Fundamentals of Chemistry Notes

Fundamentals of Chemistry

Fundamentals of Chemistry Notes

What exactly is science?

Science is the systematic body of knowledge gathered via observations and experimentation.

Explanation

Our five senses acquire information about the material cosmos, which forms knowledge.

When the authenticity and veracity of facts are proved through experiments, however, this is referred to as science.

Example:

Water freezes at 0 degrees Celsius and boils at 1000 degrees Celsius.
When hydrogen and oxygen are joined chemically in a defined ratio, water is produced.

What is chemistry?

Chemistry is the discipline of science concerned with the study of matter, its composition, structure, properties, and reactions.

Chemistry is essential to many facets of existence.

applications of chemistry
applications of chemistry

Check out -> Fundamentals of chemistry mcqs

Origin of Chemistry

The origin of the term chemistry is the word KEEM. The same name was given to ancient Egypt. As time progressed, the science of chemistry spread from one generation to the next and eventually reached Arabia. There, the name KEEM was changed to AL KIMIYA.
The primary objective of chemistry is to understand the properties and transformations of matter. Chemistry is essential to our daily lives.

Simply stated, chemistry is the study of matter.

Branches of Chemistry with Examples

Following are the different branches of chemistry

Organic chemistry

“Organic chemistry is the discipline of science that studies molecules containing carbon.”

The majority of items we encounter on a daily basis are organic in origin. e.g.

Organic chemistry uses

• The majority of the food we eat is organic in nature.
• We wear organic clothing, such as cotton, silk, wool, etc.
• Coal, natural gas, and petroleum products are organic.
• Fuels that power our automobiles and businesses, such as gasoline, diesel, compressed natural gas (CNG), and coal gas
• Both allopathy and homoeopathy utilise chemical molecules. such as Penicillin and streptomycin

Other organic compound applications
• Insecticides such as DDT • Hormones & Steroids • Vitamins & Enzymes • Pigments & Dyes • Paper & Inks • Perfumes & Flavors • Plastic & Rubber • Explosives • Soap & Detergents • Herbicides such as Treflan • Photographic films & develops etc.

Carbon compounds with few exceptions

The following are exceptions:

  1. Carbon monoxide (CO)
  2. Carbon dioxide (CO2)
  3. Carbon disulphide (CS2)
  4. Carbonates (CO32-)
  5. Bicarbonates (HCO3-)
  6. Cyanides (CN-)
  7. Cyanates (CNO -)
  8. Metal Carbides (C4-) etc.

Inorganic Chemistry

“Inorganic science is the discipline of chemistry that studies all elements and their compounds with the exception of organic compounds.”

Illustrations of inorganic compounds

ionorganic chemistry

Other applications of inorganic compounds include glass, washing soda (Na2CO3.10H2O), ceramics, etc.

Analytical Chemistry

Analytical chemistry is the discipline of chemistry that focuses on the procedures and tools used to determine the composition of matter.

Analytical chemistry

To check

Analytical chemistry

Biochemistry

Biochemistry is the branch of chemistry concerned with the physical and chemical processes that occur in living organisms.

Biochemistry

For Example:

In the presence of chlorophyll and sunlight, photosynthesis produces glucose and oxygen from CO2 and H2O. Since photosynthesis is a chemical process that plants undergo.

Biochemistry uses

Biochemistry is also the study of chemical reactions that occur within the human body.

Biochemistry uses

Industrial Chemistry

Industrial chemistry is the subfield of chemistry that focuses on the methodologies and application of technology in the mass production of valuable compounds.

Industrial Chemistry

Massive manufacturing of any substance

The technique developed by Haber turns vast volumes of hydrogen and nitrogen into ammonia.

ammonia manufacturing

Nuclear chemistry

“Nuclear chemistry is the branch of chemistry that deals with the changes that occur in atomic nuclei.”

Nuclear chemistry

Example:

The study of the consequences of radioactive radiation or nuclear changes.
For instance, when alpha particles hit a nitrogen-14 atom and a proton is emitted, the process is represented as follows:

Nuclear chemistry

The processes of nuclear fission and fusion can be explained by nuclear chemistry

Environmental Chemistry

Environmental chemistry is the branch of chemistry concerned with chemicals and harmful compounds that contaminate the environment and their negative impact on humans.

Environmental Chemistry

Examples 1

Plantation aids in the mitigation of the greenhouse impact.

