1-What is matter
Ans:- Anything that has mass and occupies space is called matter. Every matter is particulate. They are made of particles. When any matter is further broken down, It splits and splits. Lastly a time appears when it stops to split and a smallest unit is appear, This smallest unit is known as atom. A matter is made up of many atoms.
When many atoms combine together, they form molecule.
When many molecules combine together, They form matter.
2- What is an atom?
Ans:- The smallest unit
of matter that cannot be further divided into any other particles without
releasing of electrically charged particles. It is the smallest unit of matter
that has the characteristic properties of chemical element.
1-When two or more same types of atoms are combined together, They will form molecule of element.
2-When two or more different types of atoms are combined together, They will form molecule of compound.
Around 500 BC an Indian philosopher Maharishi Kanad firstly gave a hindi name of matter that is Padarth. He said that every padarth is made of small particles called parmanu.
To prove this He performed an activity with rice grains
He took some rice grains and start chewing. After some time, He found that rice grains divided into very fine particles and these fine particles stopped to break down. He gave a name of these fine particles as parmanu.
According to maharishi kanad’s atomic theory
1-Everything can be sub divided
2-Overtime subdivision leads to creation of parmanu which is the smallest unit of matter.
3-Parmanu is indivisible, It cannot be further divide.
4- parmanu is not seen by naked eyes.
Ø In 18th century Two other greek philosopher Leucippus and Democritus support the theory of atoms that is given by Maharishi Kanad. They called the parmanu as atom.
4-Theory of Pakudha Katyayama
Pakudha katyayama is an Indian philosopher. He gave the laws of atom first. He states that atoms may not exist in to be free state but may exist in combined state in the form of molecules.
Question- Make the molecule of oxygen , Make the molecule of carbon di-oxide., Make the molecule of water
5-What is chemical reaction?
When two or more substances combine to form an entirely different product . This type of combination is called chemical reaction.
Ex:- When acid combines with base than they form salt
Acid + base – salt
When hydrogen combines with oxygen form water.
Hydrogen + Oxygen - water
6-Law of chemical combination
Antoine L. Lavoisier is the father of chemical science. He lead the foundation of chemical science by establishing two important laws of chemical combination. The two laws of chemical combination that were established by Antonie L. Lavoisier and Joseph L. Proust are
1- Laws of conservation of mass
2-Laws of constant proportions
7-Law of conservation of mass
Law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction. In any chemical reaction, the total mass of the reactants is equal to the total mass of the product
For proving this law he performed an experiment
Experiment
He took 5% solution of sodium carbonate in conical flask. and he also took 5% of copper sulphate in a tast tube. Now he hanged the tast tube in the flask carefully. See that the solutions do not get mixed. Put a cork on the flask. Weigh the flask with its contents carefully. Now tilt and swirl the flask, so that the solutions get mixed. Now weight again
Observation
When the solution of sodium carbonate is mixed with copper sulphate, than chemical reaction occurs and new substance Sodium sulphate and Copper Carbonate is formed. But the mass of new substances donot change
Sodium carbonate + copper sulphate → sodium sulphate + copper carbonate CuSO4 + Na2CO3 → CuCO3 + Na2SO4
Result
Mass of reactant substance = Mass of product substance
Hence mass can neither be created nor destroyed in a chemical reaction. In any chemical reaction, the total mass of the reactants is equal to the total mass of the product.
Numerical-1
When 4.2g of sodium hydrogen carbonate( NaHCO3 ) is added to a solution of hydrochloric acid (HCl ) weighing 10.0g. It is observed that 2.2g of Carbon dioxide ( CO2) is released into the atmosphere. The residue left behind it found to weigh 12.0g. show that these observations are in agreement with the law of conservation of mass.
solution:- The reaction is
Sodium hydrogen carbonate +hydrochloric acid → Sodium chloride + water + Carbon dioxide
Mass of reactants = mass of Sodium hydrogen carbonate + mass of hydrochloric acid
= 4.2g + 10.0g
=14.2g
Mass of products = mass of carbon dioxide + mass of residue
=2.2g + 12.0g
=14.2g
As mass of reactants = mass of products
There is no loss or gain of mass during the reaction.
