Some Basic Concepts in Chemistry

Some Basic Concepts in Chemistry PDF Notes, Important Questions And Synopsis

Some Basic Concepts in Chemistry PDF Notes, Important Questions and Synopsis

SYNOPSIS
Basic Concepts of Chemistry

Classification of Matter:

Properties of Matter:
Physical properties: Colour, odour, melting point, boiling point, density
Chemical properties: Acidity, basicity, combustibility

The International System of Units (SI):

Physical quantity	Symbol for quantity	Name of SI unit	Symbol for SI unit
Length	l	metre	m
Mass	m	kilogram	kg
Time	t	second	s
Electric current	I	ampere	A
Thermodynamic temperature	T	kelvin	K
Amount of substance	n	mole	mol
Luminous intensity	I_o	candela	Cd

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.

Temperature:

Thermometer with the Celsius scale is calibrated from 0 to 100.
The Fahrenheit scale is represented between 32 and 212.
Negative values of temperature are not possible on the Kelvin scale.

Significant figures:

Significant figures are meaningful digits which are known with certainty.

Laws of Chemical Combination

Law of conservation of mass: Matter can neither be created nor be destroyed.
Law of definite proportions: given compound always contains the same proportion of elements by weight.
Law of multiple proportions: If two elements can combine to form more than one compound, the masses of one element which
combine with a fixed mass of the other element are in the ratio of small whole numbers.
Gay-Lusaac’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 the same temperature and pressure.
Avogadro’s law: Equal volumes of gases at the same temperature and pressure should contain equal number of molecules.

Atomic mass

One atomic mass is defined as mass exactly equal to 1/12th the mass of one carbon-12 atom.

Molecular mass

Molecular mass is the sum of atomic masses of the element present in the molecule.

Formula mass

The formula mass of a molecule is the sum of the atomic weights of the atoms in the empirical formula of a compound.

Mole

One mole is the amount of substance which contains as many particles or entities as there are atoms in exactly 12 g of the C-12 isotope.

Molar mass

The mass of one mole of a substance in grams.

Empirical formula and molecular formula

An empirical formula represents the simplest whole number ratio of various atoms present in a compound.
A molecular formula shows the exact number of different types of atoms present in a molecule of a compound.

Stoichiometry

Stoichiometry deals with the relationship between reactants and products involved in a chemical reaction to determine desired quantitative data.

Limiting reagent

A limiting reagent in a chemical reaction is a substance which is totally consumed when the reaction is completed.

Concentration terms

Molarity (M): Number of moles of a solute present in per unit volume of solution.
Molality (m): Number of moles of a solute present in one kilogram of a solvent.
Normality (N): Number of gram equivalents of a solute present in per unit volume of solution.
Mole fraction: Ratio of the number of moles of a particular component to the total number of moles of the solution.
Mass per cent or weight per cent (w/w%): Gram of solute present in 100 gram of solution.
Volume by volume per cent (v/v%): mL of solute present in 100 mL of solution.
Weight by volume per cent (w/v%): Gram of solute present in 100 mL of solution.