Environmental Chemistry

Examples 2

Compounds containing chlorofluorocarbons are responsible for the depletion of the ozone layer.

Since ozone layer depletion is an environmental issue.

Examples 3

Environmental Chemistry

Physical Chemistry

Physical chemistry is the discipline of chemistry concerned with the principles and theories necessary to comprehend the structure and transformations of matter.

Physical Chemistry

OR

Physical Chemistry is the study of the concepts and principles that help us to grasp the structure and transformations of matter.

EXAMPLE

When heated, water evaporates and transforms into vapours. This phenomenon is explained by means of physical chemistry

Differentiate between the Branches of Chemistry

Vinegar contains 5% acetic acid. Acetic acid (CH3COOH) is an odourless, colourless liquid with a vinegar-like odour. It is used as a flavouring agent. Various forms of research on this substance can help you distinguish between different disciplines of chemistry.

Branches of Chemistry

Physical chemistry explains its transformation into a gaseous or solid state and applies laws and theories to comprehend its structure.

Branches of Chemistry

Since it is a carbon-containing substance, organic chemistry is the study of its chemical characteristics and technique of manufacture.

Branches of Chemistry

Examine its component parts. C, H, and O constitute inorganic chemistry.

Branches of Chemistry

Biochemistry is the study of the chemical interactions that acetic acid undergoes in the human body.

Branches of Chemistry
Branches of Chemistry
Branches of Chemistry
Branches of Chemistry

Dalton’s atomic theory

In 1803, English chemist John Dalton presented a theory on the nature and existence of matter

Basic postulates of dalton’s atomic theory

  • Everything is composed of tiny indestructible particles called atoms
  • Atoms of the same element have the same properties
  • During chemical reactions, atoms combine in a simple ratio to form compounds
  • Atoms can neither be created nor destroyed.

Basic Chemistry Definitions

What is meant by matter?

“Matter is everything that has mass and takes space.”

 define matter

What is a substance?

Substance refers to the type of matter that has a particular composition and specific characteristics.

Or

A substance is any type of matter that possesses a unique set of characteristics different from those of another type of matter.

define substance
what is substance

A substance may be in solid, liquid or gaseous form.

Examples of Substances

  • Water
  • Carbon dioxide
  • Oxygen, Hydrogen, Common salt etc.

Types of Substances

1. Pure Substance

2. Impure Substance

types of  substance

What is an element?

define element

An element is a pure substance that cannot be broken down into smaller substances. Each element’s atoms include the same atoms, which have identical structural and chemical properties.
There are 118 naturally occurring elements, of which 92 are found in nature and the remainder are created in laboratories.

An element is represented by a symbol

elements symbols

Atoms are the smallest particles of elements.

smallest particle of an element

Elements have uniform composition throughout.

Element Examples

Sodium ( Na )

Magnesium ( Mg )

Oxygen  ( O )

Argon   ( Ar )

Some elements are represented by their Latin names e.g

  1. Copper    Cuprum        Cu
  2. Silver        Argentum     Ag
  3. Tin            Stannum       Sn

An element may be in solid, liquid or gas form.

An element may be in solid, liquid or gas form.
solid, liquid or gas form of elements

Compound

A compound is a pure substance composed of two or more elements kept together in a constant proportion by chemical bonds.

what is compound

Compounds are formed by the chemical combination of elements whose properties are entirely distinct from those of their parent elements. As a compound is a pure substance, its constituents cannot be separated through physical means.
The most essential property of a compound is its constant mass ratio. Hydrogen Peroxide [H2O2] is an example of a compound. Which is applied to the skin as an antiseptic to prevent infection from minor cuts? In hydrogen peroxide, the ratio of hydrogen to oxygen is always 2:2. Changing this ratio will yield an entirely different compound.

Compounds Characteristics

  • The properties of compounds are different from the properties of the elements from which they are formed.
  • A compound may be ionic or covalent
  • Compounds have uniform composition throughout
  • Millions of compounds exist in a universe
  • Compounds are represented by chemical formulas

Additional Information

Note!!

Ionic bond

The complete transfer of an electron from one atom(metal)  to another atom(non-metal)is called an ionic bond.

ionic bond
nacl ionic bond

Covalent bond

A covalent bond is formed by the mutual sharing of electrons between the atoms.

covalent bond formation
covalent bond formation
Representation of compounds

The constituents of a compound are represented through a chemical formula. The formula shows the elements which chemically combined to form that particular compound.