Hence the given observation prove the law of conservation of mass
Numerical-2
What mass of silver nitrate will react with 5.85g of sodium chloride to produce 14.35g of silver chloride and 8.5 g of sodium nitrate if the law of conservation of mass is true?
Solution:- The reaction is
Silver nitrate + Sodium chloride → Silver chloride + Sodium nitrate
mass of sodium chloride =5.85g
mass of silver chloride=14.35g
mass of sodium nitrate=8.5g
If the law of conservation of mass is true.
Total mass of reactants = Total mass of products
mass of silver nitrate + mass of sodium chloride = mass of silver chloride + mass of sodium nitrate
mass of silver nitrate + 5.85g = 14.35g + 8.5g
mass of silver nitrate = 17g
8-Law of constant proportion
Law of constant proportion states that chemical compounds are made up of elements that are present in a fixed ratio by mass. The law of constant proportions is often referred to as Proust's law or as the law of definite proportions
Ex:- Pure water will always contain hydrogen and oxygen in a fixed mass ratio. The ratio of hydrogen and oxygen in pure water by mass is 1 : 8. hence in 9 gram of water, 1 gram is hydrogen and 8 gram of oxygen.
Numerical-1
Copper oxide was prepared by two different methods. In one case, 1.75 g of metal gave 2.19g of oxide. In the second 1.14g of the metal gave 1.43g of oxide. Show that the given data illustrates the law of constant proportion
Solution-
In case 1
Mass of copper = 1.75g
Mass of copper oxide = 2.19g
% of copper in copper oxide = mass of copper / mass of copper oxide ✕ 100
= 1.75 / 2.19 ✕ 100
= 79.9%
% of oxygen = 100 - 79.9
= 20.1%
In case 2
Mass of copper = 1.14g
Mass of copper oxide = 1.43g
% of copper in copper oxide = mass of copper / mass of copper oxide ✕ 100
= 1.14 / 1.43 ✕ 100
= 79.7%
% of oxygen = 100 - 79.7
= 20.3%
In first case % of copper is approx 80% and % of oxygen is appeox 20%. In second case the result is same. Hence the given data illustrates the law of constant proportion.
Numerical-2
Calculate the mass of carbon present in 2g of carbon dioxide
Solution:- Carbon dioxide (CO2) contains C and O in the fixed proportion by mass which is 12 : 32 that is 3 : 8.
This means that 3g of Carbon combine with 8g of oxygen to form 11g of CO2
In other word,
mass of carbon contained in in 11g of CO2 = 3g
mass of carbon contained in in 1g of CO2 = 3 / 11g
mass of carbon contained in in 2g of CO2 = (3 / 11 ) ✕ 2g
= 0.545g
Numerical-3
Calcium carbonate (CaCO3) contains 40% of calcium, 12% of carbon and 48% oxygen by mass. Knowing that law of constant composition holds good. calculate the mass of the constituent elements present in 2g of Calcium carbonate.
Solve-
% of calcium in calcium carbonate = 40%
% of carbon in calcium carbonate = 12%
% of oxygen in calcium carbonate = 48%
Ratio of calcium , carbon and oxygen in calcium carbonate = 40 : 12 : 48
=10 : 3 : 12
Sum of their ratio = 10 + 3 + 12
= 25
The mass of calcium in 25g calcium carbonate = 10g
The mass of calcium in 1g calcium carbonate = 10 / 25g
The mass of calcium in 2g calcium carbonate = ( 10 / 25 ) ✕ 2g
= 0.8g
The mass of carbon in 25g calcium carbonate = 3g
The mass of carbon in 1g calcium carbonate = 3 / 25g
The mass of carbon in 2g calcium carbonate = ( 3 / 25 ) ✕ 2g
= 0.24g
The mass of oxygen in 25g calcium carbonate = 12g
The mass of oxygen in 1g calcium carbonate = 12 / 25g
The mass of carbon in 2g calcium carbonate = ( 12 / 25 ) ✕ 2g
= 0.96g
After the discovery of laws of chemical combination, It was essential to give a suitable explanation of these laws
Dalton's atomic theory
John Dalton was a British chemist. He provided the basic theory about the nature of matter. This theory is known as Dalton's atomic theory. It stated that all matters is made up of small indivisible particles known as atoms.
