SOME BASIC CONCEPTS OF CHRMISTRY

DEFINITION: Chemistry is the branch of science that studies the composition, properties and

interaction of matter. Chemistry plays important role

In our daily life, industries, manufacturing fertilizers, dyes, polymers, drugs, soaps, detergents,

metals, alloys and other inorganic and organic chemicals,

in meeting human needs for food, health care products

drugs such as cisplatin and taxol , are effective in cancer therapy and AZT

(Azidothymidine) used for helping AIDS victims NATURE OF MATTER: Anything which has mass and occupies space is called matter.

International System of Units (SI) : The SI system has seven base units and they are listed in Table 1.1. Table 1.1

Base

Physical

Quantity

(symbol)

Length

(l)

Mass (m) Time

(t)

Electric

current

(I)

Thermodynamic

temperature

(T)

Amount of

substance

(n)

Luminous

intensity

(Iv)

Name of SI

Unit

(symbol)

metre

(m)

kilogram

(kg)

second

(s)

ampere (A) kelvin

(K)

mole (mol) cd

Prefixes used to indicate the multiples or submultiples of a unit-

Multiple deka-101 hecto-102 Kilo-103 mega-106 giga -109 tera-1012

Submultiple deci-10-1 centi-10-2 Milli-10-3 micro-10-6 nano-10-9 pico-10-12

SOLID

LIQUIDGAS

MATTER

Mixture

Homogeneous Mixture

Heterogeneous Mixture

Pure Substance

Elements Compound

Properties of Matter

PHYSICAL PROPERTIES OF MATTER- can bemeasuerd/obserevd without changing the composition ofthe substance

Examples : colour, odour, melting point, boiling point, density, mass, volume , temperature,length, area etc.

CHEMICAL PROPERTIES OF MATTER- are theosewhich require chemical change to occur for theirmeasurement.

Example: acidity, basicity, combustibility,

A measurement or Quantitative Observation

e.g; 6cm

a number e.g. 6 unint, e.g; cm

Has

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Mass of a substance is the amount of matter present in it while weight is the force exerted by gravityon an object. The mass of a substance is constant whereas its weight may vary from one place toanother due to change in gravity. The mass of a substance can be determined using an analyticalbalance.

The SI unit of mass is kilogram (kg)

1 kg = 1000 g

Volume is the space occupied by a matter

SI units of volume= (length)3 = m 3 , but often denoted as cm3 or dm3.

1L= 1000mL , 1000cm3 = 1 dm3

Density of a substance is its amount of mass per unit volume.

SI unit of Mass kg

SI units of density =----------------------- = -------- =kg m-3

SI Unit of Volume m3

common units of temperature — °C (degree celsius), °F (degree fahrenheit) and K (kelvin).

F= 9/5(0C) + 32

K= 0C + 273.15

Law of Conservation of Mass (Antoine Lavosier 1789): It states that matter can neither be created nor destroyed.

Law of Definite Proportions(Joseph Proust):a given compound always contains exactly the same proportion of elements by weight.

Law of Multiple Proportions ( Dalton in 1803) : "if two elements can 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".

Gay Lussac's Law of Gaseous Volumes (Gay Lussac 1808): "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 ( 1811): "equal volumes of gases at the same temperature and pressure should contain equal number of molecules. "

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The mass of 1 mole of a substance in grams is called its molar mass

1mole of carbon = 12 g Carbon = 6.02x1023 atoms of Carbon

1mole of water (H2O) = 18 g water (H2O) = 6.02x1023 molecules of H2O

1 mole of H2= 2g of Hydrogen (H2) = 22.4L of H2 at S.T.P =6.02x1023 molecules of H2

DALTON’S ATOMIC THEORY

( 1808, Dalton published ‘A New System of Chemical Philosophy’ in which he proposed :

Matter consists of indivisible atoms

All the atoms of a given element have identical properties &

mass.

Atoms of different elements differ in mass.

Compounds are formed when atoms of different elements combine in a fixed ratio.

Chemical reactions involve reorganisation of atoms. These are neither created nor destroyed in a chemical reaction.

6.02x1023 Particles

1 Mole

1 g atom of an elememnt

12 g of C 23g of Na

1 g molecule of a substance

44 g CO2 18 g of H2O

1 g formula wight os of a

substance

58.5 g of NaCl 100g CaCO3

Definition: One mole is the amount of a substance that contains as many particles or entities as there are atoms in exactly 12 g (or 0.012 kg) of the 12C isotope.

22.4 L of a Gas at N.T.P.

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Mass % of an element= mass of that element in 100 g of the compound

Limiting Reagent: The limiting reagent is the one that is totally consumed; it limits the reaction from continuing

because there is none left to react with the in-excess reactant.

From the reaction stoichiometry, the exact amount of reactant needed to react with another element can be

calculated. If the reactants are not mixed in the correct stoichiometric proportions (as indicated by the balanced

chemical equation), then one of the reactants will be entirely consumed while another will be left over.

Concentration of a sloution

Mas % or Weight %

mass of solute

mass %=----------------x100

mass of solution

Mole fraction

nA

xA=--------------

nA+nB

nB

xB=--------------

nA+nB

Molarity(M)

WB 1000

M=----------x-------------

MB vol of soln.(ml)

Molality(m)

WB 1000

M=--------x----------

MB wt solvent (g)

PERCENTAGE COMPOSITION: It is the mass of the component present in 100 parts of a

compound.

Mass of that element in the compound Mass % of an element = ----------------------------------------------x 100 Molar Mass of the compound

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