Compound Examples

Hydrogen Peroxide   H2O2

Water     H2O

Methane [Natural Gas]     CH4

What is a mixture?

A mixture contains two or more pure substances that retain their individual chemical properties.

mixture formation
mixture formation

A mixture is an impure substance.

different types of mixtures
different types of mixtures

A mixture is the physical mixing of two or more substances in any proportion. It is an impure material.
When two or more elements or compounds are mixed in any proportion such that their constituents retain their original properties, a mixture is produced. Various physical procedures, including distillation, filtration, and crystallisation, can be used to separate the contents of a mixture.

Components of a Mixture

A mixture consists of two constituents:

  1. Solute
  2. Solvent

Solute

Solute refers to the small component of a solution that is dissolved in the solvent.

Solvent

A solvent is the primary component of a solution that dissolves the solute. Also referred to as a dissolving media.

Examples of Mixture

Air is a mixture of oxygen, nitrogen, carbon dioxide, noble gases and water vapors.

different types of mixtures

A mixture of salt and water.

different types of mixtures

Soil is a mixture of sand,clay, mineral salt, water and air

different types of mixtures

A mixture of salt and sand.

different types of mixtures

Types of Mixture

2 types of mixture

  • Homogeneous mixture
  • Heterogeneous mixture

Homogeneous Mixture

A mixture that consists of only one phase is called a homogeneous mixture.

A homogeneous mixture has throughout the uniform composition

Examples of homogeneous mixture

  • A mixture of salt and water.
  • Air is a mixture of oxygen, nitrogen, carbon dioxide,
  • Noble gases and water vapors.

Heterogeneous Mixture

A mixture consisting of two or more visible different components is called a heterogeneous mixture.

Heterogeneous mixtures do not have uniform composition

Examples of the heterogeneous mixture

  • Oil floating on water.
  • A mixture of salt and sand.

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For additional information

Bad breath may have certain advantages. Garlic’s chemical composition is highly complex. Garlic has around 200 chemical components. People who consume a lot of garlic have a reduced risk of stomach cancer, heart disease, and stroke compared to those who consume little or no garlic.

Difference between Compound and Mixture

Difference between Compound and Mixture
Difference between Compound and Mixture

What is an Atomic Number?

Atomic Number z
Atomic Number

An atomic number is defined as the total number of protons present in the nucleus of an atom.

Atomic number ( Z ) = Number of Protons

Atomic Number Representation

Atomic Number z
Atomic Number z

Mass Number (A)

The mass number is defined as the total number of protons and neutrons in the nucleus of an atom.

Mass number ( A ) = Number of Protons + Number of Neutrons

The mass number is represented by the symbol A

mass number A
mass number A
mass number A

Finding atomic number (Z) & Mass Number (A) of Oxygen atom?

Atomic number ( Z ) = Number of Protons

Mass number ( A ) = Number of Protons ( Z) + Number of Neutrons (n)

Atomic number (Z) & Mass Number (A) of Oxygen

Atomic number (Z) & Mass Number (A)
Atomic number (Z) & Mass Number (A)
oxygen atom
oxygen atom

Atomic Number (Z) = 8 

 No of protons= 8

Mass Number (A) = 16

No of protons= 8

         +

No of neutrons = 8


How do you find the number of neutrons in an atom?

Atomic Number (Z) = 8

Mass Number (A) = 16

Number of neutrons ( n ) = Mass number ( A) – Atomic number (Z)

Number of neutrons ( n ) =  16 – 8                   

Number of neutrons ( n ) =   8             


Determining the number of protons and neutrons in an atom

Question

The atomic number of an element is 17 and the mass number is 35. How many protons and

 neutrons are present in the nucleus of an atom of this element?

Atomic number (Z) = 17     No of protons= 17

Mass Number  ( A ) =35     No of protons + No of neutrons = 35

Number of neutrons ( n ) =              35               –           17          

Number of neutrons ( n ) =              18          


relative atomic mass and amu

What is Relative atomic mass?

Relative atomic mass is defined as the mass of an atom of an element compared to the mass of a C-12 atom.

It is measured in either grams or amu. Consequently, the mass of one gram of an element represented in grams is known as the relative atomic mass.

Since an atom is an incredibly small particle, it is impossible to determine the precise mass of an element using a delicate balance. The chosen standard is carbon with a precise mass of 12g or 12amu.