According to Daltons atomic theory, All the substances are made up of atoms which are indivisible and indestructible. Atoms of an element are same in size and mass. The atoms of different elements are found in different size and mass.
Postulates of Dalton's atomic theory
1- All matters are made of very tiny particles called atoms.These particles take part in chemical reaction.
2- Atoms are indivisible particles, which cannot be created or destroyed in a chemical reaction. In chemical reaction atoms combined to form a new substance. Existing atoms cannot be destroyed and new atoms cannot be formed.
3-Atoms of same element are similar in properties , mass and size but Atoms of different elements have different properties, mass and size.
4- Atoms cannot be divided into smaller particles.
5- Atoms of different elements can combine with each other in fixed ratio to form compound.
6- Atoms can be rearranged, combined or separated in chemical reactions.
Limitations / Drawbacks of Dalton's atomic theory
1- Atom is no longer considered as the smallest indivisible masses.
2-Atoms of the same element may have different masses.
( There are certain elements whose masses of atoms are different but atomic numbers are same. These elements are called isotopes. Ex:-There are three isotopes of carbon that is C -12, C-13 , C-14 )
C-12 = In this carbon atom, atomic number is 6 but atomic mass is 12
C-13 = In this carbon atom, atomic number is 6 but atomic mass is 13
C-14 = In this carbon atom, atomic number is 6 but atomic mass is 14
3- Atoms of the different element may have same masses.
Different elements that have different atomic number but same atomic mass are called isobars. Ex:- K-40 and Ca-40
K-40 = In K-40, atomic number is 19 and atomic mass is 40
Ca-40 = In Ca-40, atomic number is 20 and atomic mass is 40
4- Substances made up of the same kind of atoms may have different properties.
Ex:- Diamond and graphite
What is an atom?
Ans:- The smallest particle of an element which may or may not be capable of free existence is called an atom. It is the smallest particle that take part in a chemical reaction.
Write about the characteristics of atom on the basis of size.
Ans:- Atoms are very tiny particles. They can not be seen by general microscope. They are only seen by a special type of microscope called STM ( Scanning tunneling microscope ).
Atoms are considered to be spherical in shape.
The size of atoms are expected in the term of radii called atomic radii. The radii of an atom is usually expressed in nanometers ( nm ).
1nm = 1 / 109 m
or 1nm = 1 ✕ 10-9 m
What is atomic radii?
Ans:- The distance between nucleus to the outer cell of an atom is called atomic radii.
atomic radii of hydrogen = 10-10 m
atomic radii of molecule of water = 10-9 m
atomic radii of molecule of haemoglobin = 10-8 m
atomic radii of grain of sand = 10-4 m
atomic radii of ant = 10-3 m
atomic radii of apple = 10-1 m
Symbols used to represent atoms of different elements
What is the symbol of elements?
Ans:- Symbol is the short method of representing any thing. In the case of element, symbol is a short method to representing the full name of an element.
Dalton was the first scientist who used the symbol for elements. He used circle with other symbols to represent symbol of elements.
Berzilius was the first who suggested that the symbols of an element be made from one or two letters of the name of the element.
In the beginning, the names of elements were derived from the name of the place where they were found for the first time. for ex:- The name copper was taken from cyprus.
Some name of element were taken from specific colours. For ex:- gold was taken from the english word meaning yellow
Why do we use symbols to represent elements?
Ans:- We use symbols to represent elements because
1- Symbol of elements make representation easier and faster.
2- Symbol of elements are universal. They are same throughout the world. Hence they are easier to identify.
3- Symbol of elements make easier the chemical formula to write.
Write all the ways by which the symbol of elements derived
Ans:- The ways by which the symbol of elements derived are
1- Symbol of some elements are derived from the first alphabet of its name. This alphabet is always written in capital.
Ex:- Name of element symbol
Hydrogen H
Boron B
Carbon C
2- Symbol of some elements are derived from the first two alphabets of its name. where its first alphabet is always in capital.
Ex:- Name of element symbol
Helium He
lithium Li
Beryllium Be
3- Symbol of some elements are derived from the first alphabet and third alphabet of its name. where its first alphabet is always in capital.
Ex:- Name of element symbol
Chlorine Cl
magnesium Mg
Argentum Ag
4- Symbol of some elements are derived from its Latin name.
