Chapter 1 Chemistry 2012 FinL

8/2/2019 Chapter 1 Chemistry 2012 FinL

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Chemistry 9 Ch: 1 Fundamentals of Chemistry

Jadeed Dastgir Ideal High School0333-6623700

Book Short Questions

Q.1: What is Science?

Ans: Science is the classified knowledge of facts gained through observations, generalizations, correlationsand experimentations.

Q.2: Define Chemistry?

Ans: The branch of science which deals with the study of matter, its composition and structure, changes in

matter and laws and principles which govern these changes.

Q.3: Define Matter? Give examples?

Ans: Anything that has mass and occupies space is called matter. The examples of matter are air, gases,

solutions of salts, etc.

Q.4: Define Physical Chemistry?

Ans: It deals with the relationship between the composition and physical properties of matter along with

the changes in them. The properties such as structure of atom or formation of molecules, behavior of

gases, liquids and solids etc. are studied under this branch.

Q.5: Differentiate between Organic and Inorganic Chemistry?

Ans:Organic Chemistry: It is the study of covalent compounds of carbon and hydrogen (hydrocarbons)

and their derivatives.

Inorganic Chemistry: It is the study of all elements and their compounds except hydrocarbons and

their derivatives.

Q.6: Define Analytical Chemistry?

Ans: It deals with the separation and analysis of a sample to identify its components. The separation is

carried out prior to qualitative and quantitative analysis.

Q.7: Define Industrial Chemistry?

Ans: It is the branch of chemistry which is related to industrial processes. In other words, the study of

properties, uses and their techniques of preparation of industrial products on large scale are studied inindustrial chemistry.

Q.8: Define Environmental Chemistry?

Ans: It is the branch of chemistry which deals with the chemicals and other pollutants in the environment

resulting directly and indirectly from human activities.

Q.9: Define Nuclear Chemistry?

Ans: It is the branch of chemistry which deals with the radioactivity, nuclear processes and properties. The

main concern of this branch is with the energy of the atom and its uses in daily life.

Q.10: Define Bio-chemistry?

Fundamentals of Chemistry1 Fundamentals of Chemistry


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Ans: It deals with the study of structure, composition and chemical reactions of substances found in living

organisms.

Q.11: What is the modern definition of Element? Give examples?

Ans: Modern definition of element is that it is a substance made up of same type of atoms, having same

atomic number and it cannot be decomposed into simpler substance by chemical means.

Examples: hydrogen (H2), Iron (Fe), Copper (Cu) etc.

Q.12: Define Compound? Give examples?

Ans: The substance made up of two or more elements chemically combined together in fixed ratio by mass

Examples: hydrogen chloride (HCl), glucose (C6H12O6), etc.

Q.13: Define Mixture? Give examples?

Ans: When two or more elements or compounds mix-up physically without any fixed ratio, they form a

mixture. For example, Air, Ice cream, etc.

Q.14: How does homogeneous mixture differ from heterogeneous mixture?

Ans: Homogeneous Mixture: The mixture which is clearly uniform throughout and in which particles of

substances are evenly distributed into each other is called homogeneous mixture, e.g. air, ice cream.

Heterogeneous Mixture: The mixture which is not uniform at all in its composition is called

heterogeneous mixture, e.g. soil.

Q.15: Define Substance? Give examples?

Ans: A piece of matter in pure form is called as Substance. Every substance have fixed composition and

fixed properties.

All elements and compounds are substances.

For example, carbon, water and alcohol are pure substances.

Q.16: Differentiate between physical and chemical properties?

Ans: The properties which are associated with the physical state of matter are called physical properties,

like colour, taste smell etc.

The properties which are associated with composition of matter when a substance undergoes a

chemical change are called chemical properties.

Q.17: Define Atomic Number? Give examples?

Ans: The number of protons in the nucleus of an atom is called atomic number. It is represented by Z.

In a neutral atom;Atomic No. of an atom Z No of protons No of electrons

For example, Atomic No. of hydrogen = 1, because it has only one proton.

Q.18: Define Mass number? Give examples?

Ans: The total number of protons and neutrons in the nucleus of an atom is called mass number. It is also

called Nucleon number. It is represented by A.

In an neutral atom;

Mass Number = No. of Protons + No. of Neutrons

A = Z + N

For example, Mass number of hydrogen is 1, and for Oxygen is 16.


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Q.19: Define Atomic Mass Unit ( amu) ?

Ans: One atomic mass unit is of the mass of C12 atom. Its symbol is amu.

Q.20: Define Relative Atomic Mass?

Ans: The average mass of atoms of that element as compared to of the mass of C-12atom is known

as relative atomic mass. Its unit is amu.

Q.21: Define Chemical Formula?

Ans: A representation of the composition of a substance (element or molecule) using symbols is called

Chemical Formula. OR

The shorthand notation of a compound is called a Chemical Formula.

For example Chemical formula of water is H2O.

Q.22: Define Molecular Formula?

Ans: The formula which represents the actual number of atoms of each element present in one molecule

of the substance is called Molecular Formula.

