Download chemistry (chapter 1)

CHEMISTRY
SHORT QUESTIONS
CHAPTER # 1
1) Define Science.
The knowledge that provides understanding of this world and how it works is called science.
2) Define chemistry.
The branch of science which deals with the composition, structure, properties and reaction of
matter is called chemistry.
3) How development of science facilitate our daily life.
The development of science has provided us a lot of facilities in daily life. Imagine the
importance of petrochemical products, medicines and drugs, soap, detergents, paper plastic
paints and pigments, insecticides and pesticides.
4) What are disadvantages of development of science.
The development of chemical industry has also generated toxic wastes, contaminated water
and polluted air around us.
5) In How many branches Chemistry is divided.
Chemistry is divided in following main branches
i) physical chemistry
ii) organic chemistry iii) inorganic chemistry
iv) analytical chemistry v) industrial chemistry vi) nuclear chemistry
vii) environmental chemistry
viii) biochemistry
6) Define Physical Chemistry.
The branch of chemistry that deals with the relationship between the composition and
physical properties of matter along with the changes in them.
7) Define Organic Chemistry.
The study of covalent compounds of carbon and hydrogen (hydrocarbons) and their
derivatives.
8) Define Inorganic Chemistry.
The study of all elements and compounds except those of compounds of carbon and
hydrogen (hydro carbons) and their derivatives.
9) Define Biochemistry.
The branch of chemistry in which we study the structure , composition and chemical
reactions of substance found in living organisms.
10) Define Industrial Chemistry.
The branch of chemistry that deals with the manufacturing of chemical compounds on
commercial scale.
11) Define Nuclear Chemistry.
The branch of chemistry that deals with the radioactivity nuclear processes and properties.
12) Define Environmental Chemistry.
The branch of chemistry in which we study about components of the environment and the
effect of human activities on the environment.
13) Define Analytical Chemistry.
The branch of chemistry that deals with separation and analysis of a sample to identify its
components.
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CHEMISTRY
SHORT QUESTIONS
CHAPTER # 1
14) Define Matter, Substance and Mixture.
Matter: Anything that has mass and occupies space.
Substance: A piece of matter in pure form is known as substance
Mixture: When two or more elements or compounds are mix-up physically without any
fixed ratio they form a mixture.
15) Define Physical properties.
The properties that are associated with the physical state of matter are called physical
properties like color, smell, taste, hardness, shape of crystal, solubility, melting or boiling
point.
16) Define Chemical properties.
The chemical properties depend on the composition of the substance. When a substance
undergoes a chemical change, its composition changes and new substances are formed. For
example decomposition of water is a chemical change
17) Write modern definition of element.
It is a substance made up of same type of atoms having same atomic number and it cannot be
decomposed into simple substances by ordinary chemical means
Now 118 elements have been discovered out of which 92 are naturally occurring elements.
18) How many physical forms of elements have?
Elements may be solid, liquid or gasses. Majority of the elements are solids e.g copper, zinc,
gold etc. there are very few elements which occur in liquid state e.g mercury and bromine. A
few elements exist as gasses e.g nitrogen, oxygen, chlorine and hydrogen.
19) Classify elements on the bases of their properties.
On the basis of properties elements are divided into metal, non-metals and metalloids. About
80 percent of the elements are metals.
20) What is symbol?
The elements are represented by symbols. Symbols are the abbreviations for the name of
elements.
21) Define valency.
The unique property of an element is valency. It is combining capacity of an element with
other elements.
22) What is compound?
Compound is a substance made up of two or more elements chemically combined together in
a fixed ratio by mass.
Example: Water is a compound formed by a chemical combination between hydrogen and
oxygen in a fixed ratio of 1:8 by mass.
23) In how any types compounds can be classified?
Compounds can be classified in to two types
1) Ionic compounds
2) Covalent compound
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CHEMISTRY
SHORT QUESTIONS
CHAPTER # 1
24) Define Ionic compounds.