Ex:- Name of element symbol Latin name
Iron Fe Ferrum
Sodium Na Natrium
Lead Pb Plumbum
What is IUPAC?
Ans:- IUPAC is an international scientific organisation which approves names of elements , symbols and units. The full form of IUPAC is ( International union of pure and applied chemistry )
Atomic mass
What is atomic mass?
Ans:- The total mass of one atom of any given element is called its atomic mass. The unit of atomic mass is unified atomic mass unit . It is denoted by u. most of the atomic mass of a substance is made up of protons and neutrons. there for it is almost equal to the mass number.
What is atomic weight?
What is atomic mass of a hydrogen atom?
Ans:- 1.67 × 10-24 g
What is atomic mass of an oxygen atom?
Ans:- 2.6561 × 10-23g
Who was Avogadr?
Avogadro was an Italian scientist. His full name is Lorenzo Romano Amedeo Carlo Avogadro. He state that equal volumes of gases under the same conditions of temperature and pressure will contain equal number of molecules.
What is avogadro's number?
Ans:- The number of units in one mole of any substance is called avogadro's number or avogadro's constant. It is equal to 6.022140857 × 1023
What is the value of avogadro's number?
Ans:- 6.022 × 1023
How can we find atomic mass of one atom of any element in gram? Write formula.
Ans:- We can find atomic mass of one atom of any element in gram by the help of atomic mass that is given in periodic table and avogadro number
atomic mass of one atom = Atomic mass of periodic table / avogadro number
What is atomic mass of one atom of C-12 element?
Ans:- 12 amu or 12 u
1 amu = mass of C-12 atom / 12
1 amu = 1/12th part of mass of one C-12 atom
Why C-12 atom is taken as reference atom( standard unit ) for finding atomic mass?
Ans:- C-12 atom is taken as reference atom for finding atomic mass because the atom of C-12 element is neither a less reactive nor a highly reactive. It is also found in abundant in nature
How can we find atomic mass of one atom of an element
Ans:- We can find atomic mass of one atom of an element by relating it with the mass of one atom of C-12. C-12 is the standard element which help in finding atomic mass
Ex:- find the atomic mass of one atom of hydrogen in amu.
Solve:- mass of one atom of hydrogen = 1.67 × 10-24 g
Mass of one atom of C-12 = 1.66 × 10-24 g
Atomic mass of one atom in amu = 1.67 × 10-24 g / 1.66 × 10-24 g
= 1 amu approx
Molecule
What is molecule?
A group of two or more than two atoms which are held together strongly by some kind of attractive forces is called molecule.
The attractive forces which holding the atoms together is called chemical bond
A molecule is the smallest particle of an element or compound which can exist freely under ordinary conditions and shows all the properties of that substances.
How many types of molecules? name them
There are two types of molecule
1- molecule of element
2- molecule of copound
What is molecule of element?
When one, two or more than two atoms of the same element exist as one species in free state. this is called molecule of element.
What is monoatomic molecule?
When molecules contain one and only one atom, they are called monoatomic molecules.
Ex:- Argon, Helium etc,
The molecule of noble gases like helium, neon etc, exist in single atom.
The symbols for their molecules and atoms are same.
What is diatomic molecule?
When molecules contain two atoms, they are called diatomic molecules.
Ex:- oxygen, hydrogen, nitrogen, chlorine
What is triatomic molecule?
When molecules contain three atoms, they are called triatomic molecules.
Ex:- Ozone, It is represented by O3
What is tetratomic molecule?
When molecules contain four atoms, they are called tetratomic molecules.
Ex:- Phosphorus, It is represented by P4
What is polyatomic molecule?
When molecules contain more than four atoms, they are called polyatomic molecules.
Ex:- sulphur, It is represented by S8
What is atomicity?
The number of atoms present in one molecule of the substance is called atomicity.
What is molecule of compound?
When two or more than two atoms of different elements combined together in a definite proportion by mass to form a species that can exist freely is called molecule of compound.
What is diatomic molecule of compound?
Those molecule of compound that has two atoms is called diatomic molecule of compound.
Ex:- Hydrogen chloride ( HCl ) , Carbon monoxide ( CO ) etc.
What is triatomic molecule of compound?
Those molecule of compound that has three atoms is called triatomic molecule of compound.