For example, Molecular Formula of water is H2O.

Q.23: Define Empirical Formula?

Ans: The formula which shows the simplest whole number ratio between atoms of each element present

in one molecule of a substance is called Empirical Formula.

For example, the molecular formula of Benzene is (C6H6) but its empirical formula is (CH).

Q.24: What is the relation between Molecular Formula and Empirical Formula?

Ans: The molecular formula and empirical formula are related as follows:

Molecular Formula = ( Empirical Formula )nWhere n is 1,2,3 and so on.

Q.25: Define Molecule? Give examples?

Ans: A molecule is the smallest particle of a covalent compound or an element which has an independent

existence. A molecule may consist of a single or more atoms.

Examples:( H2 ) is the molecule of hydrogen, ( H2O ) is the molecule of water.

Q.26: What is Formula Unit?

Ans: The formula which shows the minimum (simplest) ratio between the ions of the ionic compound is

called Formula Unit. For example Formula of Sodium Chloride is NaCl, which shows the simplest

ratio between the ions of sodium (Na+) and chloride (Cl) ions.

Q.27: Define Molecular Mass?

Ans: The sum of atomic masses of all the atoms present in one molecule of a molecular compound is

called its molecular mass. It unit is amu.

We can find No. of neutrons, if we subtract Z (Atomic number) from A (Mass number).

N = A -- Z


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Q.28: What is Formula Mass?

Ans: The sum of the atomic mass of all the atoms present in the one formula unit of a substance is called

Formula Mass.

Ionic Compounds and network covalent compounds have formula units, so we use Formula Mass

for these compounds. Such as Silica (SiO2) , Sodium Chloride (NaCl). It has formula mass 58.8

amu.

Q.29: Define homoatomic molecule?

Ans: A molecule consists of same type of atoms is called homoatomicmolecule.

Examples are H2, S8, Cl2

Q.30: Define hetroatomic molecule?

Ans: A molecule consists of different types of atoms is called hetroatomic molecule.

Examples: H2O, CO2

Q.31: Define monoatomic molecule?

Ans: A molecule consists of only one atom is called monoatomic molecule.

Examples: Inert gases, i.e. Helium (He), neon (Ne).

Q.32: Define diatomic molecule?

Ans: A molecule consists of two atoms is called diatomic molecule.

Examples: H2, N2, HCl

Q.33: Define triatomic molecule?

Ans: a molecule consists of three atoms is called triatomic molecule.

Examples:CO2, H2O

Q.34: Define Cation or Positive Ion?Ans: An atom or group of atoms having positive charge on it is called Cation. When an atom loses

electron it forms cation.

oA A 1e

neutral atom Cation

e.g. Na+, Ca

2+, Al

3+

Q.35: Define Anion or Negative Ion?Ans: An atom or group of atoms having negative charge on it is called Anion. When an atom gains

electron it forms anion.

oA 1e A

neutral atom Anion

e.g. O2, S

2, Cl

1

Q.36: What is Valency?

Ans: It is combining capacity of an element with the other elements. It depends upon the number of

electrons in the outermost shell. e.g. Sodium has one valance electron so its valency is 1.

Q.37: What is molecular Ion?

Ans: A molecule having positive or negative charge is called Molecular ion. It is also called a radical.When molecule loses or gains an electron it forms molecular ion. e.g. NH4

+, NO3

1.

Q.38: Define Free Radical?


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Ans: Atoms or group of atoms possessing an odd (unpaired) electron. It is represented by putting a dot

over the symbol of an element.

Examples: Methyl free radical3CH

, Chlorine free radicalCl

.

Q.39: Define Avogadros number? Or how mole is related to Avogadros number?

Ans; The number of atoms, molecules, ions or formula units in an element, compound in one mole of

substance is called Avogadros number. Its value is 6.02 1023. It is denoted by NAe.g

One mole ofO2molecule = 32g = 6.02 1023 molecules

One mole of NaCl formula unit = 58.5 g = 6.02 1023formula units

Q.40: Define Mole?

Ans: Mole is the amount (mass) of a substance that contains 6.02 1023

number of particles (atoms,

ions, molecules or formula units).

e.g

One mole ofO2molecule = 32g = 6.02 1023 molecules

One mole of NaCl formula unit = 58.5 g = 6.02 1023

formula units

Q.41: How many particles are there in one mole of a substance?

Ans: 6.02 1023

particles.

Q.42 Define Gram Atomic Mass?

Ans: The atomic mass of an element expressed in grams is called gram atomic mass orgram atom. It is

also called a mole.

e.g. 1 gram atom of hydrogen (H) = 1.008 grams = 1 mole of hydrogen

Q.43 What is Gram Molecular Mass?

Ans: The molecular mass of a molecular substance expressed in grams is known as gram molecular

mass orgram molecule. It is also called a mole.

e.g. 1 gram molecule of water (H2O) = 18.0 grams = 1 mole of water molecule.

Q.44 What is Gram Formula mass?

