Class 11 chemistry ch 1

Class 11 chemistry chapter 1

SOME BASIC CONCEPTS OF CHEMISTRY

Chapter 1 Class 11

Chemistry:

Chemistry is the branch of science that deals with the composition,          

structure and properties of matter. Chemistry is called the science of atoms and molecule

Branches of Chemistry

• Organic  Chemistry  -This  branch  deals  with  study  of  carbon  compounds especially hydrocarbons and their derivatives.

 • Inorganic Chemistry-This branch deals with the study of compounds of all other elements except carbon. It  largely  concerns  itself with the  study of minerals found in the Earth's crust.

 • Physical  Chemistry-The  explanation  of  fundamental  principles  governing various chemical phenomena is the main concern of this branch. It is basically concerned with laws and theories of the different branches of chemistry.

 • Industrial Chemistry-The chemistry involved in industrial processes is studied under this branch.

•  Analytical Chemistry-This branch deals with the qualitative and quantitative analysis of various substances.

•  Biochemistry-This branch deals with the chemical changes going on in the bodies of living organisms; plants and animals.

•  Nuclear Chemistry-Nuclear reactions, such as nuclear fission, nuclear fusion, transmutation processes etc. are studied under this branch.

PROPERTIES OF MATTER AND THEIR MEASUREMENT

--Every substance has unique or characteristic properties. These properties can be classified into two

categories – physical properties and chemical properties.

Physical properties are those properties which can be measured or observed without changing the identity or the composition of the substance. E.g. colour, odour, melting point, boiling point, density etc.The measurement or observation of chemical properties requires a chemical change occur. e.g. Burning of Mg-ribbon in air

Chemical properties are characteristic reactions of different substances; these include acidity or basicity, combustibility etc.Many properties of matter such as length, area, volume, etc., are quantitative in nature.

Metric System was based on the decimal system.

The International System of Units (SI) 

The International System of Units (in French Le Systeme International d’Unites–

abbreviated as SI) was established by the 11th General Conference on Weights and Measures (CGPM fromConferenceGenerale des Poids at Measures). The SI system has sevenbase units

Mass and Weight-- Mass of a substance is the amount of matter present in it while weight is the force exerted by gravity on an object. The mass of a substance is constant whereas its weight may vary from one place to another due to change in gravity. The mass of a substance can be determined very accurately by using an analytical balance

Volume-- Volume has the units of (length)3. So volume has units of m3  or cm3  or dm3.A common unit, litre (L) is not an SI unit, is used for measurement of volume of liquids. 1 L = 1000 mL, 1000 cm3 = 1 dm3

Density: Density of a substance is its amount of mass per unit volume.SI unit of density = SI unit of mass/SI unit of volume = kg/m3 or kg m–3This unit is quite large and a chemist often expresses density in g cm–3.

Temperature--There are three common scales to measure emperature — °C (degree celsius), °F (degree Fahrenheit) and K (kelvin). Here, K is the SI unit.

K = °C + 273.15

Note—Temperature below 0 °C (i.e. negative values) are possible in Celsius scale but in Kelvin scale, negative temperature is not possible.

Scientific Notation 

In which any number can be represented in the form N × 10n Where n is an exponent having positive or negative values and N can vary between 1 to 10). e.g. We can write 232.508 as 2.32508 x102 in scientific notation. Similarly, 0.00016 can be written as 1.6 x 10–4.

Precision refers to the closeness of various measurements for the same quantity.

Accuracy is the agreement of a particular value to the true value of the result

Significant Figures 

The  reliability of  a  measurement  is  indicated  by  the  number  of  digits  used  to

represent it. To express it more accuratelywe express it with digits that are known with certainty. These are called as Significant figures. They contain all thecertain digits plus one doubtful digit in a number. Rules for determining the number of large numbers

 • All non-zero numbers are important.  For example, 6.9 contains two important numbers, and 2.16 contains three important components.  The decimal point does not specify the number of significant digits.

 • Zero becomes important when it comes between nonzero numbers.  For example, 2,003 contains four important changes, and 4.02 contains three important numbers.

 • In some cases, zeros are not significant.  For example, 0.002 contains one important number and 0.0045 has two important numbers.

 • All zeros in a number of struts are important.  For example, 16.0 contains three significant numbers and 16.00 has four significant numbers.  At the end of the decimal point, the zeros are mysterious.

 • In digital notation, the digital part represents the number of significant numbers.  For example, 0.00045 is reflected in scientific observations such as 4.5 x 10-4.  The number of important numbers in this number is 2, and the number of Avogadro (6,023 x 1023) is four.

 • The decimal point does not count the number of significant digits

 For example, the number 345601 contains six important numbers, but they can be written in different forms, as 345,601, 0.345601, or 3,45601 all have the same number.

 large numbers.

 Keep large numbers.  Round numbers

 The rounding procedure is used to maintain the required magnitude of importance

 Prepare:

 1. If the next number after the required number of significant digits is greater than 5, then the significant base value increases by one, and 4,317 is rounded to 4.32.

