Chemistry For Class IX (New Book ) - Chapter No. 1- Fundamentals of Chemistry - Long Questions And Answers

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Chapter No.1 - Fundamentals of Chemistry
Long Questions And Answers
Text Book Exercise

SECTION- C: DETAILED QUESTIONS:

1. What do you mean chemical species, explain ion, molecular ion and free radical? OR Classify the chemical species from the given examples.
Ans: CHEMICAL SPECIES:
If one molecule is identical to another we can say they are the same chemical species. Chemical species is a chemical entity, such as particular atom, ion or molecule.

IONS:
Ion is an atom or group of atoms having a charge on it. The charge may be positive or negative.

TYPES OF IONS:
There are two types of ions:

• Cations and
• Anions

Cations:
The cations are formed when an atom loses electrons form its outer most shells.
For example: Na⁺ , K⁺ are cations.
Formation of cations:
The following equation shows formation of cations.

Na ⟶ Na⁺ + 1e^-

Anion:
An atom or group of atom that has a negative charge on it is called anion.
For example: Cl^- and O^2- are anions.
Formation of anions:
Anion is formed by the gain or addition of electrons to an atom. Following examples shows formation of an anion by addition of electrons to an atom.

Cl + 1e^- ⟶ Cl^-

MOLECULAR IONS:
When a molecule loses or gains electrons called molecular ions. Molecular ions also possess positive or negative charge like any ion.

TYPES OF MOLECULAR IONS:
There are two types of molecular ions

• Anionic molecular ions
• Cationic molecular ions

Anionic molecular ions:
If it has negative charge known as anionic molecular ions.
For example: SO₄^2-.

Cationic molecular ions:
If they has positive charge known as cationic molecular ions.
For example: NH₄⁺

FREE RADICALS:
Free radicals are atoms and group of atoms having number of unpaired electrons. It is represented by putting a dot over the symbol of an element.
For example: H^° , Cl^° ,H₃^°, C^°
Formation Of Free Radicals:
Free radicals are formed when homolytic breakage of bond between two atoms takes place by the absorption of heat or light energy. Free radical is very reactive chemical species.

2. Writ down the applications of chemistry in daily life? OR Write down the importance of chemistry in daily life.
Ans: Applications OR Importance Of Chemistry In Daily Life:
The role of chemistry in daily life is unavoidable fact, It plays important role:

1. In Our Food:
Cooking, eating and digestion of food are purely chemical processes.

2. In our Home:
Construction, cleaning and washing of our homes are dependable on chemistry.

3. Productions Of chemicals:
The production of fertilizers, glass, plastic synthetic fiber, polymer, ceramics, petroleum products, soaps, and detergents are based on chemistry.

4. Over come On Diseases:
Our planet earth has only life in the all planet of universe, due to existence of water (H₂O). The water is basic need of human, animals and plants. The chemical reactions take place in human, animals and plants. Disorder in these reactions may cause different diseases. Which may be over come with the help of chemistry.

5. Kill Pathogenic organisms
The diseases transmitted through impure drinking water as cholera, typhoid, dysentery, skin and eye infections can be controlled with the help of chlorine treatment to kill the pathogenic organism to obtain pure water.

6. In Industries:
The chlorine is most important chemical which used commercially to produce more than one thousands compounds which are used in chemical industry as bleaching agent, disinfectants, solvents, pesticides, refrigerates, PVC and drugs are miracles of chemistry.

3. Define chemical formula? Explain in detail empirical and molecular formula?
Ans: CHEMICAL FORMULA:
The compounds are represented by Chemical Formula as elements are represented by symbols with respect to valencies.

OR

The chemical formula represent the symbol of elements and ratios of elements to one another in a compound.

OR

Chemical formula tells us number of atoms of each element in a compound with symbols.
For Example:

1. Chemical formula of water is H₂O which indicates that 2 atoms of hydrogen combines with 1 atom of oxygen.
2. Chemical formula of ammonia NH₃ shows that one nitrogen atom combines with 3 atoms of hydrogen.

TYPES OF CHEMICAL FORMULA:
Chemical formula are of two types:

• Empirical Formula and
• Molecular Formula.

EMPIRICAL FORMULA:
The formula showing minimum relative numbers of each type of atoms in a molecule is called Empirical Formula.

• Empirical Formula shows simplest ratio of each atoms present in a molecule.
• Empirical Formula does not show the actual number of atoms in the molecule.
• Empirical Formula tells us the type of element present in it.