Ans: The formula mass of an ionic compound is expressed in grams is known as gram formula mass or

gram formula of substance. It is also called a mole.

e.g 1 gram formula of NaCl = 58.8 grams = 1 mole ofNaCl formula unit.

Exercise Short Questions

Q.1: Define Industrial and Analytical Chemistry?

Ans: Industrial Chemistry: The branch of chemistry that deals with the manufacturing of chemical

compounds on commercial scale.

Analytical Chemistry: It deals with the separation and analysis of sample to identify its components.

Q.2: Differentiate between Organic and Inorganic Chemistry?


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Formulas to Remember

mole-mass calculations

no. of moles = known mass

molar mass

mole- particle calculations

no. of moles = numberof particles

AN

Q.11: Classify the following into elements, compound and mixture:

(i) He and H2 (ii) CO and Co (iii) Water and Milk (iv) Gold and Brass (v) Iron and Steel

Ans: (i) He is an element and H2is a compound.

(ii) CO is a compound and Co is an element.

(iii) Water is a compound and Milkis a mixture.

(iv) Gold is an element and Brass is a mixture.

(v) Iron is an element and Steel is a mixture.

Q.12: Define Atomic Mass Unit (amu)? Why is it needed?

Ans: The mass equal to of the mass of C12 atom is called Atomic Mass Unit. Its symbol is

amu.

Atom is very tiny particle and at this level, gram is not suitable. There was a need of a separate unit

for this purpose, so amu was formulated.

Q.13: State the nature and name of the substance formed by combining the following?i. Zinc + Copper ii. Water + Sugar iii. Aluminum + Sulphur iv. Iron+Chromium+nickel

Ans: i. zinc + copper Brass (mixture)

ii. water + sugar Sugar solution (mixture)

iii. Aluminum + Sulphur Aluminum Sulphate (compound)

iv. Iron + Chromium + Nickel Nichrome (mixture)

Q.14: Differentiate between molecular mass and formula mass, which of the following will be

molecular formula?

H2O , NaCl , KI , H2SO4

Ans: The sum of atomic masses of all the atoms present in one molecule of a molecular compound is

called its molecular mass.

H2O and H2SO4have molecular mass.The sum of the atomic mass of all the atoms present in the one formula unit of a substance is called

formula mass.

NaCl and KI have formula mass because these are ionic compounds.

Q.15: Which one has more atoms: 10 g of Al or 10 g of Fe?

Ans: 10 g ofAl has more atoms than 10g ofFe.10 g of Al has moles =

10

27= 0.37 mol

10 g of Fe has moles =

10

56 = 0.17 mol

Now, no. of atoms = no. of moles NA

no. of atoms in Al = 0.37 6.02 1023 = 2.22 1023 atoms

no. of atoms in Fe = 0.178 6.021023 = 1.07 1023 atom

Q.16: Which one has more molecules: 9 gram of water or 9 g of sugar (C11H22O11)?

Ans: 9 g ofwater has more molecule than 9 g ofsuger.

9 g of water has moles =9

18= 0.5 mol

9 g of suger has moles =9

342= 0.0263 mol

Now, no. of molecules = no. of moles NA


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RememberThe term Molecule is always used forcovalent compounds and term Formulaunit is used

forIonic compounds.

The term Molecular mass is always used forcovalent compound and term Formulamassis used forIonic compounds.

no. of molecules in water = 0.5 6.02 1023 = 3.011023 molecules

no. of moleucles in suger = 0.0263 6.02 1023 = 0.1581023 = 1.581022 molecules

Q.17: Which one has more formula units: 1 g of NaCl of 1g of KCl?

Ans: 1 g ofNaCl has more formula units than 1g ofKCl.

1 g of NaCl has moles =1

58.5

= 0.017 mol

1 g of KCl has moles =1

74.5= 0.0134 mol

Now, no. of formula units = no. of moles NA

no. of formula units in NaCl = 0.017 6.02 1023 = 0.1021023 = 1.021022 formula units

no. of formula units in KCl = 0.0134 6.02 1023 = 0.0801023 = 0.081022 formula units

Q.18: Differentiate between homoatomic and heteroatomic molecules with examples?

Ans: A molecule consists of same type of atoms is called homoatomicmolecule.Examples: H2, S8, Cl2A molecule consists of different types of atoms is called hetroatomic molecule.

Examples: H2O, CO2

Q.19: In which of the following cases the number of hydrogen atoms is more: 2 moles of HCl or 1

mole of NH3 ?

Ans: 1 mole ofNH3 contains more number of hydrogen atoms than 2 moles ofHCl.

2 moles ofHCl has moles of hydrogen = 2 moles

1 moles ofNH3 has moles of hydrogen = 3 moles

Now, no. of atoms = no. of moles NA

number of atoms of hydrogen in HCl = 2 6.02 1023 = 12.041023 = 1.20 1024 atoms

number of atoms of hydrogen in NH3 = 3 6.02 1023 = 18.061023 = 1.801024 atoms

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Chapter 1 Chemistry 2012 FinL