Analytical Chemistry (MODULE 1)
Whether inorganic or organic has to be investigated systematically using wellorganized 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, Quarteringflattening it into a cake-like 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
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.”
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.”
➔
△
(s)
(l)
(g)
Balancing equation terms:
Read as “yields”
Reaction occurs
Heat
Solid
Liquid
Gas
Coefficient
Subscripts
Number beside a letter
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 cake-like or disk shape that is then divided into 4 quadrants. The 2opposite 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+ + ClFe2+ + Cl2 → Fe3+ + 2ClFe2+→ Fe3++ee-→Cl20→ 2Cl-1
-- Fe2+→ Fe2+
-- Cl2-1→ 2Cl-1
(oxidation) (Fe gained 1 electron)
(reduction) (Cl lost 1 electron)
6. What is the molar mass of the following compounds.
a. Epsom Salt, the chemical formula is MgSO 4 . 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
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)
+ 3I2(s) → Al2 I6(s)
a. How many moles of Al2 I6 are produced by the reaction of 4.0 mole of
aluminium?
4.0 mol Al2 X 1 mol Al2 I 6
1
=
2 mol Al2 I 6
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)
a.
+ 4H2O(g)
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
Concentration in Molarity
(in whole numbers)
Acetic Acid, Glacial
17 M
Formic Acid
24 M
Hydrochloric Acid
12 M
Hydrofluoric Acid
29 M
Nitric Acid
16 M
Phosphoric Acid
15 M
Sulfuric Acid
18 M
Ammonium Hydroxide
15 M
Potassium Hydroxide
19 M
Sodium Hydroxide
12 M
Reference: https://www.nestgrp.com/protocols/trng/molarity.shtml
M2 Pre-Task
Copy the table, write the chemical formula on the second column, and compute the
molar mass on the third column. Take a picture of your paper and upload it as your
assignment for this activity.
CHEMICAL NAME
CHEMICAL
FORMULA
Na2SO4
1. sodium sulfate
2. magnesium
H Cl MgO6
chloride hexahydrate 12 2
3. potassium
K3 [Fe(CN)6]
ferricyanide
4. nitric acid
HNO₃
5. silver carbonate Ag2CO3
6. sodium
NaClO
hypochlorite
7. barium iodate
Ba(IO3)2
8. aluminum
C6Al2O12
oxalate
9. silver chromate Ag2CrO4
10. calcium
Ca(OH)₂
hydroxide
COMPUTATION OF MOLAR MASS
COMPUTATION OF
MOLAR MASS
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 =?
Formula: % by mass:
total molar mass of element X 100%
Molar mass of whole compound
Solution: % Cr= 51. 996 X100% =
52%
99.99
% O3= 47.997 X100% = 48%
99.99
(b) Cr2O3
Given:
Total molar mass of element:
Cr2= 51.996 (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
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
Given:
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)
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)
Solution #4
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.