Some Basic concepts of Chemistry
Chemistry is the branch of science that studies the composition , properties and interaction of matter.
Importance And Scope Of Chemistry
1. In supply of food.
2. In contribution to better health and sanitation.
3. In saving the environment.
4. In increasing comforts,pleasures and luxuries.
5. In transport and communication.
6. In industry.
7. In war.
8. As nuclear or atomic energy.
Matter Anything that occupies space,has mass and presence of which can be felt by any one oe more of our five senses.
Physical Classification Of Matter
Solid A substance is said to be solid,if it has definite volume and a definite shape e.g. sugar , wood , gold etc.
Liquid A substance is said to be liquid,if it has a definitevolume but no definite shape. They take up the shape of the vessel in which they are put e.g. water, milk, oil etc.
Gaseous A substance is said to be gaseous if it neither has a definite volume nor etc. a definite shape e.g. hydrogen , oxygen , air etc.
* These states are interconvertible by changing the conditions of temperature and pressure as follows :
SOLID ↔ LIQUID ↔ GAS
Chemical Classification
Mixture : It contains more than one kind of pure substance in any ratio.
Homogeneous Mixtures : It has uniform composition and identical properties throughout.
Heterogeneous Mixtures : It has non-uniform composition and different phases can be seperated from each other by disticnt boundaries.
Element : A pure substance that contains only one kind of particles.
Compounds : Pure substances containing more than one kind of elements or atoms.
Atom : It is the smallest particle of an element which may be or may not be capable of independent.
Molecule : It is the smallest particle of an element or a compound which can exist freely.
Significant Figures : These are meaningful digits which are known with certainty.
Rules For Determining The Number Of Significant Figures
1. All non-zero digits are significant.
2. Zeros preceding to first non-zero are not significant.
3. Zeros between two non-zero digits are significant.
4. Zeros at the end or right of a number are significant provided they are on the right side of the decimal points.
Laws Of Chemical Combinations
Law Of Conservation Of Mass : Matter can neither be created nor destroyed.
Law Of Definite Proportions : A chemical compound is always found to be made up of same elements combined together in the same fixed proportion by mass.
Law Of Multiple Proportions : When two elements combine to form two or more chemical compounds,then the masses of one of the elements which combine with a fixed mass of the other,bear a simple ratio to one another.
Gay Lussac's Law Of Gaseous Volumes : When gases combine or are produced in a chemical reaction they do so in a simple ratio by volume provided all gases are at same temperature and pressure.
Avogadro Law : Equal volumes of gases at the same temperature and pressure should contain equal no. of molecules.
Dalton's Atomic Theory : John dalton in 1808 put forward a theory. The main points of this theory are
1. Matter consists of indivisible atoms.
2. All the atoms of a given element have identical properties including identical mass.
3. Compounds are formed when atoms of different elements combine in a fixed ratio.
4. Chemical reactions involve reorganisation of atoms.
Atomic Mass : It is the no. of times an atom of that element is heavier than an atom of carbon taken as 12.
One Atomic Mass Unit : It is equal to 1/12th of the mass of an atom of carbon-12 isotope.
Molecular Mass : It is the sum of atomic masses of the elements present in a molecule.
Mole : One mole is the amount of a substance that contains as many particles as there are atoms in exactly 12 g of 12C isotope.
Molar Mass : The mass of one mole of a substance in grams.
Emperical Formula : It represents the simplest whole no. ratio of various atoms present in a compound.
Molecular Mass : It represents the exact no. of different types of atoms present in a molecule of a compound.
Molecular Formula : n * Emperical Formula
Molecular Mass : 2 * Vapour Density
Stiochiometry & It's Calculations : Stoichiometry deals with the calculation of mass,volumes, and no . of particles of the reactants and products involved in a chemical reaction e.g.
2C6H6 + 7O2 -------> 4CO2 + 6H2O
The coefficients 2 for C6H6,7 for O2,4 for CO2 and 6 for H2O are called stoichiometric coefficient.
Limiting Reagent : The reactant which gets consumed,limits the amount of the product formed.
Reactions In Solutions
Solution : Ahomogeneous mixture of two or more chemically non-reacting substances,the relative amounts of which can be varied upto a certain limit.
The concentration pf a solution can be expressed in a no. of ways :
Mass Percent : Mass percentage of a solute in a solution is the mass of the solute in grams present in 100 g of the solution.
Mole Fraction : It is the ratio of no. of moles of a particular component to the total no. of moles of the solution.
Molarity : It is defined as the no. of moles of solute in 1 litre of the solution.
Molarity : It is defined as the no. of molres of the solute dissolved in 1 kg of the solvent.
Normality : It is defined as the no. of gram equivalents of the solute present per litre of the solution.
No. Of Gram Equivalent = Mass Of Solute In Grams / Equivalent Mass Of Solute
Equivalent Mass Of An Acid = Molecular Mass Of Acid / Basicity
Equivalent Mass Of Base = Molecular Mass Of Base / Acidity
Equivalent Mass Of A Salt = Molecular Mass Of Salt / Total Positive Valency Of Metal Atoms
Basicity : No. of displacable H+ ions present in one molecule of acid.
Acidity : No. of displacable OH- ions present in one molecule of base.
