Complete Chapter #2 (Chemical Combinations)

7/31/2019 Complete Chapter #2 (Chemical Combinations)

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2.1. DEFINATIONS

ATOMIC NUMBER (Z)

The sum of number of protons ORelectrons present in an atom are called Atomic Number.

EXAMPLE

The atomic number of: Hydrogen is 1 because it has one electron.

The atomic number of Carbon is 12 because it has twelve electrons.

ATOMIC MASS (A)

The sum of number of protons and neutrons present in an atom is called Atomic Mass.

EXAMPLEThe atomic mass of Hydrogen is one because it has one proton and there is no neutron in neutral

hydrogen.

FORMULA MASS

The sum of the atomic masses of all atoms in a formula unit of a substance is called Formula

Mass.

EXAMPLE

Na = 23x1 = 23 a.m.u.

Cl = 35.5 x 1 a.m.u.

Formula mass of NaCl = 58.5 a.m.u.

MOLAR MASS

Molar mass of a substance is its relative molecular mass / atomic mass expressed in grams is

called Molar Mass.

EXAMPLE

N = 14 x 1 = 14gm.

H = 1 x 3 = 3gm.

Molar mass of NH3 = 17gm.

CHEMICAL FORMULAEThe symbolic representation of molecules / atoms of a compound is called Chemical Formulae

of the compounds.

SOME CHEMICAL FORMULAE

The chemical formulae of some compounds are as under:

Sodium Chloride : NaCl Sodium Nitrate : NaNO3

CHEMICAL COMBINATIONS


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Silver Nitrate : AgNO3 Silver Chloride : AgCl Nitric Acid : HNO3 Hydrochloric Acid : HCl Water : H2O Hydrogen Peroxide : H2O2

TYPES OF CHEMICAL FORMULAE

There are two main types of Chemical Formulae.

Molecular Formulae. Empirical Formulae.

MOLECULAR FORMULA (M.F)

The formula which indicates the actual number of atoms of each element present in a molecule

is called Molecular Formula.

FORMULA

Molecular formula = n x Empirical formula.

EXAMPLES

The molecular formula of Glucose is C6H12O6. The molecular formula of Benzene is C6H6.

EMPIRICAL FORMULA (E.F): (SIMPLEST FORMULA)

The formula which indicates the minimum number of atoms of each element present in amolecule is called EMPIRICAL FORMULA.

FORMULA

Empirical formula=Molecular formula / n.

EXAMPLES

The empirical formula of Glucose is CH2O. The empirical formula of Benzene is CH.

MOLECULAR MASS

The sum of the atomic masses of all atoms present in the molecular formula is called Molecular

Mass.

FORMULA

Molecular mass= n x Empirical mass.

EXAMPLES

The molecular mass of Glucose is 180 a.m.u.

The molecular mass of Benzene is 78 a.m.u.


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EMPIRICAL MASS

The sum of the atomic masses of all atoms present in the empirical formula is called Empirical

Mass.

EXAMPLESThe empirical mass of Glucose (CH2O) is 30 a.m.u.

The empirical mass of Benzene (CH) is 18 a.m.u.

FORMULA

Empirical mass= Molecular mass / n.

AVAGADROS NUMBER (NA)

The number of particles (atoms, molecules, ions, formula unit) present in one mole of a

substance is known as Avogadros number (NA).

SYMBOL

Avogadros number is represented by NAor L.VALUE OF NA

Thevalue of Avogadros number is 6.02x1023

.

EXAMPLES

1 mole of hydrogen atom -1gm- 6.02x1023 atoms. 1 mole of oxygen molecule -32gm- 6.02x1023 molecules. 1 mole of carbon atom -12gm- 6.02x1023 atoms. 1 mole of water -18gm- 6.02x1023 molecules.

2.2. CHEMICAL REACTIONOR

CHEMICAL CHANGE

Any change, which alters the composition of a substance, is a Chemical Change / Chemical

Reaction.

OR

When one or more substances / reactants chemically react together and formed new product

(substance) is called Chemical Change /Chemical Reaction.

EXAPMLE

2Na + Cl2 2NaCl

TYPES OF CHEMICAL REACTIONS

There are five different types of chemical reaction.

Decomposition reaction. Addition reaction. Single replacement reaction.


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Double displacement reaction. Combustion reaction.

DECOMPOSITION REACTIONA reaction in which a chemical substance breaks down to form two or more simpler substances

is called Decomposition Reaction.

EXAPMLES

CaCO3 CaO + CO2

2KClO3 2KCl + 3O2

ADDITION REACTION

OR

COMBINATION REACTION

A reaction in which two or more substances combine to form a single substance is calledAddition Reaction.