Mass of one Carbon-12 atom=12amu

1 amu=mass of one C-12 atom/12

Now finding the relative atomic mass of hydrogen

8.4/100×12

=1.008 amu

EXAMPLE

One atom of sodium = 23 amu

 One atom of chlorine = 35.5 amu

One atom of calcium = 40 amu

Why?

Comparing the mass of an atom of an element with the mass of a C-12 atom.

Reason

The mass of an atom in grams or kilograms is an extremely small value, so measuring such a small mass is not possible.

For that purpose atomic masses are expressed by comparing with the mass of C-12 (standard atom).

Nowadays, the atom chosen as the standard for comparison is the C-12.

carbon atom
carbon atom

we measure,

Mass = Kilogram

Length=meter

Temperature = Kelvin

Time = second

Why is it called Carbon-12?

Why is it called Carbon-12?
Why is it called Carbon-12?

Unit of Relative atomic mass

Atomic mass unit ( amu )

Definition

One atomic mass unit (amu) is defined as a mass exactly equal to one-twelfth the mass of one C-12 atom.

Mass of one C-12 atom = 12 amu

amu =  mass of one C-12 atom / 12

Relative atomic masses of some elements.

Relative atomic masses of some elements.
Relative atomic masses of some elements.

AVERAGE ATOMIC MASS

The weighted average of atomic masses of naturally occurring isotopes of an element is known as average atomic mass.

EXPLANATION

In the majority of cases, the atomic mass of any element is rarely found to be in whole numbers. It is because most of the elements contain different isotopes and the relative atomic mass takes into account the natural abundance of each isotope.

Average Atomic Mass Formula

Average atomic mass = Atomic mass of 1st isotope × its % abundance/100 + Atomic mass of 2nd isotope × Its % abundance /100

Chemical Formula

The symbolic representation of a compound that shows elements in the compound and also the ratio of their atoms is called the chemical formula.

Chemical Formula
Chemical Formula of ammonia and water

Chemical Formulas Examples

Calcium Carbonate = CaCO3

Water = H2O

Sulphuric acid = H2SO4

Benzene = C6H6

Types of Chemical Formulas

  • Empirical Formula                      
  • Molecular Formula

Empirical Formula

The chemical formula that gives the simplest or the most reduced whole number ratio of atoms present in a compound is called the empirical formula.

Empirical Formula
c6h6 Empirical Formula

Empirical Formula of H2O2

The actual formula for hydrogen peroxide is H2O2 which shows that there is one hydrogen atom for every oxygen atom. Therefore the simplest ratio of hydrogen to oxygen is 1:1.So the empirical formula of hydrogen peroxide is HO.

Molecular Formula

  The chemical formula that gives the actual number of atoms present in one molecule of a compound is called the molecular formula.

The molecular formula could be derived from the empirical formula in the following way i.e

Molecular formula = n(Empirical formula) where n could be equal to 1,2,3,4,5…

FOR EXAMPLE

The empirical formula of benzene is CH so its Molecular Formula could be derived in the following way i.e

The molecular formula of Benzene =n(CH)

Here the value of n = 6

So Molecular formula of benzene=C6H6 

benzene molecular formula
COMPOUNDEMPIRICAL FORMULAMOLECULAR FORMULA
GLUCOSECH2OC6H12O6
ETHENECH2C2H4
empirical and molecular formulas

Question

5% of vinegar is acetic acid. This molecule has 2 carbon, 4 hydrogen, and 2 oxygen atoms. Write its empirical and molecular formulas.

Given:

Number of carbon atoms = 2

Number of hydrogen atoms = 4

Number of oxygen atoms = 2

Find out its empirical and molecular formulas

Solution:

C:    H:    O

2:    4:    2

molecular formula
empirical formula

Empirical formula   =   CH2O   

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Question

Caffeine ( C8H10 N4 O2) is found in tea and coffee. Write its empirical formula.

Given:

Molecular formula     = C8H10 N4O2        

Find out its empirical formula

Solution:

Caffeine  C8H10 N4 O2

Empirical formula   =   C4H5 N2O     

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Why do some compounds have the same empirical and molecular formula?

If the chemical formula cannot be further reduced, the empirical formula and molecular formula are same.

Why do some compounds have the same empirical and molecular formula?

Molecular mass

Molecular mass is defined as “ the sum of atomic masses of all the atoms present in the molecule “.

To find the molecular mass of a compound, you have to add up the atomic masses of all the atoms

In the compound.

