:
Pb(NO3)2 (aq) + K2SO4 (aq) → PbSO4 (s) + 2 KNO3 (aq)
Ionic equation:
Pb 2++ 2NO3 - (aq) + 2K +SO4 2- (aq) → PbSO4 (s) + 2 K + + 2NO3- (aq)
Net ionic equation:
Pb 2+ (aq) +SO4 2- (aq) → PbSO4 (s)
2. FeCl3 + NaOH
→
1. Balanced chemical equation:
FeCl3 (aq) + 3NaOH(aq) → Fe(OH)3(s) + 3NaCl(aq)
2. Ionic equation:
Fe 3+ 3Cl- (aq) + 3Na+ 3OH -(aq) → Fe (OH)3(s) + 3Na + 3Cl -(aq)
3. Net ionic equation:
Fe 3+(aq) + 3OH -(aq) → Fe (OH)3(s)
B. For the precipitate formed in question A, write its formula, chemical name and
classification.
Precipitate Formula - chemical name - classification
1. PbSO4 - lead(II) sulfate- sulfuric acid lead salt or anglesite
2. Fe (OH)3 - Iron(III) oxide-hydroxide- transition element molecular entity and
a metallic base.
Apparatus/
Equipment
How You Used It Before
Correct Technique in Using It
Crucible
I completely fill it.
Fill the crucible only halfway or
two-thirds full of sample
chemicals; do not fill it all the
way to the top.
Evaporating
dish
One time, I forgot to
Should record the mass of the dish
record the mass of the dish
before measuring solution
Sample vial
No labeling of samples
Samples should always be labeled
Graduated
cylinder
I use it to hold water
It is used for measuring a solution
or any liquid sample.
M1 Activity 3
1. Discuss the correct laboratory technique in using the centrifuge for
qualitative analysis. Give two tips on its proper use.
First, calibration of the centrifuge before testing a sample has to be prioritized.
Along with the test tube samples, another tube filled with water at approximately
the same level as your sample test will be put. This water-filled tube should be put
exactly across from your sample in the centrifuge. Hands should not be used to
slow down the centrifuge head. Allow the centrifuge head to come to rest on its
own instead.
2. Explain how calcium ions are confirmed present in a solid salt by using
flame test.
The flame test is used to visually identify an unknown metal or metalloid ion based
on the salt's unique color. A few drops of dilute sodium hydroxide solution react
with calcium ions to generate a white precipitate is the confirmation test.
3.Discuss a method to confirm the presence of a) phenol and b) ketone in a test
compound.
For the presence of phenol, make a solution of the organic compounds supplied in
water, dropwise add the ferric chloride neutral solution then the color shift. The
presence of phenol is indicated by the presence of red, blue, green, or purple
coloration. While the presence of ketone is confirmed if there is the emergence of a
red color. In a clean test tube, dissolve sodium nitroprusside in distilled water. 1ml
of the organic substance to be examined is added then shake thoroughly before
adding the sodium hydroxide solution dropwise.
4. How are proteins confirmed present in a sample? Explain the laboratory
process.
The Biuret test for proteins is used to determine the presence of protein. The
Biurette reagent, which is composed of sodium hydroxide and copper (II) sulphate,
aids in the detection of protein in a sample. For its procedure, add 2ml of the
sodium hydroxide solution then, add 5 to 6 drops of copper sulfate solution to this.
The presence of proteins is indicated by the appearance of a bluish violet color.