EXAPMLES

CaO + CO2 CaCO3

2Na + Cl2 2NaCl

SINGLE REPLACEMENT (DISPLACEMENT) REACTION

A reaction in which one atom or group of atoms of a compound is replaced by another atom or

group of atoms is defined as Single Replacement / Displacement Reaction.

EXAPMLES

Zn + 2HCl ZnCl2 + H2Na + 2H2O 2NaOH + 2H2

Cl2 + 2KBr 2KCl + Br2

DOUBLE DISPLACEMENT (REPLACEMENT) REACTION

Areaction in which two compounds exchange their partners, so that two new compounds are

formed is known as Double Displacement / Replacement Reaction.

EXAPMLES

NaCl + AgNO3 NaNO3 + AgCl

CaCl2 + Na2CO3 2NaCl + CaCO3

COMBUSTION REACTION

A reaction in which substances react with either free oxygen or oxygen of the air, with the rapid

release of heat and flame, is called Combustion Reaction.

EXAPMLES

CH4 + 2O2 CO2 + 2H2O + H (Heat)

C + O2 CO2 + H (Heat)


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2.3. CHEMICAL_COMBINATIONWhen two or more chemicals combine together and formed new product is known as Chemical

combination.

EXAPMLENaCl + AgNO3 NaNO3 + AgCl

LAWS OF CHEMICAL COMBINATIONS

The chemical changes are governed by some empirical laws known as chemical combinations.

Law of conservation of mass. Law of constant composition OR Law of definite (fixed) proportion. Law of multiple proportion. Law of reciprocal proportion.

2.3.1. LAW_OF_CONSERVATION_OF_MASSINTRODUCTION

In 1785, a French Chemist Lavosier introduce a law is known as Law of Conservation of

Mass.

STATEMENT

Mass is neither created nor destroyed during chemical reaction.

EQUATION

2H2 + O2 2H2O

DIGRAMATICALLY

EXPLANATION

The law of conservation of mass may be demonstrated by the union of hydrogen (H2) and


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oxygen (O2) to form water. If the hydrogen and oxygen are weighed before they unite, it will be

found that there combined weight is equal to the weight of water (H2O).

2.3.2. LANDOLT EXPERIMENTINTRODUCTION

The practical verification of law of conservation was performed by German Chemist H. Landolt.

STATEMENT

The total mass of the substance before the reaction is equal to the total mass of the substances

after the reaction.

EQUATION

AgNO3 + HCl AgCl + HNO3

DIAGRAMATICALLY

EXPLANATIONLandolt took H-shaped tube and filled two limbs A and B. The tube was sealed so that the

material could not escape outside. The tube was weighed initially in a vertical position so that the

solutions should not intermix with each other. The reactants were mixed by inverting and

shaking the tube. The tube was weighed after mixing. He observed that weight remain same.

MASS ENERGY RELATIONSHIP

INTRODUCTION

The relationship between mass and energy was first proposed by Albert Einstein in1906.

STATEMENT

There is no detectable gain or loss of mass in a chemical reaction.EQUATION

The relationship between mass that is lost and the energy that is released is given by the

equation.

E=mc2

EXPLANATION


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In every chemical reaction, there will be a mass change. But this mass change is too small that no

one has yet been able to detect through weighing techniques.

2.3.3. LAW OF CONSTANT COMPOSITIONOR

LAW OF DEFINITE (FIXED) PROPORTION

INTRODUCTION

In 1799, a French chemist Louis Proust introduce a law is called Law of Constant

Composition.

STATEMENT

Different samples of the same compound always contain the same elements combinetogether in

the same proportion by mass.

EQUATION

Pb + 2S PbS2

2Pb + 2S PbS2 + Pb

DIAGRAMATICALLY

EXPLANATION

When 10gm of Lead reacts with 1.56gm of Sulphur it forms 11.56gm of Lead sulphide

Similarly, When 18gm of Lead reacts with 1.56gm of Sulphur it forms 11.56gm of Lead

sulphide and 8gm of Lead is left it means every sample of same compound, through prepared in

the laboratory or obtained from any other way it always contains same ratio parts by mass.

2.3.4. LAW OF MULTIPLE PROPORTIONINTRODUCTION

In 1803, English school teacher and Chemist John Dalton introduce a law is known as Law of

Multiple Proportion.

STATEMENT

If two elements combine to form more than one compound .The masses of one element that

combine with a fixed mass of the other element are in the ratio of small whole numbers or simple


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multiple ratios.

EQUATION

2C + O2 2COC + O2 CO2

EXPLANATION

The different masses of oxygen 16 and 32 which combine with fixed mass of C (12g) are in ratio

of [16:32], that is [1:2], which is simple whole number ratio, and obeys the law of multiple

proportion.