For Example

Molecular mass of H2O

=2(atomic mass of H) + atomic mass of O

=2  (1)  +  16

=2 + 16
=18 amu

Molecular mass of NH3

NH3

=14 + 3 (1)

=14 +3
=17 amu

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Determine the molecular mass of glucose C6H12O6 which is also known as blood sugar.

Problem solving strategy

Multiply the atomic mass of carbon, hydrogen and oxygen by their subscripts and add.

SOLUTION

Molecular mass of C6H12O6 = 6(12.00) + 12(I.008) + 6(16.00)

= 180.096 amu

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Determine the molecular mass of naphthalene C10H8 which is used in mothballs

Problem solving strategy

Multiply the atomic mass of carbon, and hydrogen by their subscripts and add.

SOLUTION

Molecular mass of C10H8 = 10 (12 )+ 8 (1)

= 120 + 8

 = 128 amu


Difference between Molar mass and Molecular mass

Difference between Molar mass and Molecular mass
Molar mass and Molecular mass

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Formula unit

The smallest repeating unit of an ionic compound which shows the simplest ratio between its ions is called the formula unit.

Example

The simplest ratio between Mg and Cl in the crystal lattice of MgCl is 1:1 hence the formula unit of magnesium chloride is MgCl.


ION

When an atom loses or gains an electron it becomes a charged particle known as an ion.

how ions are formed
how ions are formed

EXPLANATION

Most of the time, an atom is electrically neutral, but when it takes or loses an electron, it acquires a charge and becomes an ion.

Types of Ions

There are two types of ions

  • Cation
  • Anion
types of ions
ion types

CATION

The charged specie that is formed by the loss of electrons is known as a cation.

The number of protons are greater than electrons in a cation

EXAMPLE

Mg+2 ,H+1

ANION

 The charged specie that is formed by the gain of electrons is known as an anion.

the number of electrons are greater than protons in anions.e.g Cl-1,O-2

Difference between Cation and Anion
Difference between Cation and Anion
difference between cation and anion

Formula Mass

The sum of atomic masses of all the atoms in the formula unit of a compound is called formula mass.

nacl formula amass
nacl

NaCl  Formula mass

=23 + 35.5

=58.5 amu

The simplest ratio between cations & anions in an ionic compound is called formula unit.

Formula mass of C3H6O

   = 12 x 3 + 1 x 6 + 16

   = 36 + 6 + 16

   = 58 amu

Formula mass of MgSO4

 = 24 + 32 + 16 x 4

 = 24 + 32 + 64

 = 120 amu


Molecular Ion

When a molecule gains or loses electrons, the resulting species is called a molecular ion.

how are molecular ions formed

Molecular ions that contain a positive charge are formed by the loss of an electron from neutral molecules.

Molecular ions having a negative charge are formed by the gain of an electron from neutral molecules

Examples of molecular ions

Positive molecular ions

Positive molecular ions are known as molecular cations E.g

O2+ ,CH4+ , H3O+ , NH4+

ch4+
ch4+
O2+
O2+

Negative molecular ions

Negative molecular ions are known as molecular anions E.g

SO4-2, OH


Free Radical

An atom or molecule having an unpaired electron in its valence shell is termed a free radical.

EXPLANATION

A free radical is formed by the homolytic fission of a molecule such that each atom in the molecule obtains an unpaired electron. A free radical has no charge and is represented by a  [.] on the symbol of the element. It is a highly reactive specie and cannot exist independently.

Reaction involving free radicals

Cl2 → 2Cl.

The chlorine-free radical will react with methane CH4 to form methyl free radical.

CH4 + Cl.→ CH3. + HCl

Now the methyl free radical reacts with another Cl2 molecule to form chloromethane and chlorine free radical

CH3. + Cl2→CH3Cl + Cl.

The reaction goes on until the formation of a stable product.

free radicals
free radicals

Free Radical Representation

free radicals

Free radical having odd no of valence electrons i.e. 1,3,5,7…..

How does free radical form?

In the presence of heat /light, homolytic breakage of the molecule occurs resulting in the formation of free radicals.

chlorine free radicals
chlorine free radicals

Free radicals have incomplete valence shell electrons. Due to this, they are unstable & short-lived.  


What is mole in Chemistry?