For Example:
( 1) Benzene has molecular formula C₆H₆ . Which has simplest ratio f hydrogen and carbon is 1:1, so the empirical formula becomes CH.
(2) Glucose has molecular formula C₆H₁₂O₆. It shows the ratio as follows:

C₆H₁₂O₆

6:12:6

1:2:1

C : H₂ : O

So the empirical formula of glucose is CHO and have simple ratio 1:2:1 of atoms in molecule of glucose.

MOLECULAR FORMULA:
The Molecular formula is the formula which shows actual number of atoms of each element present in a molecule.

• Molecular formula is derived from empirical formula.
• Molecular formula Mass calculated by adding atomic weights of its atoms.
• Molecular formula of a compound may be same or multiple of empirical formula.

For Example:
Molecular Formula of benzene is C₆H₆ , which have six carbon and six Hydrogen.
Formula Expression:
Molecular formula is an integral multiple (1,2,3 etc.) of the empirical formula.

Molecular Formula = (Empirical Formula)_n, where n=1, 2, 3, etc.

Some Compounds with their Empirical and Molecular Formula

Compound	Empirical Formula	Molecular Formula
Carbon dioxide	CO2	CO2
Glucose	CH2O	C6H12O6
Hydrogen peroxide	HO	H2O2
Benzene	CH	C6H6
Acetic Acid	CH2O	CH3COOH (C2H4O2)

4. (a) Define and explain chemical equation?
(b) Explain the steps for balancing the equation?
Ans: (a) CHEMICAL EQUATION:
Chemical equation is short hand method of describing the chemical reaction in terms of symbols and formulae of substances.

PARTS OF CHEMICAL EQUATION:

1. Reactant:
   The starting substances are known as reactants and always written on the left hand side of arrow.
2. Products:
   The substances are formed due to reactions of reactants are known as products and written on the right side of arrow.
3.  Arrow: 
   The reactants and products are separated from one another by using (⟶) single arrow or (⇋) double arrow depending type of reaction.
4. Coefficient:
   The number written in front of formula is called coefficient which shows number of molecules of that reactant or product.
5. State Of substance:
   The expression (s),(g) and(l) shows the state, solid ,gaseous and liquid of reactants and products. The expression (aq) express that substance is in the form of solution.
6. Catalyst:
   Similarly if catalyst is used this catalyst shown over the arrow.

For example:
When two molecules of hydrogen and one molecule of oxygen react two molecules of water formed instead of writing the full names of reactants and products, chemists show this reaction as follows in form of equation.

BALANCING CHEMICAL EQUATION
The chemical equation must be balance in order to fulfill Law of conservation of mass. Mostly chemical equations can be balanced by inspection method (trial and error method). We can balance the equation by following steps.

1. Write the correct formula of all reactants on the left side and products on the Right side of an arrow.
2. Balance the number of atoms on each side.
3. If the number of atoms may appears more or less than other side, balance the equation by inspection method. Multiply the co-efficient with formula to make the number of atoms same on the both (reactants and products) sides of equation.
4. The covalent molecules of hydrogen, nitrogen and chlorine exist as diatomic molecules. e.g H_2,  O₂, N₂ and Cl₂ . We must write them as diatomic molecule rather than isolated atoms in chemical equation.
5. Finally check the equation to be sure that number and kind of atom are same on the reactant and product side. If yes now equation is balanced.

For Example:
Let us consider, in laboratory oxygen (O ) gas is prepared by heating potassium chlorate (KCIO₃ ). The products are potassium chloride (KCI) and oxygen (O₂ ) gas.

Now balance the equation step wise.
Step no.1:
Write correct formula of all reactants on left side and product on right side of an equation.

KCIO_{3 (s)} ⟶ KCI_(s) + O_{2 (g)}

Step no.2:
Balance the number of atoms on each side.

Reactants	Products
K (1)	K (1)
Cl (1)	Cl (1)
O (3)	O (2)

We see that K and Cl elements have same number of atoms on both sides of equation but O is not balance because three atoms on reactant side and two atoms on product side.

Step no.3:
Now multiply the formula (KCIO₃) with co-efficient 2 on reactant side and 3 in front of oxygen on product side to balance the oxygen atoms.

2KCIO3 (s) Reactants	KCl(s) + 3O2 (g) Products
K (2)	K (1)
Cl (2)	Cl (1)
O (6)	O (6)

Step no.4:
Now again check and balance the equation by placing 2 in front of KCI on product side.