Ionic compounds cannot exist in independent molecular form. They form a three dimensional
crystal lattice, in which each ion is surrounded by oppositely charge ions. They have high
melting and boiling point. These compounds are represented by formula units e.g.NaCl ,KBr,
CuSO4
25) Define covalent Compounds.
Covalent compound exist in molecular form. A molecule is a true representative of the
covalent compound and its formula is called Molecular formula e.g H2O. HCl, H2SO4, CH4
26) How a mixture can be separated into parent component.
The mixture can be separated into parent component by physical method such as distillation,
filtration, evaporation, crystallization or magnetization.
27) In How any types Mixtures are classified.
Mixtures are classified as
i) Homogeneous mixture: Mixtures that have uniform composition throughout e.g air,
gasoline, ice-cream
ii) Heterogeneous mixtures: Mixture in which composition is not uniform throughout e.g
soil, rock and wood.
28) Define Atomic number and Mass number.
Atomic number: The atomic number of an element is equal to the number of protons
present in the nucleus of its atoms. It is represented by symbol “Z”.
Mass number: The mass number is the number of protons and neutrons present in the
nucleus of an atom. It is represented by Symbol “A”
Example: Atomic number of carbon is 6 and mass number of carbon is 12.
29) Define relative atomic mass and atomic mass unit.
Relative atomic mass: The relative atomic mass of an element is the average mass of an
atoms of the element as compared to 1/12th the mass of an atom of carbon-12 isotope.
Atomic mass unit: The unit for relative atomic masses is called atomic mass unit, with
symbol “amu”. One atomic mass unit is 1/12th the mass of one atom of carbon-12th
1 amu = 1.66 x 10-24 g
30) How many types of chemical formula has?
Chemical formula are of two types
1) Empirical formula
2) Molecular formula
Empirical formula: The simplest whole number ratio of atoms present in a compound.
Example: Empirical formula of silica (sand) is SiO2 which has simplest ratio of 1:2 of
silicon and oxygen.
Molecular formula: molecular formula shows actual number of atoms of each element
present in a molecule of a substance.
Example: molecular formula of water and sulfuric acid is H2O and H2SO4 respectively.
Molecular formula = (Empirical Formula) x n
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CHEMISTRY
SHORT QUESTIONS
CHAPTER # 1
31) Define formula unit.
The simplest whole number ratio of oppositely charged ions that gives an electrically neutral unit
of an ionic compound is called formula unit.
Example: In Sodium chloride (NaCl) the ratio of Na+ ions to the Cl- ions is 1:1.
32) Define molecular mass.
The sum of atomic masses of all the atoms present in one molecule of a molecular compound is
called molecular mass.
Example:
Molecular mass of H2O = (1x2)+(16) = 18 amu
33) Define formula mass.
The sum of atomic masses of all the atoms present in one formula unit of an ionic compound is
called formula mass.
Example:
Formula mass of NaCl = 23 + 35.5 = 58.5 amu
34) Define chemical specie and Ion.
Chemical specie: The atoms, molecule, molecular ion, and free radical are called chemical
specie e.g Na, H20, Na+
Ion: An atom or group of atoms having a charge on it is called ion. There are two types of ions
i) Cation
ii) Anion.
e.g Na+, Cl35) Define Cation and Anion.
Cation: An atom or group of atoms having positive charge on it is called cation. e.g K+, Na+,
Mg2+
Anion: An atom or group of atoms having negative charge on it is called anion. e.g Cl--, O2--,
Br36) Define Monoatomic and Polyatomic ion.
Monoatomic Ion: An ion having a single atom is called monoatomic ion. e.g H--, Cl--, H+,
Na+
Polyatomic Ion: An ion having two or more atoms is called polyatomic ion. e.g NH4+, OH--,
NO4--.
37) Differentiate between atom and ion.