Mole

A mole is the mass of a substance that includes 6.023 x 1023 of the substance’s particles. The mole is the SI unit used to measure substance amounts.

mol is its symbol. By definition One mole of carbon-12 weighs 12 grams and contains 6.022140857 x 1023 carbon atoms.

OR Relative atomic mass, Formula mass, and Molecular mass expressed in grams is called a mole.

Examples

1 Mole of Oxygen =16g=6.023×1023 atoms

1 Mole of NaCl =58.5g=6.023×1023 formula units

1 Mole of water =18g=6.023×1023 molecules


Avogadros number

The quantity of units contained in a mole of any material is known as Avogadro’s number or Avogadro’s constant. The value is 6.022140857×1023. In accordance with the characteristics of the reaction and the material, the units might be electrons, ions, atoms, or molecules.

Therefore, the value would be as follows if you wanted to know how many particles there are in 3 moles of a substance:

= 3 x 6.023 x 1023

= 1.81 x 1024 particles

REPRESENTATION

It is represented by NA


Molar mass

The mass of one mole of particles ( atoms , molecules or formula units) expressed in grams is called molar mass.

mole in simple words
mole in simple words

For Example:

Mass of I mole of C- atom (6.022 x 1023  atoms)12 g

Molar mass of carbon atom =  12 g/ mol

Mass of I mole of H2O molecule (6.022 x 1023  molecules)18g                                                    

Molar mass of water molecule = 18g / mol

Mass of I mole of NaCl formula unit (6.022 x 1023  formula units) = 58.5g

Molar mass of NaCl formula unit = 58.5g /mol

How to Calculate molar mass:

HCl

=1 + 35.5
=36.5 g/mol

Ca(OH)2

=40 + 2 (16) +2(1)

=40 +32 +2
=74 g/mol

NH3

=14 + 3 (1)

=14 +3
=17 g/mol

CO2

=12 + 2 (16)

=12 +32
=44 g/mol

NaCl

=23 + 35.5
=58.5 g/mol


The mass of 5 moles of element X is 60g. Calculate the molar mass of this element. Also name the element.

Given data:

Mole of element X = 5 mol

Mass of element X = 60g

Required:

Molar mass of element X =  ?

Solution:

Using formula to find the molar mass :

mole formula

Putting values in formula :

so

mole formula

Thus the molar mass of element X is 12 g/mol

&

 the element X is carbon.


Mole Problems Practice

How do you calculate moles from molar mass?

1st Method

A technician weighs 40g of Sodium chloride (NaCl) . How many moles of formula units are in a sample?

Given data:

Mass of NaCl = 40 g

Required:

Moles of NaCl formula units =?

Solution:

Molar mass of NaCl = 23 + 35.5 = 58.5 g/mol

We know that:

mole formula
finding molar mass

2nd Method

A technician weighs 40g of Sodium chloride (NaCl) . How many moles of formula units are in a sample.

Given data:

Mass of NaCl = 40 g

Required:

Moles of NaCl formula units = ?

Solution:

Molar mass of NaCl = 23 + 35.5 = 58.5 g/mol

We know that :

58.5 g NaCl = 1 mole of NaCl formula units

40 g NaCl = 40/58.5 mole of NaCl formula units

   = 0.684 mol of NaCl formula units

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Gram Atomic Mass, Gram Molecular Mass and Gram Formula Mass                                       

Gram Atomic Mass, Gram Molecular Mass and Gram Formula Mass      
Gram Atomic Mass, Gram Molecular Mass and Gram Formula Mass      

GRAM ATOMIC MASS

Gram atomic mass is the term used to describe an element’s atomic weight when stated in grams. An element’s molar mass is defined as the mass of one mole in grams.

EXAMPLE

Helium, for instance, has a gram atomic mass of 4 g . Similarly sodium (Na), has a gram atomic mass of 22.99 grams and an atomic weight of 22.99 u. A mole of sodium thus weighs 22.99 g of atoms.

GRAM FORMULA MASS

The formula mass of an ionic compound expressed in grams is called gram formula mass

 It can be explained with the help of the following example

Formula mass of NaCl = 23 + 35.5

 = 58.5amu

Therefore, the gram formula mass of NaCl = 58.5g = mole of NaCl formula units.

 Formula mass of KCl = 39 + 35.5

 = 74.5amu. So, gram formula mass of KCl = 74.5g

GRAM MOLECULAR MASS

 The mass in grams of one mole of a molecule is known as the gram molecular mass. The molar mass and gram molecular mass are equivalent. The sole distinction is that the mass unit to be utilized is specified by gram molecular mass. The mass of a molecule can be expressed in either grams or grams per mole (g/mol).