 2. If the number of characters in question is less than 5, then it is ignored, the previous important number remains unchanged, and surrounds 4,312 by 4.31.

 3. If the number is 5, then the last number or previous important number will be added by only one if the number is strange.  Even in the case of the indicator, the previous figure remains unchanged.  8,375 are rounded to 8.38 and rounded 8,365 to 8.36.

 Excessive analysis During calculations, it is generally necessary to convert units from one system to another.  This is called operator naming, unit factor, or dimensional analysis.

 For example, in SI 5 feet և 2 inches (Indian women height)

 points

 1 inch = 2.54 x 10-2 m

  Then 5 feet և 2 inches = 62 inches

 Physical classification of matter

 Properties:

 Solid

 A liquid

 Gas

 1. Size:

 clearly

 clearly

 Uncertain

 2. Composition

 clearly

 Uncertain

 Uncertain

 3. Between the molecules

 gravity

 very high

 Moderate

 Invisible / very:

 Low

 4. Planning:

 Molecules

 Regularly arranged

 Move freely

 Inside size

 Feel free to move everyone

 Where

 5. The internal molecular

 Void:

 Very small

 Slightly larger

 very big

 7. Pressure

 It is not clickable

 It is not clickable

 high:

 Compressible

 8. The expansion continues

 heating

 A little bit

 A little bit

 Lift wide

 9. Durability

 Very tough

 Non-static knowledge

 A liquid

 its not hard

 Known as liquid

 9. Liquidity

 It is impossible to flow

 Can flow

 Can flow

 10. Spread

 Can be separated

 Because of the kinetic energy of the liquid / gas

 Can be separated

 The propagation speed is very fast

 Can be separated

 The propagation speed is very fast

 Chemical classification of the substance ---

s.

 Ingredients:

 • Compounds always contain a certain percentage of the same elements in the mass.

 • The properties of the compounds differ completely from the elements that made up them.

 Homogeneous compounds.

 • Compounds are widely classified as organic and inorganic compounds.  Inorganic compounds are those that come from non-living sources, such as minerals.  For example, ordinary salt, marble, and limestone.  Organic ingredients are those that come from living sources, such as plants and animals.  They all contain carbon.  Organic compounds are oils, waxes, fats, etc.

 Mixtures:

 A mixture is a mixture of two or more elements or compounds of any ratio

 So the ingredients do not lose their identity.  Air is an example of a mixture

 There are two types of mixtures: monolithic and homogeneous.

 Heterogeneous mixtures

 It has the same composition throughout the sample.  The components of these mixtures cannot be observed under a strong microscope.  These are also called solutions.  Examples of homogeneous mixtures are air, sea water, gasoline, money, etc.

 Heterogeneous mixtures

 It consists of two or more parts (stages) that have different combinations.  These mixtures have different levels of separation, and can be seen with the naked eye, such as sand and salt, chalk powder in water, etc.

 Community Committee

 Comprehensive Conservation Law

 (Presented by Antoine Lavoisier in 1789).

 It says that matter (mass) cannot be created and destroyed.

 Law of certain proportions or the law of permanent training.

 This law was proposed by Louis Prost in 1799, which states:

 "Chemical compounds always consist of the same elements that are combined in the same proportion, regardless of the method of preparation or its source

 taken.  "

 The law of multiple lineage proposed by Dalton in 1803, says this law: each other:

 Jay-Lussac's law on gas volumes

 (Presented by Guy Lusac in 1808).

 According to this law, when gases are combined or produced in a chemical reaction, they do so with a small amount of volume if all gases are at the same temperature and pressure.

 For example, H2 (g) + Cl2 (g) --- → 2HCl (g)

 1V 1V 2V:

 All reagents and products have a simple ratio of 1: 1: 2:

 Avogadro's Law

 (Awarded in 1811 by Avogadro)

 According to this law, at the same temperature and pressure, equal quantities of gases must contain equal amounts of molecules.

 Dalton's atomic theory

 • All materials are made of small indivisible particles called atoms.  Atoms of the same element have the same properties of ice, size, mass, etc.

 • Atoms of different elements are different in all respects.

 Corn is the smallest unit involved in chemical formulations.

 Atoms combine to form a simple integer to form complex atoms called molecules.

 Atoms cannot be formed, separated or destroyed during any chemical or physical change.

 Atoms and molecules

 The smallest component can be independent or it can be

 Existence is called an atom, and the smallest particle of substances capable of self-existence is called a molecule.

 The molecules are classified as homogeneous and heterogeneous.  Homosexual molecules consist of atoms of the same element and heterogeneous atomic molecules.

 Different atoms of different elements contain different atoms (the number of atoms in an element's molecule), such as monatomic, two-atom, tri-atomic, and polyatomic.