Molarity Equation : If a solution having molarity M1 and volume V1 is diluted to volume V2 so that new molarity is M2,we have M1V1 = M2V2
Normality Equation : If a solution having Normality N1 and volume V1 is diluted to volume V2 so that new Normality is N2,we have N1V1 = N2V2
Importance And Scope Of Chemistry
1. In supply of food.
2. In contribution to better health and sanitation.
3. In saving the environment.
4. In increasing comforts,pleasures and luxuries.
5. In transport and communication.
6. In industry.
7. In war.
8. As nuclear or atomic energy.
Matter Anything that occupies space,has mass and presence of which can be felt by any one oe more of our five senses.
Physical Classification Of Matter
Solid A substance is said to be solid,if it has definite volume and a definite shape e.g. sugar , wood , gold etc.
Liquid A substance is said to be liquid,if it has a definitevolume but no definite shape. They take up the shape of the vessel in which they are put e.g. water, milk, oil etc.
Gaseous A substance is said to be gaseous if it neither has a definite volume nor etc. a definite shape e.g. hydrogen , oxygen , air etc.
* These states are interconvertible by changing the conditions of temperature and pressure as follows :
SOLID ↔ LIQUID ↔ GAS
Chemical Classification
Homogeneous Mixtures : It has uniform composition and identical properties throughout.
Heterogeneous Mixtures : It has non-uniform composition and different phases can be seperated from each other by disticnt boundaries.
Element : A pure substance that contains only one kind of particles.
Compounds : Pure substances containing more than one kind of elements or atoms.
Atom : It is the smallest particle of an element which may be or may not be capable of independent.
Molecule : It is the smallest particle of an element or a compound which can exist freely.
Significant Figures : These are meaningful digits which are known with certainty.
Rules For Determining The Number Of Significant Figures
1. All non-zero digits are significant.
2. Zeros preceding to first non-zero are not significant.
3. Zeros between two non-zero digits are significant.
4. Zeros at the end or right of a number are significant provided they are on the right side of the decimal points.
Laws Of Chemical Combinations
Law Of Conservation Of Mass : Matter can neither be created nor destroyed.
Law Of Definite Proportions : A chemical compound is always found to be made up of same elements combined together in the same fixed proportion by mass.
Law Of Multiple Proportions : When two elements combine to form two or more chemical compounds,then the masses of one of the elements which combine with a fixed mass of the other,bear a simple ratio to one another.
Gay Lussac's Law Of Gaseous Volumes : When gases combine or are produced in a chemical reaction they do so in a simple ratio by volume provided all gases are at same temperature and pressure.
Avogadro Law : Equal volumes of gases at the same temperature and pressure should contain equal no. of molecules.
Dalton's Atomic Theory : John dalton in 1808 put forward a theory. The main points of this theory are
1. Matter consists of indivisible atoms.
2. All the atoms of a given element have identical properties including identical mass.
3. Compounds are formed when atoms of different elements combine in a fixed ratio.
4. Chemical reactions involve reorganisation of atoms.
Atomic Mass : It is the no. of times an atom of that element is heavier than an atom of carbon taken as 12.
One Atomic Mass Unit : It is equal to 1/12th of the mass of an atom of carbon-12 isotope.
Molecular Mass : It is the sum of atomic masses of the elements present in a molecule.
Mole : One mole is the amount of a substance that contains as many particles as there are atoms in exactly 12 g of 12C isotope.
Molar Mass : The mass of one mole of a substance in grams.
Emperical Formula : It represents the simplest whole no. ratio of various atoms present in a compound.
Molecular Mass : It represents the exact no. of different types of atoms present in a molecule of a compound.
Molecular Formula : n * Emperical Formula
Molecular Mass : 2 * Vapour Density
Stiochiometry & It's Calculations : Stoichiometry deals with the calculation of mass,volumes, and no . of particles of the reactants and products involved in a chemical reaction e.g.
2C6H6 + 7O2 -------> 4CO2 + 6H2O
The coefficients 2 for C6H6,7 for O2,4 for CO2 and 6 for H2O are called stoichiometric coefficient.
Limiting Reagent : The reactant which gets consumed,limits the amount of the product formed.
Reactions In Solutions
Solution : Ahomogeneous mixture of two or more chemically non-reacting substances,the relative amounts of which can be varied upto a certain limit.
The concentration pf a solution can be expressed in a no. of ways :
Mass Percent : Mass percentage of a solute in a solution is the mass of the solute in grams present in 100 g of the solution.
Mole Fraction : It is the ratio of no. of moles of a particular component to the total no. of moles of the solution.
Molarity : It is defined as the no. of moles of solute in 1 litre of the solution.
Molarity : It is defined as the no. of molres of the solute dissolved in 1 kg of the solvent.
Normality : It is defined as the no. of gram equivalents of the solute present per litre of the solution.
No. Of Gram Equivalent = Mass Of Solute In Grams / Equivalent Mass Of Solute
Equivalent Mass Of An Acid = Molecular Mass Of Acid / Basicity
Equivalent Mass Of Base = Molecular Mass Of Base / Acidity
Equivalent Mass Of A Salt = Molecular Mass Of Salt / Total Positive Valency Of Metal Atoms
Basicity : No. of displacable H+ ions present in one molecule of acid.
Acidity : No. of displacable OH- ions present in one molecule of base.
Molarity Equation : If a solution having molarity M1 and volume V1 is diluted to volume V2 so that new molarity is M2,we have M1V1 = M2V2
Normality Equation : If a solution having Normality N1 and volume V1 is diluted to volume V2 so that new Normality is N2,we have N1V1 = N2V2