EXAMPLES

Molecular mass of H2O = 2 x 1.008 + 16 = 18.016amu So, gram molecular mass of H2O = 18.016g Molecular mass of C6H12O6 = 6 x 12 + 12 x 1.008 + 16 x 6 = 180.096amu So, gram molecular mass of C6H12O6 = 180.096g.

Differentiate between gram atomic mass, gram molecular mass, and gram formula mass.

ANSWER

Statements

  1. In contrast to gram formula mass, which represents one mole of ionic formula units of a compound, gram atomic mass denotes one mole of atoms of an element. Gram molecular mass denotes one mole of molecules of a compound or an element that exists in a molecular state.
  2. Gram atomic mass contains 6.022 x 1023 atoms, gram molecular mass contains 6.022 x 1023 molecules whereas gram formula mass contains 6.022 x 1023 formula units
  3. Therefore one mole can be defined as formula mass, atomic mass, or molecular mass expressed in grams.

CHEMICAL CALCULATIONS

Fundamentals of Chemistry Problems Practice

Determine the molar masses of sodium, nitrogen, sucrose

Solution

Molar masses of sodium Na

1 mole of Na = 23g

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Nitrogen occurs as diatomic molecules.

Molar mass of Nitrogen N2

= 14 x 2

= 28amu

Therefore, mass of 1 mole of N2 = 28 g

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Molecular mass of Sucrose C12H22O11

= 12×12 + 1×22 + 16×11

= 144 + 22 + 176

Therefore, mass of 1 mole of sucrose = 342g

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2. Oxygen is converted to ozone  O3 during thunderstorms. Determine the mass of ozone if 9.05 moles of ozone is formed in a storm.

Ozone is a molecular substance. Determine its molar mass and use it to convert moles to mass in grams.

 9.05 moles of O3 ⎯⎯→ ? g of O3

 Solution:

 1 mole of O3 = 16 x 3 = 48 g

 1 mole of O3 = 48 g

 So, 9.05 moles of O3 = 48 g x 9.05

= 434.4g of O3

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3. When methane burns CO2 is formed is 0.25 moles of CO2 is formed what mass of CO2 is produced?

SOLUTION

Molar mass of CO2 = 12 + 16 x 2 = 44g

1 mole of CO2 = 44g of CO2

So, 0.25 moles of CO2 = 44 x 0.25 = 11g of CO2

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4. Calculate the moles of each of the following

A.Balloon filled with 5g of hydrogen

B.A block of ice that has a mass of 100g

SOLUTION

a) Molar mass of H2 = 1.008 x 2 = 2.016g

 1 mole of H2 = 2.016g

So, 2.016g of H2 = 1 mole of H2

1g of H2 = 1/2.016 moles of H2

5 gram of H2 =1÷2.016×5

5 gram of H2 = 2.48 Moles of H2

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b.1 Mole Of H2O =2×1.008+16

1 Mole of H2O =2.016+16

1Mole of H2O=18.016g

So 1 gram of H2O = 1÷18.016 moles

100 Gram of H2O= 1÷18.016×100 moles

100 grams of H2O=5.55 Moles of H2O

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5. Zn Is a metal that is used to galvanize steel to prevent corrosion. How many atoms are there in 1.25moles of Zn?

SOLUTION

1 mole of Zn contains = 23 6.022 x 1023 atoms

 1.25 moles of Zn contains = 6.022 x 1023 x 1.25  = 7.53 x 1023 Zn atoms

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6. Methane is one of the main components of natural gas . Calculate how many moles are in 0.5 moles of a pure sample of methane.

SOLUTION

1 mole of CH4 contains =  6.022 x 1023 molecules

So, 0.5 moles of CH4 will contain = 6.022 x 1023 x 0.5 = 3.011 x 1023 molecules

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7. Titanium is a metal that is used in rockets. Calculate the number of moles in a sample containing 3.011×1023atoms

SOLUTION

6.022 x 1023 atoms = 1 mole

3.011 x 1023Atoms→ ? mole

6.022×1023 atoms = 1 mole of Ti

1 Ti atom =1÷6.022×1023 moles of Ti

3.011×1023 Ti atoms = 1÷(6.022×1023)×3.011×1023 moles of Ti

=0.5 moles of Ti

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