Chemistry Chapter (1) Introduction to Fundamentals Of Chemistry

Points to Remember

·      Chemistry:

Chemistry is the science dealing with composition of matter and the changes in composition that matter undergoes as well as energy and energy changes associated with matter.

·      Significant Figures:

These are the reliable digits in a number that are known with certainty.

·      Scientific Notation:

 In this system, numbers are written as the product of two factors. The first is a decimal number that usually ranges between 1 and 10 and the second is 10 raised to an appropriate power.

·      Atom:

An atom is the smallest unit of an element that can enter into a chemical reaction.

·      Elements:

 Elements are the simplest, least complex from of matter and they cannot be decomposed into simpler substances by chemical reactions.

·      Compound:

It is a distinct substance containing two or more elements chemically combined in a definite proportion by weight. Compounds can be decomposed chemically into simpler compounds or elements. Atoms of the elements in a compound are combined in whole number ratios never as fractional parts of atoms.

·      Molecule:

 Molecule is the smallest uncharged individual unit of compound formed by the union of two or more atoms.

·      Atomicity:

 It the number of atoms present in a molecule of a substance.

·      Ion:

 An ion is a charged particle.

·      Cat-ion:

Positively charged ion is called cat-ion.

·      Anion:

Negatively charged is called anion.

·      Chemical Formula:

The formula of a compound tells us which elements it is composed of and how many atoms of each element are formula unit.

·      Chemical Equation:

It is a shorthand expression for chemical reaction.

·      Relative Atomic Mass:

It is defined as the mass of one atom of the element compared with the mass of one atom of C-12.

·      Atomic Number:

 It is the number of electron or the number of proton in the atom.

·      Molecular Mass:

 It is defined as the sum of the atomic masses of the all the elements present in a molecule show by its molecular formula.

·      Molar Mass:

 The atomic mass in gram is the molar mass of an element and the molecular mass expressed in gram is the molar mass of a molecular substance.

·      Formula Mass:

It is the sum of atomic masses as given in the simplest formula of the substance.

·      Atomic Mass Unit:

One atomic mass unit equals exactly one twelfth the mass of a Carbon 12 atom.

·      Empirical Formula:

It is that formula which is found by experiment. It represents the simplest ratio of the combing atoms in a compound.

·      Molecular Formula:

A formula that expresses not only the relative number of atoms of each element but also the actual number of atoms of each element in one molecule of the compound is called molecular formula.

·      Mole:

 It is the amount of substance containing the same number of formula units as there are atoms in exactly 12 grams of carbon-12.

·      Avogadro’s number:

 In one gram mole of a substance, there are 6.02×10²³ particles. This huge number is called Avogadro’s number denoted by N_A.

·      Stoichiometry:

The area of chemistry that deals with the quantitative  relationship among reactants and products is known as stoichiometry.

·      Molar Volume:

 One mole of any gas at standard temperature and pressure occupies a volume of 22.4 dm³ is known as molar volume.

·      STP:

 Standard temperature is 0^oC or 273 A^o or 273 k: standard pressure is 1 atmosphere or 76cm or 760mm.

·      Limiting Reactant:

The reactant which is entirely consumed in a chemical reaction is called limiting reactant. Moles of product are always determined by moles of the limiting reactant.

Laws of Chemical Combination:

·       Law Of Conservation Of Mass:

It states that” Matter can neither be created nor be destroyed in the course of chemical action but it can change its form”.

·       Law of Definite Proportion:

 It states that all pure samples of the same chemical compound contain the same elements combined in the same proportion by weight.

·       Law Of Multiple Proportion:

It states that if the two elements A and B combine together to from more than one compound, then the several weight of A, which separately combine with fixed weight of B, are in simple ratio.

·       Law Of Reciprocal proportion:

It states that “If an element A combines with several other elements B,C and D, the weight of B, C and D  which combine with a fixed weight of A are the weight of  B, C and D which combine with each other simplest of those weights.

Sher Afzal Ranais

Author & Editor

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