2.3.5. LAW OF RECIPROCAL PROPORTION

INTRODUCTION

In 1794, a chemist Ritcher enunciated a law is known as Law of Reciprocal Proportion.STATEMENT

When two different elements separately combine with the fixed mass of third element, the

proportion in which combine with the fixed mass of third element, the proportion in which they

combine with one another shall be either in the same ratio or some simple multiple of it.

EQUATION

C + O2 CO2

C + 2H2 CH4

2H2 + O2 2H2O

DIGRAMATICALLY


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EXPLANATION

When two elements carbon (C) and oxygen (O2) separately combine with hydrogen (H2) to form

methane (CH4) and water respectively it is very clear, that in methane (CH4) 3gm of carbon (C)

combine with 1gm of hydrogen (H2) and in water (H2O) 8gm of oxygen (O2) combine with thesame fixed mass i.e. 1gm of hydrogen (H2), now C and O combine with each other to form

carbon dioxide, they do so in the same proportion i.e. 12:32 = 3:8 parts by mass.

Similarly,

It is very clear that in the formation carbon disulphide (CS2) ,carbon (C) and sulphur(S) combine

in the ratio of (12:64) i.e. (3:16) which is simple multiple (3:8).


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SOME CHEMICAL FORMULAE AND THEIR NAMES

CHEMICAL NAME CHEMICAL FORMULAE COMMON NAME

Sodium carbonate Na2CO3 Soda Ash / Salt sodaSodium bicarbonate NaHCO3 Baking soda

Glucose C6H12O6 Dextrose

Benzene C6H6 Benzol

Ammonium chloride NH4Cl Salt ammoniac

Acetic acid CH3COOH Vinegar

Sodium hydroxide NaOH Caustic soda

Ammonia NH3 Windex Spirit of Hartshorne

Sulphuric acid H2SO4 Oil of vitriol / Battery acid

Aluminum oxide Al2O3 Alumina

Silver nitrate AgNO3 Lunar caustic

Hydrochloric acid HCl Spirit of saltPotassium nitrate KNO3 Salt peter

Sodium carbonatedecahydrated

Na2CO3.10H2O Washing soda

Ethyl alcohol C2H5-OH Spirit of wine / Grain alcohol

Nitrous oxide N2O Laughing gas

Magnesium Sulphate MgSO4 Epsom salt / Bitter salt

Calcium sulphate dihydrated CaSO4.2H2O Gypsum

Calcium sulphatehemihydrated

CaSO4.1/2H2O Plaster of paris

Methane CH4 Marsh gas / Natural gas

Nitric acid HNO3 Aqua fortisSodium chloride NaCl Rock salt / common salt

Zinc chloride ZnCl2 Killed spirits / Butter of zinc

Deuterium oxide D2O Heavy water

Calcium oxide CaO Quick lime / Burnt lime /Unslaked lime

Carbon dioxide CO2 Carbonic acid gas

Carbon disulphide CS2 Alcohol sulphuris

Ammonium hydroxide NH4OH Alkali volatile

Ammonium carbonate NH4CO3 Smelling salts

Balance the Chemical Equations.


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H2 + O2 H2O

AgNO3 + HCl AgCl + HNO3

CaCO3 CaO + CO2

KClO3 H, MnO2 KCl +O2CaO +CO2 CaCO3

Na +Cl2 NaCl

Zn + HCl ZnCl2 + H2

Na + H2O NaOH + H2

Cl2 + KBr KCl + Br2

NaCl + AgNO3 NaNO3 +AgCl

CaCl2 + Na2CO3 NaCl + CaCO3

CH4 + O2 CO2 + H2O


SO2 + O2 H, Pt SO3

Zn + H2SO4 ZnSO4 + H2


MgCO3 MgO + CO2

C2H2 + H2 C4H8

NO2 NO + O2

Na +O2 Na2O

CO + O2 CO2

Si + Cl2 SiCl4

C6H12O6 Fermentation C2H5-OH + CO2KNO3 KNO2 + O2

NaHCO3 Na2CO3 + H2O + CO2

CaCO3 + HCl CaCl2 + H2O + CO2

NH3 + O2 NO +H2O

C2H4 + H2 C2H6

BaCO3 BaO + CO2

N2 + H2 NH3

Ca + H2O Ca(OH)2 + H2

C2H5-OH + Na C2H5ONa + H2

H2 + Cl2 Bright sun light (hv) 2HCl

CH4 + Cl2 Sun light (hv) CH3Cl + HCl

H2O2 H2O + O2

C + 2H2 CH4


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PRACTICE NUMERICALS

NUMBER OF MOLES

i.

