SYLLABUS BASED NOTES FOR THE POST OF JUNIOR LABORATORY ASSISTANT IN MEDICAL EDUCATION PART 3 CHEMISTRY (Module 1)

SYLLABUS BASED NOTES FOR THE POST OF JUNIOR LABORATORY ASSISTANT IN MEDICAL EDUCATION PART 3 CHEMISTRY (Module 1)

 PART III : CHEMISTRY (15 Marks) 

Module I : Physical Chemistry (5 Marks)

✅ Some basic concepts of chemistry-mole concept calculation, definition of molarity, molarity calculations.
 
Structure of atom-Different atom model –Rutherford, Neils Bohr, concepts of orbitals, quantum number, shape of s,p,and d orbitals, rules for filling electrons in orbitals

Equilibrium- concept of PH
Electrochemistry-Different types of electrochemical cells(Galvanic, also called voltaic and electrolytic)

Surface chemistry – Colloids and emulsions- type of colloids with examples – colloids around us
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SYLLABUS BASED NOTES  FOR THE POST OF JUNIOR LABORATORY ASSISTANT IN MEDICAL EDUCATION  PART 3 CHEMISTRY  (Module 1)



1. SOME BASIC CONCEPTS OF CHEMISTRY 

Chemistry is the branch of Science that deals with the properties, structure and composition of matter. 

There are a large number of branches for Chemistry. Some of them are:
1. Inorganic Chemistry 
2. Organic Chemistry 
3. Physical Chemistry 
4. Analytical Chemistry 
5. Polymer Chemistry 
6. Biochemistry 
7. Medicinal Chemistry 
8. Industrial Chemistry 
9. Hydrochemistry 
10. Electrochemistry 
11. Green Chemistry etc. 

Matter: 
Matter is anything that occupies space, has a definite mass and can be perceived by any of our sense organs. 

Based on the physical state we can divide matter into different categories
1. Solid state 
2. Liquid state 
3. Gaseous state 
4. Plasma state 
5. Bose-Einstein condensate 
6. Fermionic condensate 

Classification of matter Based on the chemical composition of matter can be divided into two categories - pure substances and mixtures

Pure substances contain only one type of particles. 
E.g. sodium (Na), Potassium (K), Hydrogen (H), Oxygen (0), Helium (He), Carbon dioxide (CO2), ware (H₂O), ammonia (NH3), cane sugar (C2H22O1) etc. 

These are further divided into two-
elements and compounds. 

Elements are pure substances which contain only one type of particles. These particles may be atoms or molecules.
The term element was first introduced by Robert Boyle, the father of ancient Chemistry. 
Now there are about 118 elements. 
Some elements exist as monoatomic and some others are polyatomic.
 E.g.• Hydrogen, Nitrogen, Oxygen (diatomic), 
       • Sodium, Potassium, Lithium, Calcium (monoatomic), 
       • Phosphorus, Sulphur (polyatomic) etc. 

Compounds are pure substances which contain more than one type of atoms. 
E.g. CO₂, H₂O, NH, H₂SO, etc. 

Mixtures contain more than one type of particles.
 E.g. all types of solutions, gold ornaments, sea water, muddy water, air etc

There are two types of mixtures-homogeneous and heterogeneous mixtures

Mixtures having uniform composition throughout are called homogeneous mixtures.
E.g. all type of solutions, air etc.

 Mixtures having different compositions at different parts are called heterogeneous mixtures.
 E.g. sea water, soil etc

Mass and Weight 

Mass is the amount of matter present in a body. 
It is a cogitant quantity.
 Its SI unit is kilogram (kg)

Weight is the gravitational force acting on a body. 
It is a variable quantity. i.e. it changes with place.
 Its SI unit is newton (N).

 Volume (V) It is the space occupied by a body. 
Its SI unit is m3.
 Other units are cm3, mL, L etc. 