Ex:- water ( H2O ) , Carbon dioxide ( CO2 ) , Sulphur dioxide ( SO2 ) etc.
What is tetratomic molecule of compound?
Those molecule of compound that has four atoms is called tetratomic molecule of compound.
Ex:- Hydrogen peroxide ( H2O2 ) , ammonia ( NH3 ) etc.
What is miolecular mass?
molecular mass of a substance represents the number of times the molecule of that substance is heavier than 1/12th of the mass of an atom of C-12 isotope. The molecular mass of a substance is the sum of the atomic masses of all the atoms in a molecule of the substance. The relative mass of a molecule is expressed in atomic mass units or (u )
Numerical-1
Calculate the relative molecular mass of water
Solve:- Atomic mass of hydrogen = 1u
atomic mass of oxygen = 16u
So molecular mass of water , which contains two atom of hydrogen and one atom of oxygen =
2 ⅹatomic mass of hydrogen + 1 ⅹmolecular mass of oxygen
= 2 ⅹ1 + 1 ⅹ16
= 18u
Numerical-2
Calculate the relative molecular mass of HNO3
Solve:- Atomic mass of hydrogen = 1u
atomic mass of nytrogen = 14u
atomic mass of oxygen = 16u
So molecular mass of HNO3 , which contains one atom of hydrogen one atom of nytrogen and three atoms of oxygen = 1 ⅹatomic mass of hydrogen + 1 ⅹatomic mass of nytrogen + 3 ⅹatomic mass of oxygen
=1 ⅹ1 + 1 ⅹ14 + 3 ⅹ16
= 1+ 14 + 48
= 63 u
Numerical-3
Calculate the relative molecular mass of Al2(SO4)3
Solve:- Atomic mass of aluminium = 27u
atomic mass of sulphur = 32u
atomic mass of oxygen = 16u
So molecular mass of Al2(SO4)3 , which contains two atoms of aluminium three atoms of sulphur and twelve atoms of oxygen = 2 ⅹatomic mass of Al + 3 ⅹ[ atomic mass of sulphur + 4 ⅹatomic mass of oxygen ]
=2 ⅹ27 + 3 ⅹ[ 32 + 4 ⅹ16 ]
= 54 + 3[32 +64 ]
= 54 + 3 ⅹ 96
= 342 u
What is an ion?
Ans:- An atom or group of atoms which carries positive or negative charge is called an ion.
There are two types of ion
1- cation - The ion which carrying positive charge is called cation.
Ex:- Na+, Mg2+ , Al3+ etc
2- anion - The ion which carrying negative charge is called anion.
Ex:- O2-, H-
The ion which consisting of only single atoms are called monoatomic ion.
Ex- Na+, Mg2+ , Al3+ , O2-, H- etc
The ion which consisting a group of atoms is called a polyatomic ion.
Ex:- OH-1 , SO42-
What is ionic compound?
Ans:- A compound that is formed by two ions ,that mean The compounds consisting of cations and anions are called ionic compound.
or
A compound that is formed by a metal and a non metal are called ionic compound. In ionic compound elements donate or accept the atom
Ex:- sodium chloride
What is molecular compound?
Ans:- A compound that is formed by two non-metals are called molecular compound. In molecular compound elements share there atoms to form compound
Ex:- hydrochloric acid
Writing chemical formula of compunds
What is chemical formula of a compound?
Ans:- Chemical formula of a compound is a symbolic representation of its composition.What is valency?
Ans:- The number of electrons gained, loss or shared by an atom of an element to achieve the nearest noble gas configuration is called valency.
Ex:- The valency of sodium is 1, The valency of magnesium is 2, The valency of chlorine is 1 etc.
Rules for writing formula
1- The valencies or charges on the ion must balance.
2- When a compound consists of a metal and a non-metal, the name or symbol of the metal is written first. Ex:- calcium oxide ( Cao ) , copper oxide ( CuO )
3- In compounds formed with polyatomic ions, The number of ions present in the compound is indicated by enclosing the formula of ion in a bracket and writing the number of ions out side the bracket. Ex:- Mg(OH)2
Rules for writing formula of simple molecular compounds
The simple compounds which are made up of two different elements are called binary compounds. while writing the chemical formpla for compounds, we write the constituent elements and their valencies. We must crossover the valencies of the combining atoms.