Calculate the number of moles in 25 gram of Carbon.ii. Calculate the number of moles in 50 gram of Water.iii. Calculate the number of moles in 34 gram of Ammonia.iv. Calculate the number of moles in 46 gram of Sodium.v. Calculate the number of moles in 168 gram of Sodium carbonate.vi. Calculate the number of moles in 36gram of Water.vii. Calculate the number of moles in 15 gram of Oxygen molecule.viii. Calculate the number of moles in 360 gram of Glucose.

MASS / WEIGHT BY MOLESi. Calculate the mass of 3 moles of Aluminum.ii. Calculate the mass of 4 moles of Water.iii. Calculate the mass of 2 moles of nitrogen gas.iv. Calculate the mass of 1 mole of Potash Alum.v. Calculate the mass of 4 moles of Carbon dioxide.

MOLECULAR MASSi. Calculate the molecular mass (a.m.u) of Water (H2O).ii. Calculate the molecular mass (a.m.u) of Hydrogen peroxide (H2O2).iii. Calculate the molecular mass (a.m.u) of Benzene (C6H6).iv. Calculate the molecular mass (a.m.u) of Sodium bicarbonate (NaHCO3)v. Calculate the molecular mass (a.m.u) of Water (H2O).

FORMULA MASS

i. Calculate the formula mass (a.m.u) of KNO3.ii. Calculate the formula mass (a.m.u) of Al2O3.iii. Calculate the formula mass (a.m.u) of NaCl.iv. Calculate the formula mass (a.m.u) of KCl.v. Calculate the formula mass (a.m.u) of MgCl2.

NUMBER OF ATOMS/MOLECULES

i. Calculate the number of atoms in 9 gram of Carbon.ii. Calculate the number of atoms in 26 gram of Sulphur.iii. Calculate the number of atoms in 96 gram of Sodium.iv. Calculate the number of molecules in 26 gram of sodium bicarbonate.v. Calculate the number of molecules in 400 gram of sodium bicarbonate.vi. Calculate the number of atoms in 34 gram of Ammonia.


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MASS OF ONE ATOM / ONE MOLECULEi. Calculate the mass of one atom of Carbon.ii. Calculate the mass of one atom of Chlorine.iii.

Calculate the mass of one molecule of Chlorine.iv. Calculate the mass of one molecule of Methane.

v. Calculate the mass of one molecule of Oxygen.MOLAR MASS

i. Calculate the molar mass of S8.ii. Calculate the molar mass of NH3.iii. Calculate the molar mass of CS2.iv. Calculate the molar mass of CH3COOH.v. Calculate the molar mass of CHCl3.


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Q. Fill in the blanks.1. The fundamental particle of an element is called______________.2. The sum of Electron OR Proton is called ______________.3. The sum of Proton + Neutron is called ______________.4. Electron, Proton and Neutron are in ______________.5. The formula which indicates actual no. of atom is called ______________.6. The formula which indicates simple atomic ratio is called ______________.7. The molar mass of water is ____ gm.8. The formula mass of Potassium Nitrate is______________.9. The value of Avogadros no. (NA) is ______________.10.The molecular formula of Glucose is______________.11.The molecular formula of Benzene is______________.12.The molecular mass of Glucose is______________.13.The molecular mass of Benzene is______________.14.When one or more chemical combine together and form new product is

called______________.

15.Combination of one or more chemicals is called______________.16.In 1785, French chemist______________ introduced Law of conservation of mass.17.Lavosier introduced a law called ______________.18.Mass is neither created nor destroyed is the statement of______________ chemist.19.18 a.m.u is the molecular weight / mass of______________.20.The increase in weight of Iron (Fe) on rusting because of its combination

with______________.21.When Red Oxide decomposes it form______________ and______________.22.German chemist ______________verify Law of conservation of mass.23.______________Chemist studied about fifteen different chemical reactions.24.In H-shaped tube Landolt filled Hydrochloric acid and______________.25.Landolt weighed H-shaped tube initially in a______________ position.26.In Landolt experiment reactants Silver Nitrate and Hydrochloric changed in to

______________and______________ product.

27.In 1906, ______________proposed relationship between mass and energy.28.Mass energy equation is______________.29.In mass energy equation (E) represents______________ in ergs.30.In mass energy equation (m) represents______________ in grams.31.In mass energy equation (C) is the velocity of light in ______________per second.32.The velocity of light is______________ cm/sec.33.There is no detectable gain or loss of mass in a chemical reaction is the statement of

______________.

34.In the end of 18th century, chemists showed any compound has______________ composition.


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Complete Chapter #2 (Chemical Combinations)