Atom
Ion
i) It is the smallest particle of an element
i) It is the smallest unit of an ionic compound
ii) it may or may not have independent
ii) It cannot exist independently. Existence
ii) It is electrically neutral
iii) It carries an electric charge positive or
negative.
38) Define molecular ion.
When a molecule losses or gain electron, it forms a molecular Ion.
Examples: N2+, H2+, CH4+
cationic molecular ions are more abundant than anionic molecular ion.
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CHEMISTRY
SHORT QUESTIONS
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39) Write differences between Molecule and Molecular ion.
Molecule
Molecular Ion
i) It is the smallest particle of an element or
i) It is formed by gain or loss of electrons
by a compound which can exist independently
molecule.
and shows all the properties of that compound
ii) It is always neutral
ii) It can have negative or positive charge
iii) It is formed by combination of atom
iii) It is formed by ionization of a molecule.
iv) It is a stable unit
iv) It is reactive specie.
40) Define free radical.
Free radical are atoms or group of atoms possessing odd number of (unpaired) electrons. It is
represented by putting a dot over the symbol of an element. e.g H”, Cl”, H3C”
41) Differentiate between ions and free radicals.
Ions
Free radicals
i) These are atoms or group of atoms having
i) These are atoms or group of atoms
charge
having odd electrons.
ii) They exist in solution or in crystal lattice
ii) They exist in solution as well as in air.
iii) Their formation is not affected by the
iii) They may form in the presence of
presence of light.
light
42) Define Atom.
The smallest particle of an element which can take part in a chemical reaction is called Atom.
An atom may or may not have independent existence.
Example: He, Ne exist independently while O, H, N, Na etc do not have independent
existence.
43) Define Molecule.
The smallest particle of a substance which can exist independently and shows all the
properties of the substance is called molecule.
Example: H2, O2, O3, HCl etc
44) Describe different types of molecules depending upon the number of combining
atoms.
There are different types of molecules depending upon the number of combining atoms
which are given below.
i) Monoatomic Molecule: A molecule consisting of only one atom of element is called
monoatomic molecule. e.g all noble gasses like He, Ne, Ar, Kr, Xe
ii) Diatomic Molecules: A molecule consisting of two atoms is called a diatomic molecule.
e.g H2, N2, HCl
iii) Triatomic Molecules: A molecule consisting of three atoms is called a triatomic
molecule. e.g CO2, H2O, NO2
iv) Polyatomic Molecule: A molecule consisting of many atoms is called polyatomic
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CHEMISTRY
SHORT QUESTIONS
CHAPTER # 1
molecule. e.g CH4, NH3,
45) Describe different types of molecules depending upon the type of combining
atoms.
There are different types of molecules depending upon the type of combining atoms which
are given below.
i) Homoatomic Molecule: A molecule of an element containing same type of atoms is
called homo atomic molecule. e.g H2, N2, O2 etc.
ii) Heteroatomic Molecule: A molecule of a compound containing different kinds of
atoms is called a heteroatomic molecule. e.g H2O, NO2 , CH4 etc
46) Define gram atomic mass.
The atomic mass of an element expressed in grams is called gram atomic mass.
1 gram atom of Hydrogen = 1 mole of Hydrogen = 1.008 g
1 gram atom of Oxygen = 1 mole of Oxygen = 16.0 g
47) Define gram Molecular mass.
The molecular mass of a substance expressed in grams is called gram molecular mass
1 gram molecule of water = 1 mole of water = 18.0 g
1 gram molecule of sulfuric acid = 1 mole of sulfuric acid = 98.0 g
48) Define gram formula mass.
The formula mass of an ionic compound expressed in grams is called gram formula mass.
1 gram formula of NaCl = 1 mole of NaCl = 58.5 g
1 gram formula of CaCO3 = 1 mole of CaCO3 = 100
49) Define Avogadro’s Number.
The number 6.02 x 1023 of particles of any kind ( atoms, ions, molecules or formula units ) in
one mole of a substance is called Avogadro’s number. It is represented by Symbol NA .