2KCIO_{3 (s)} ⟶ 2KCl_(s) + 3O_{2 (g)}

2KCIO3 (s) Reactants	KCl(s) + 3O2 (g) Products
K (2)	K (2)
Cl (2)	Cl (2)
O (6)	O (6)

Now this chemical equation is balanced.

5. Define Chemistry? Name the branches of chemistry and discuss any five branches? OR Differentiate between main branches of chemistry.
Ans: Definition of Chemistry:
Chemistry is the branch of science which deals with the properties, composition and structure of matter. Chemistry also deals with the changes involved in the matter.

BRANCHES OF CHEMISTRY:
Due to its wide scope Chemistry is divided in following main branches.

1. Physical Chemistry
2. Organic Chemistry
3. Inorganic Chemistry
4. Biochemistry
5. Industrial Chemistry
6. Nuclear Chemistry
7. Environmental Chemistry
8. Analytical Chemistry
9. Medicinal Chemistry
10. Quantum Chemistry
11. Green Chemistry

1. Physical Chemistry:
Physical chemistry is the branch of chemistry which deals with relationship between composition and physical properties of matter with the changes in them. It deals with the laws and principles governing the combination of atoms and molecules in chemical reactions.

2. Organic Chemistry:
Organic chemistry is the branch of chemistry which deals with hydrocarbons and their derivatives. Organic chemistry is the study of structure, properties, composition, reactions, and preparation of carbon-containing compounds, which include hydrocarbons except oxides, carbonates, bicarbonates and cynites. The gasoline, plastics, detergents, dyes, food additives, natural gas, and medicines are studied in the organic chemistry.

3. Inorganic Chemistry:
Inorganic chemistry is the branch of Chemistry which deals with the study of all elements and their compound except hydrocarbons. These compounds are generally obtained from nonliving organisms. It is applicable in all areas of chemical industry. Such as glass, cement, ceramics and metallurgy.

4. Biochemistry:
Biochemistry is the branch of Chemistry which deals with the compounds of living organisms. plants and animals and their metabolism and synthesis in the living body such as carbohydrates, proteins and fats. Biochemistry helps us to understand how living things obtain energy from food. It tells that how disorder or deficiency of these biomolecules causes diseases. This branch is useful in medicine, agriculture and food science.

5. Industrial Chemistry:
The branch of Chemistry which deals with the study of chemical processes involved in the chemical industries for the manufacture of synthetic products like fertilizers, glass, cement and medicines is called as industrial chemistry.

6 Nuclear Chemistry:
Nuclear chemistry is the branch of Chemistry which deals with the radioactivity, nuclear processes and properties. Radioactive elements are widely used in medicine as diagnostic tools and as a means of treatment, especially for cancer, preservation of food and generation of electric power through nuclear power reactors.

7. Environmental Chemistry:
It is the branch of Chemistry which deals with the study of the interaction of chemical materials and their effect on the environment of animals and plants. Personal hygiene, pollution, health hazards are the important areas of environmental chemistry.

8. Analytical Chemistry:
Analytical chemistry is the branch of chemistry which deals with separation and analysis of kind, quality and quantity of various components in given substance, It used in chromatography, electrophoresis and spectroscopy.

9. Medicinal Chemistry:
The branch of Chemistry which deals with synthetic organic chemistry, pharmacology and various biological specialties. The medicinal chemistry is used in synthesis of chemicals, bioactive molecules (Drugs) and pharmaceutical agents.

10. Quantum Chemistry:
The branch of Chemistry which deals with application, mechanics and experiments of physical models in chemical system. It is also called molecular quantum mechanics.

11. Green Chemistry:
The branch of chemistry which deals with study of processes and designing products, which are composed of less hazardous substances. It is also known as sustainable chemistry.

Long Questions And Answers

Q.6: Write down the historical background of chemistry. Or Explain the contribution of Muslim and non Muslims scientists in the development of chemistry.
Ans: Historical background of chemistry

Contribution Of Muslim Scientists

1. Jabir Ibne-Haiyan (721 - 803 A.D) Muslim scientist:
Contribution:

• Invented experimental methods of nitric acid, hydrochloric acid and white lead.
• Extraction of metals from their ores and dyeing clothes.

2. Al-Razi (862-930 A.D) Muslim scientist:
Contribution:

• Prepared ethyl alcohol by fermentation process.

3. Al-Beruni (973-1048 A.D) Muslim scientist:
Contribution:

• Determined densities of different substances.

