Some Basic Concepts in Chemistry

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

SYNOPSIS
Basic Concepts in 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.