Hydrogen chloride is a molecular compound. Molecular compound has valency but no charge. in molecular compound two nonmetals react. Some other example of molecular compounds are carbon tetra chloride ( CCl4 ) , carbon dioxide ( CO2 )
Rules for writing formula of simple ionic compounds
The simple compounds which are made up of two different elements are called binary compounds. while writing the chemical formpla for ionic compounds, we write the symbol of cation first followed by the symbol of anion. Than their charges are criss-crossed to get the formula.
Magnesium chloride is an ionic compound. Ionic compound has charge . in ionic compound one metal and one nonmetal react. Some
other example of ionic compounds are aluminium oxide ( Al2O3 )
, calcium oxide ( CaO ) , sodium nitrate ( NaNO3 )
, calcium hydroxide ( Ca(OH)2 ) , Sodium carbonate ( Na2CO3 ) , Ammonium sulphate ( (NH4)2SO4 )
Note:- The formula of calcium hydroxide is Ca(OH)2 and not as CaOH2 We must brackets when we have two or more of the same ions in the formula. Here the bracket around OH with a subscript 2 indicate that there are two hydroxyl (OH ) groups joined to one calcium atoms. In other words , there are two atoms each of oxygen and hydrogen in calcium oxide.
Formula unit mass
The formula unit mass of a substance is a sum of the atomic masses of all atoms in a formula unit of compound.
Formula unit mass is calculated in the same manner as we calculate the molecular mass. The only difference is that we use the word formula unit for those substances whose constituent particles are ions.
Ex:- Find the formula unit mass of sodium chloride
Solve:- Chemical formula of sodium chloride = NaCl
Atomic mass of sodium = 22u
atomic mass of chlorine = 34u
So formula unit mass of NaCl , which contains one atom of sodium one atom of chlorine = 1 ⅹatomic mass of sodium + 1 ⅹatomic mass of chlorine
=1 ⅹ22 + 1 ⅹ34
= 22+ 34
= 56 u
Find the formula unit mass of calcium chloride
Solve:- Chemical formula of calcium chloride = CaCl2
Atomic mass of calcium = 40u
atomic mass of chlorine = 34u
So formula unit mass of CaCl2 , which contains one atom of calcium and two atoms of chlorine = 1 ⅹatomic mass of calcium + 2 ⅹatomic mass of chlorine
=1 ⅹ40 + 2 ⅹ34
= 40 + 78
= 118 u
Gram atomic mass
When atomic mass expressed in gram is called gram atomic mass of that element.
or
The amount of an element having mass equal to gram atomic mass is called gram atom of the element. It is represented by g atom.
जब किसी सब्सटांस के पर्टिकुलर अमाउंट का मास ग्राम में जब उस सब्सटांस के एटॉमिक मास के बराबर हो जाये , तब वह मास उस सब्सटांस का ग्राम एटॉमिक मास कहलाता है
When the mass of a particular substance in gram is equal to their atomic mass, than this mass is called gram atomic mass of this substance.
Ex:- जब ऑक्सीजन के x अमाउंट का मास ग्राम में नुमेरिकाली ऑक्सीजन के एटॉमिक मास के बराबर हो जायेगा तब वह ऑक्सीजन का ग्राम एटॉमिक मास कहलायेगा
Q- What is the gram atomic mass of oxygen?
Solve:-Atomic mass of oxygen in amu = 16 amu
∴ gram atomic mass of oxygen = 16 gram
Q- What is the difference between atomic mass and gram atomic mass of oxygen?
Ans:-The difference between atomic mass and gram atomic mass is
The atomic mass of of oxygen is 16 amu, it shows that the mass of one atom of oxygen is 16 amu. but the gram atomic mass of oxygen is 16 gram, It shows that 16 gram is the mass of 6.022 × 1023 atoms of oxygen.
Note:- This rule of atomic mass and gram atomic mass is applicable on every element
Gram molecular mass
When moleculr mass expressed gram is called gram molecular mass of that substance.
or
The amount of substance having mass equal to its gram molecular mass is called one gram molecule or (g molecule ) of the substance
Q- What is the gram molecular mass of water?