4. Ibne –Sina (980-1037 A.D) Muslim scientist:
Contribution:

• Contributed in medicines, philosophy and astronomy.

Contribution Of Non Muslims Scientists

GREEK SCIENTIST
1. Aristotle (384 - 322 B.C) Greek scientist:
Contribution:

• Proposed idea of a substance as a combination of matter and form.
• Describes theory of the Four Elements, fire, water, earth, air.

2. Plato (347 - 428 B.C) Greek scientist:
Contribution:

• Proposed term ‘elements’ as composition of organic and inorganic bodies with particular shape.

3. Democritus (357 - 460 B.C) Greek scientist:
Contribution:

• Proposed the idea of atom, an indivisible particle of matter.

ENGLISH SCIENTISTS
4. Robert Boyle (1627-1691 A.D) English scientist:
Contribution:

• Put forward idea Of chemistry as systematic investigation of nature.
• Discovered the gaseous law.

5. J.Priestly (1733 - 1804 A.D) English scientist:
Contribution:

• Discovered oxygen,sulphur dioxide and hydrogen chloride.

6. John Dalton (1766 -1844 A.D.) English scientist:
Contribution:

• Proposed atomic theory of matter.

SCOTTISH  SCIENTISTS
7. J. Black (1728 -1799 A.D) Scottish scientist:
Contribution:

• Study of carbon dioxide

8. Rutherford (1871 - 1937 A.D Scottish scientist:
Contribution:

• Postulated the nuclear structure of the atom.
• Discovered alpha and beta rays, and proposed the laws of radioactive decay.

GERMAN SCIENTISTS
9. Scheele (1742-1786 A.D) German scientist:
Contribution:

• Discovered chlorine

10. Elbert Einstein (1879 - 1955 A.D) German scientist:
Contribution:

• Proposed fourth state of matter.

BRITISH SCIENTISTS
11. Cavendish (1731-1810 A.D) British scientist:
Contribution:

• Discovered hydrogen

12. M.Faraday (1791 - 1867 A.D) British scientist:
Contribution:

• Contributed to the study of electromagnetism and electrochemistry.

13. J.J.Thomson (1856-1940 A.D) British scientist:
Contribution:

• Discovered the electron by experiments.

14. Neil Bohr (1885 - 1962 A.D) British scientist:
Contribution:

• Proposed a theory for the hydrogen atom based on quantum theory.

FRENCH SCIENTISTS
15. Lavoisier (1743 -1794 A.D) French scientist:
Contribution:

• Discovered that oxygen is one fifth of air

16. Gay-Lussac (1778 - 1850 A.D) French scientist:
Contribution:

• Discovered that water is composed of two parts hydrogen and one part oxygen by volume.
• Discovered several chemical and physical properties of air and other gases.

17. Jacques Charles (1746 - 1823 A.D) French scientist:
Contribution:

• Described the gaseous law.

18. Petit (1741 - 1820 A.D) French scientist:
Contribution:

• Determined the classical expression for the molar specific [heat capacity] of certain chemical elements.

19. De Broglie (1892 - 1987 A.D) French scientist:
Contribution:

• Proposed hypothesis about wave particle duality nature of electron.

ITALIAN SCIENTISTS
20. Avogadro (1776-1856 A.D) Italian scientist:
Contribution:

• Proposed Avogadro’s law that equal volumes of gases under constant temperature and pressure contain equal number of molecules.

SWEDISH SCIENTISTS
21. J.J.Berzellius (1779-1848 A.D) Swedish scientist:
Contribution:

• Introduced symbols, formula and chemical equation to make study more systematic

22. Arrhenius (1859 - 1927 A.D) Swedish scientist:
Contribution:

• Proposed acid base theory and ions dissociation.

RUSSIAN SCIENTISTS
23. Mendeleve (1824-1907 A.D) Russian scientist:
Contribution:

• Discovered periodic arrangement of elements.

AUSTRALIAN SCIENTISTS
24. Schrodinger (1887 - 1961 A.D) Australian scientist:
Contribution:

• Proposed Quantum mechanical model of atom.

INDIAN SCIENTISTS
25. Stendra Nath Bose (1894 - 1974 A.D) Indian scientist:
Contribution:

• Proposed fourth state of matter.

AMERICAN SCIENTISTS
26. Eric Cornell (1961 - Alive) American scientist:
Contribution:

• Synthesized the first Bose Einstein Condensate.

27. Carl weiman (1951 - Alive) American scientist:
Contribution:

• Produced first bose Eienstein Condensate