1 m³ = 10 cm³ 
1cm² = 1 mL 1 
L=103 cm³ (mL) 
1 dm³ = 10³ cm³ 

Density (d) It is the amount of mass per unit volume. i.e. density = mass/volume.
 Its SI unit is kg/m³
But it is commonly expressed in g/cm³

Temperature (T) It is the degree of hotness or coldness of a body. 
It is commonly expressed in degree Celsius (°C). Other units are degree Fahrenheit (°F), Kelvin (K) etc. 
its SI unit is Kelvin (K)

Degree Celsius and degree Fahrenheit are related as: 
°F = 9/5(°C) +32 

Degree celsius and Kelvin are related as:
 K = °C +273.15 

Precision and Accuracy 
Precision refers to the closeness of various measurements for the same quantity. But, 

accuracy is the agreement of particular value to the true value of the result. Significant Figures

LAWS OF CHEMICAL COMBINATIONS 
The combination of elements to form compounds is governed by the following five basic laws: 

1. Law of Conservation of Mass (Law of indestructibility of matter): 
This law was proposed by Antoine Lavoisier.
 It states that matter can neither be created nor destroyed. 

We can only convert one form of matter into another form. Or, in a chemical reaction, the total mass of reactants is equal to the total mass of products. 

Chemical equations are balanced according to this law. Illustration 
Consider the reaction 
2H₂+O₂ 2H₂O 
Here 4 g of H₂ combines with 32 g of O₂ to form 36 g of water. 
Total mass of reactants = 4 + 32 = 36g 
Total mass of products = 36 g

2. Law of Definite Proportions (Law of definite composition): 

This law was proposed by Joseph Proust.
 It states that a given compound always contains exactly the same proportion of elements by weight. Or, the same compound always contains the same elements combined in a fixed ratio by mass. 

Illustration: Carbon dioxide can be formed in the atmosphere by various methods like respiration, burning of fuels, reaction of metal carbonates and bicarbonates with acid etc. 

All these samples of CO₂ contain only two elements Carbon and Oxygen combined in a mass ratio 3:8

3. Law of Multiple Proportions: 

This law was proposed by John Dalton
It states that if two elements can combine to form more than one compound, the different masses of one of the elements that combine with a fixed mass of the other element, are in small whole number ratio. 

Illustration: Hydrogen combines with oxygen to form two compounds - water and hydrogen peroxide. 

Hydrogen + Oxygen → Water 
2g                 16g             18g 

Hydrogen + Oxygen → Hydrogen Peroxide 
34g               28              32g 

Here, the masses of oxygen (i.e. 16 g and 32 g) 
which combine with a fixed mass of hydrogen (2g) bear a simple ratio, 
i.e. 16:32 or 1: 2

4. Gay Lussac's Law of Gaseous Volumes: 

This law was proposed by Gay Lussac
It states that when gases combine to form gaseous products, their volumes are in simple whole number ratio at constant temperature and pressure. 

Illustration: H₂ combines with O₂ to form water vapour according to the equation 
2H2(g) + O2(g) → 2H₂O(g). 

If 100 mL of hydrogen combine with 50 mL of oxygen, we get 100 ml of water vapour. 

Thus, the volumes of hydrogen and oxygen which combine together (i.e. 100 mL and 50 mL) bear a simple ratio of 2:1. 5.

 Avogadro's Law: This law was proposed by Amedeo Avogadro It states that equal volumes of all gases at the same temperature and pressure should contain equal number of moles or molecules

DALTON'S ATOMIC THEORY 
The term atom was first used by John Dalton from the Greek word a-tomio (means indivisible).
 He proposed the first atomic theory. 
The important postulates of this theory are: 

1. Matter is made up of minute and indivisible carticles called atoms. 
2. Atoms can neither be created nor be destroyed. 
3. Atoms of same element are identical in their properties and mass. While atoms of different elements have different properties and mass 
4. Atoms combined to form compound atoms called molecules. 
5. When atoms combine, they do so in a fixed ratio by mass. 

Dalton's theory could explain the laws of chemical combination. 