 Atomic mass unit

 A unit of mass of one atom is defined as the mass equal to one tenth of the mass of a carbon-12 atom.  And one month = 1.66056 x 10-24 g.

 Today, "amu" has been replaced by "u", which is known as a single block.

 Atomic mass

Atomic mass of an element is defined as the average relative mass of an atom of an

element as compared to the mass of an atom of carbon -12 taken as 12.

Gram Atomic Mass

The quantity of an element whose mass in grams is numerically equal to its atomic

mass. In simple terms, atomic mass of an element expressed in grams is the gram atomic mass or gram atom. For example, the atomic mass of oxygen = 16 amu Therefore gram atomic mass of oxygen = 16 g

Molecular Mass

Molecular mass of a substance is defined as the average relative mass of its molecule

as compared to the mass of an atom of C-12 taken as 12. It expresses as to how many times the molecule of a substance is heavier than 1/12th of the mass of an atom of carbon.

For example, a molecule of carbon dioxide is 44 times heavier than 1/12th of the mass of an atom of carbon. Therefore the molecular mass of CO2 is 44 amu.

It is obtained by adding the atomic masses of all the atoms present in one molecule.

Gram Molecular Mass 

A quantity of substance whose mass in grams is numerically equal to its molecular

mass is called gram molecular mass. In simple terms, molecular mass of a substance expressed in grams is called gram molecular mass.

e.g., the molecular mass of oxygen = 32 amu

Therefore, gram molecular mass of oxygen = 32 g

Formula Mass-

Sum of atomic masses of the elements present in one formula unit of a compound. It

is used for the ionic compounds.

Mole Concept.

Mole is defined as the amount of a substance, which contains the same number of chemical units (atoms, molecules, ions or electrons) as there are atoms in exactly 12 grams of pure carbon-12.

A mole represents a collection of 6.022 x1023( Avogadro's number) chemical units..The mass of one mole of a substance in grams is called its molar mass.

Molar Volume

The volume occupied by one mole of any substance is called its molar volume. It is

denoted by Vm. One mole of all gaseous substances at 273 K and 1 atm pressure occupies a volume equal to 22.4 litre or 22,400 mL. The unit of molar volume is litre

per mol or millilitre per mol

PERCENTAGE COMPOSITION— 

The mass percentage of each constituent element present in any compound is called

its percentage composition

Mass % of the element=Mass of element in 1 molecule of the compound    x 100

Molecular mass of the compound

Empirical Formula and Molecular Formula—

An empirical formula represents the simplest whole number ratio of various atoms present in a compound. E.g. CH is the empirical formula of benzene.

The molecular formula shows the exact number of different types of atoms present in a molecule of a compound. E.g. C6H6 is the molecular formula of benzene.

Relationship between empirical and molecular formulae

The two formulas are related as Molecular formula = n x empirical formula

Chemical Equation-

Shorthand representation of a chemical change in terms ofsymbols and formulae of

the substances involved in the reaction is called chemical equation..

The substances that react among themselves to bring about the chemical changes are known as reactants, whereas the substances that are produced as a result of the

chemical change, are known as products

Limiting Reagent- The reactant which gets consumed first or limits the amount of product formed is known as limiting reagent

Reactions in Solutions-- The concentration of a solution can be expressed in any of

the following ways.

1.    Mass Percent is the mass of the solute in grams per 100 grams of the solution.

A 5 % solution of sodium chloride means that 5 g of NaCl is present in 100g of the solution.

2.     Volume percent is the number of units of volume of the solute per 100 units of the volume of solution.

A 5 % (v/v) solution of ethyl alcohol contains 5 cm3 of alcohol in 100 cm3 of the solution

3.     3.     Molarity of the solution is defined as the number of moles of solute dissolved per litre (dm3) of the solution. It isdenoted by the symbol M. Measurements in Molarity can change with the change in temperature because solutionsexpand or contract accordingly.

Molarity of the solution = No. of moles of the solute         = n

Volume of the solution in litre       V

The Molarity of the solution can also be expressed in terms of mass and molar mass

Molarity of the solution =                                          Mass of the solute

Molar mass of the solute X volume of the solution in liter

In terms of weight, molarity of the substance can be expressed as:

Molarity equation

To calculate the volume of a definite solution required to prepare solution of other

molarity, the following equation is used:

M1V1 = M2V2, where M1= initial molarity, M2= molarity of the new solution, V1=

initial volume and V2= volume of the new solution.

4.    Molality- Molality is defined as the number of moles of solute dissolved per 1000 g (1 kg) of solvent. Molality is expressed as 'm'.

5.     Mole Fraction is the ratio of number of moles of one component to the total number of moles (solute and solvents) present in the solution. It is expressed as

'x'.

Mole fraction of the solute =              Moles of the solute

Moles of solute  +  Moles of solvent

Mole fraction of the solvent =              Moles of the solvent

Moles of solute  +  Moles of solvent

Mole fraction of the solute + Mole fraction of solvent = 1