1 Mole = 6.02 x 1023 particles
Examples:
1 mol of O = 6.02 x 1023 atoms of O.
1 mol of C = 6.02 x 1023 atoms of C.
50) Define Mole.
The amount (mass) of a substance that contains 6.02 x 1023 particles (atoms, ions, molecules
or formula units) is called a mole. When it is used as a unit it is abbreviated as mol.
Examples:
1 mol of C = atomic mass of C = 12.0 g
1 mol of NaCl = formula mass of NaCl = 58.5 g
Relationship between mol and mass:
Number of moles of a substance =
Mass of a substance
Molar mass of a substance
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CHEMISTRY
SHORT QUESTIONS
CHAPTER # 1
Exercise Short Questions
1) Define Industrial Chemistry and Analytical Chemistry.
Industrial Chemistry: The branch of chemistry that deals with the manufacturing of
chemical compounds on commercial scale.
Analytical Chemistry: The branch of chemistry that deals with separation and analysis of a
sample to identify its components.
2) How can you differentiate between Organic and Inorganic Chemistry?
Organic Chemistry: The study of covalent compounds of carbon and hydrogen
(hydrocarbons) and their derivatives.
Inorganic Chemistry: The study of all elements and compounds except those of
compounds of carbon and hydrogen (hydro carbons) and their derivatives.
3) Give the scope of Biochemistry.
Biochemistry is the chemistry of life. The knowledge of biochemistry is essential to all life
sciences. It deals with al chemical processes taking place in living organisms. It is applied in
the field of medicine, food science, agriculture, and our natural environment.
4) How does Homogeneous mixture differ with Heterogeneous mixtures?
Homogeneous mixture: Mixtures that have uniform composition throughout e.g air,
gasoline, ice-cream
Heterogeneous mixtures: Mixture in which composition is not uniform throughout e.g
soil, rock and wood.
5) What is relative atomic mass? How it is related to gram?
The relative atomic mass of an element is the average mass of an atoms of the element as
compared to 1/12th the mass of an atom of carbon-12 isotope.
1 amu = 1.66 x 10-24 g
6) Define Empirical formula with example.
Empirical formula: The simplest whole number ratio of atoms present in a compound.
Example: Empirical formula of silica (sand) is SiO2 which has simplest ratio of 1:2 of
silicon and oxygen.
7) State three reasons why do you think air is a mixture and water is a compound.
i) Air does not have any chemical formula whereas water a chemical formula H2O.
ii) Air is formed by simple mixing of N2, O2, CO2 and noble gasses whereas water is formed
by chemical combination of H2 and O2 .
iii) Air does not have any fixed melting point whereas water has a fixed melting point .
8) Explain why Hydrogen and oxygen considered elements and water is a
compound.
i) Both Hydrogen and Oxygen cannot be chemically broken down into simpler substances
Whereas Water can be chemically broken down into hydrogen and oxygen.
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CHEMISTRY
SHORT QUESTIONS
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ii) Both hydrogen and Oxygen are identified by symbols whereas water is identified by a
chemical formula.
9) What is significance of symbol of an element?
i) A symbol is short hand representation of element.
ii) A symbol may be used in place of the name of an element. iii) A symbol may be used to
refer to the element in general.
10) State the reason: soft drink is a mixture and water is a compound.
i) soft drink is a mixture. It is formed by mixing physically two or more compounds without
any fixed ratio. Water is a compound. It is formed by chemical combination of two elements
hydrogen and oxygen in a fixed ratio of 1:8 by mass.
ii) The compounds of soft drink retain their chemical identities and properties whereas the
components of water hydrogen and oxygen lost their properties.
11) Classify following into elements, compounds and mixture:
i) He and H2 are elements
ii) CO is a compound and Co is an element
iii) Water is a compound and milk is a mixture
iv) Gold is element and Brass is a mixture
v) Iron is an element and Steel is a mixture.
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