Solve:-molecular mass of water in amu = 18 amu
∴ gram molecular mass of oxygen = 18 gram
Q- What is the difference between molecular mass and gram molecular mass of oxygen?
Ans:-The difference between molecular mass and gram molecular mass is
The molecular mass of of water is 18 amu, it shows that the mass of one molecule of water is 18 amu. but the gram molecular mass of water is 18 gram, It shows that 18 gram is the mass of 6.022 × 1023 molecule of water.
Note:- This rule of molecular mass and gram molecular mass is applicable on every molecule of element or compound.
Mole concept
1 Dozen = 12 units, 1 score = 20 units, 1 gross = 144 units
1 kg = 1000g, 1 quintal = 100kg, 1 tonne = 10000 kgh
There are two ways to measure the amount of substance.
1- by calculating mass
2- by calculating number
to measure mass we can use weighing machine and some units like kg, gram, quintal etc.
To calculating number of articles we can use some units like dozen, score etc.
जैसे chemistry के बाहर आर्टिकल होते हैं वैसे ही chemistry के अंदर particle होता है।
Atoms, molecules, ions, electrons, protons and neutrons all are known as particles in chemistry
We measure quantity of articles by finding their mass or number similarly in chemistry we measure quantity of particles by finding their mass or number.
We can measure an atom by mass to find their atomic mass and we can measure a molecule by mass to find their molecular mass.
To find the number of atoms or molecules, we can use avogadro number. The avogadro number is 6.022 × 1023
The avogadro number is represented by Na or N0 ( N0 is said to N not )
6.022 × 1023 = 1 mole
or
1 mole = 6.022 × 1023 particles ( 1 mole of a substance is equal to 6.022 × 1023 particles of that substance. )
1 mole of hydrogen = 6.022 × 1023 atoms of hydrogen 1 mole of oxygen = 6.022 × 1023 atoms of oxygen 1 mole of water = 6.022 × 1023 molecule of water
1 mole of hydrogen = 1 g of hydrogen 1 mole of oxygen = 8 g of oxygen 1 mole of water = 18 g of water
1 gram of hydrogen = 6.022 × 1023 atoms of hydrogen 1 gram of oxygen = 6.022 × 1023 atoms of oxygen 1 gram of water = 6.022 × 1023 molecule of water
What is the difference between 1u and 1g in hydrogen?
Ans:- 1u is the mass of 1 hydrogen atom but 1g is the mass of 6.022 × 1023 hydrogen atoms
The mass of 1 mole of hydrogen atom is equal to the gram atomic mass
1 mole = 6.022 × 1023 atoms
1 g of hydrogen atom = 6.022 × 1023 atoms
1 gram of H atom = gram atomic mass
1 mole = gram atomic mass
The mass of mole is known as molar mass
The molar mass of hydrogen = 1 mole of hydrogen
The molar mass of hydrogen = gram atomic mass of Hydrogen
∴1 mole of hydrogen = 6.022 × 1023 atoms of hydrogen = 1 gram of hydrogen
similarly
1 mole of oxygen = 6.022 × 1023 atoms of oxygen = 16 gram of oxygen
Note- These method works similarly on each element
Lets talk about molecule
1 mole of H2O = 6.022 × 1023 molecule of H2O = 18 gram of H2O
1 mole of H2O = 18 gram of H2O
The molar mass of H2O = gram molecular mass of H2O
calculate the mass of 1 mole of oxygen atom in gram
1 mole of oxygen atom = 6.022 × 1023 atom
one atom of oxygen contains 8 protons and 8 neutrons
mass of 1 proton = 1.67 × 10-24
mass of 1 neutron = 1.67 × 10-24
∴ mass of 1 atom of oxygen = mass of 8 proton + mass of 8 neutron
= 8 × 1.67 × 10-24 g + 8 × 1.67 × 10-24 g
= 1.67 × 10-24 g ( 8 + 8 )
= 16 × 1.67 × 10-24 g
∴ mass of 6.022 × 1023 atoms = 16 × 1.67 × 10-24 × 6.022 × 1023 g
= 16 × 10.05 × 10-1 g
= 16 × 1 g
=16 g
∴ mass of 1 mole of oxygen atom = 16 gram
∴ the mass of 1 mole of oxygen = gram atomic mass
∴ molar mass = gram atomic mass
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