engineering chemistry

Question 1

Define isotope

Answer 1

Atoms of the same element having different atomic number but the same mass number

Question 2

Define isobars

Answer 2

Atoms of different elements having the same mass number but different atomic number

Question 3

Mass number

Answer 3

Protons + neutrons in the nucleus of an atom

Question 4

Atomic number

Answer 4

Number of protons in the nucleus of an atom.

Number of electrons revolving around the nucleus of an atom.

Question 5

Charge of a cation

Answer 5

Positive

Question 6

Charge of an anion

Answer 6

Negative

Question 7

When electron is transferred from sodium atom to chlorine atom the sodium atom becomes

Answer 7

Cation

Question 8

The chlorine atom gains an electron hence becomes,

Answer 8

An anion

Question 9

Oxidation

Answer 9

Process that involves the loss of electrons.

Eg;
Na loses an electron(e-) to become a cation Na+.

Question 10

Reduction

Answer 10

A process that involves gaining/addition of an electron.

Eg; Cl gains an electron to become an anion Cl-

Question 11

Octet theory

Answer 11

All the elements with an unstable or incomplete electronic configuration have a tendency to attain the stable electronic configuration of the nearest inert gas configuration either by complete transfer of valence electron from one atom to another or by mutual sharing of valence electron between the atoms

Question 12

Covalent bond

Answer 12

Formed when a pair of electrons is shared between two atom: Ammonia (NH3)

Question 13

Ionic/ Electrovalent bond

Answer 13

Complete transfer of one or more electrons from one atom to another

Question 14

Molecule

Answer 14

A Molecule is the smallest particle of matter(element or a compound)
that can exit freely.

Question 15

Homoatomic molecule

Answer 15

The molecule is made up of two or more atoms of the same elements.
Molecules of Chlorine(Cl2), Oxygen(O2), and Hydrogen(H2) contain only
two atoms of same kind. So they are called as Homoatomic molecules.

Question 16

Heteroatomic molecules

Answer 16

The molecule is made up of more than two of more atoms of different
elements.

Question 17

MOLECULAR MASS:

Answer 17

Molecular mass of an element or a compound is the ratio between the
mass of one molecule of the element or the compound and the mass of 1/12
part of a carbon Atom.

Molecular
Mass of an element or compound = Mass of one molecule of an
Element ÷ 1/12 part by mass of carbon

Question 18

Mole

Answer 18

The mole is a unit of measurement used in chemistry to
express amounts of a chemical substance. One mole of any substance
contains Avogadro number of particles i.e.,6.023X10^23 particles.

Question 19

AVOGADRO’S HYPOTHESIS

Answer 19

Avogadro’s Hypothesis states that, “Equal volumes of all gases contain the
same number of molecules at the same temperature and pressure”

Question 20

Relationship between Molecular Mass & Vapour Density

Answer 20

Vapour Density of a gas is the ratio between the mass of certain volume of
the gas & the mass of the same volume of hydrogen at the same temperature
and pressure.

Question 21

AVOGADRO NUMBER

Answer 21

one molecular mass (i.e. one mole) of every gas occupies 22.4
litres at S.T.P.
according to Avogadro’s hypothesis equal volumes of all gases at
S.T.P contain equal number of molecules.
Hence it follows that 1 mole of every gas contains the same number of
molecules. This number is called the Avogadro’s number or Avogadro’s
Constant. It is denoted by N. It has been found to be equal to 6.023 x 1023. It
can be defined as “the number of atoms or molecules present in one
mole of an element or a compound respectively”.

Question 22

Acids

Answer 22

An acid is a substance that gives hydrogen ions (H+
) by itself or in
aqueous solution.

Question 23

Bases

Answer 23

A base is a substance that gives ions (OH-
) by itself or in aqueous solution.

Question 24

THEORIES OF ACIDS AND BASES

Answer 24

By the following theories, the acidic and basic nature of substances can be
easily explained
1. Arrhenius theory
2.Lowry-Bronsted theory
3.Lewis theory.

Question 25

Arrhenius Theory (1827)

Answer 25

Arrhenius Theory (1827)
According to this theory, an acid is a substance that gives hydrogen (H+) ions in water or in aqueous solution.

HCl gives H+ in water, hence it is called as acid.
A Base is a substance that gives hydroxyl ions in water or in aqueous solution

NaOH gives OH– in water; hence, it is called as base.
Strength of an acid (or) base depends upon the extent to produce H+ (or) OH– during ionization.