Atoms and Molecules 

Atom is the smallest particle of an element. 
Molecules are the smallest particle of a substance.es called atoms. A molecule has all the properties of that substance. 
Types of molecules 
Based on the type of atoms, there are two types of molecules - homonuclear molecule and heteronuclear molecule

A molecule containing only one type of atom is called homonuclear molecule. 
e.g. H₂, O2, N2, O, (ozone) etc 

Heteronuclear molecules contain different types of atoms.
 E.g. CO₂, H₂O, CH12O6, NH, etc. 

Based on the no. of atoms there are three types of molecules - monoatomic, diatomic and polyatomic molecules.

 Monoatomic molecules contain only one atom. 
E.g. all metals, noble gases like He, Ne, Ar etc. 

Diatomic molecules contain 2 atoms.
 E.g. H₂, O2, N2, halogens (F2, Cl, Br, and I₂) has all the properties of that substance. 
Types of molecules Based on the type of atoms, there are two types of molecules - 
homonuclear molecule and heteronuclear molecule. 

A molecule containing only one type of atom is called homonuclear molecule. 
e.g. H₂, O2, N2, O, (ozone) etc 

Heteronuclear molecules contain different types of atoms.
 E.g. CO₂, H₂O, CH12O6, NH, etc.

 Based on the no. of atoms there are three types of molecules - monoatomic, diatomic and polyatomic molecules

Monoatomic molecules contain only one atom. 
E.g. all metals, noble gases like He, Ne, Ar etc. 

Diatomic molecules contain 2 atoms. 
E.g. H₂, O2, N2, halogens (F2, Cl, Br, and I₂)

Polyatomic molecules contain more than two atoms. E.g. ozone (O), Phosphorus (P), Sulphur (S) etc. 

Atomic mass 
Atomic mass of an element is a number that expresses how many times the mass of an atom of the element is greater than 1/12th the mass of a C22 atom
For e.g. atomic mass of Nitrogen is 14, which means that mass of one N atom is 14 times greater than 1/12th the mass of a C¹² atom. 

Atomic mass unit (amu): 
1/12th the mass of a C22 atom is called atomic mass unit (amu). 
i.e. 1 amu = 1/12 x mass of a C¹² atom 
= 1.66 x 1024 g
 = 1.66 x 1027 kg 
Today, 'amu' has been replaced by 'u' which is known as unified mass

Average atomic mass: 
All most all the elements have isotopes. So we can calculate an average atomic mass of an element by considering the atomic mass of the isotopes and their relative abundance. 
For e.g. chlorine has two isotopes C135 and C137 in the ratio 3:1. 
So the average atomic mass 
Cl =(3x35 + 1x37)/4 
=35.5 

Molecular mass: 
Molecular mass is the sum of atomic masses of the elements present in a molecule. 
It is obtained by multiplying the atomic mass of each element by the number of its atoms and adding them together. 
For e.g. molecular mass of H₂SO, is calculated as:
 2 x 1 +32 +4 x 16 = 98 u. 

Formula mass: 
In the case of ionic compounds (like NaCl), there is no discrete (separate) molecules. Here the positive ions and the negative ions are arranged in a three-dimensional structure. 
So we can calculate only formula mass by taking molecular formula of the compound. 

Mole concept 
Mole is the unit of amount of substance. It is defined as the amount of substance that contains as many particles as there are atoms in exactly 12 g C2 isotope.
 1 mole of any substance contains 6.022 x 10" atoms. This number is known as Avogadro number or Avogadro constant (Nor) 

1 mol of hydrogen atoms = 6.022×1023 atoms 
1 mol of water molecules = 6.022×1023 water molecules 
1 mol of sodium chloride = 6.022 x 1023 formula units of sodium chloride

Molar mass: The mass of one mole of a substance in grams called its molar mass (gram molecular mass). The molar mass in grams is numerically equal to molecular mass 
Molar mass of oxygen =32g

Molar mass of hydrogen=2g


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