9th Class Chemistry Important Questions Answers

1 Differentiate between Physical Chemistry and Biochemistry?

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 is called physical chemistry.

Biochemistry: The branch of chemistry which deals with the study of structure, composition and chemical reactions of substances found in living organisms is called biochemistry.

2 Define Organic and Environmental Chemistry?

Organic chemistry: Organic chemistry is the study of covalent compounds of carbon and hydrogen (hydrocarbons) and their derivatives

Environmental chemistry: It is the branch of chemistry in which we study about components of the environment and the effects of human activities on the environment

3 Define Empirical Formula and Molecular Formula?

Empirical Formula: The simplest form of chemical formulas is called empirical formula. It represents the simplest whole number ratio of atoms present in a compound. Empirical formula of benzene is CH.

Molecular Formula: Molecules are formed by the combination of atoms These molecules are represented by molecular formula that show actual number of all S present in a molecule of that compound Molecular formula of benzene is C6H6.

4 Calculate the Molecular Mass of Nitricacid. (HNO3),

Atomic mass of H-1 amu Atomic mass of N 14 amu

Atomic mass of O = 16 am

Molecular formula = HNO,

molecular mass = (atomic mass of (H) + (atomic

mass of N) + 3 (atomic mass of O)

= 1 + 14 + 3(15)

* 15 + 48+63amu

5 What is a Mixture? Give one example.

When two or more elements or compounds mix up physically without any fixed ratio they form a mixture e g. Air

6 Define Homogeneous and Heterogeneous mixture?

Homogeneous mixture: Those mixtures which have uniform composition of components, throughout are called homogeneous mixtures e.g air, gasoline ice cream, etc

Heterogeneous mixture: Those in which composition of components is not uniform throughout e.g soil, wood, rock, etc

7 Write two significance of Formula?

It shows the elements present in compound nts present in the or formula properties and give the composition ance under transition change BE.

It represents molecule or form symbolcallying.

8 Define Chemical Properties and Example.

Chemical properties: The chemical properties depend upon the composition of the substance When a substance under a chemical change its composition change and a new substance is formed.

9 Write down the Symbols of Sodium and Hydrogen?

Sodium = Na,

Hydrogen = H

10 Write down the Chemical formula of Silicon Dioxide and Calcium Chloride.

Silicon dioxide SIO .

Calcium chloride Cacl.

11 Write the name of two elements which occur in liquid state on Room Temperature.

Bromine (Br)

Mercury (Hg)

12 Define Valency with an example?

The combining capacity of an element other element is called valency Example: Valency of carbon is 4.

13 Calculate the number of moles of 1496 chemical nitrogen gas?

Molar mass of N2 = 289

Given mass = 149

Number of mole of N = Given mass / mos

mass

= 14/28 = 0.5 moles

14 Define industrial and Nuclear Chemistry?

Industrial chemistry: The branch of chemistry that deals with the study of preparation of compounds on methods of preparation on commercial scale is known as industrial chemistry.

Nuclear chemistry: A branch of ls with study of radioactivity ions and properties of ions

15 Define Molecular Ion. Give an example?

Molecular lon: When one or two molecules escape from elements.

16 Write the names of elements arranged in group first of Periodic Table?

The first group of periodic table consist of Hydrogen, Lithium, Sodium, Potassium, Rubidium, Cesium and Francium.

17 Write any two features of long form of Periodic Table?

This table consist of seven horizontal rows called periods.

The elements of a group show similar chemical properties.

18 Write the names of any four P-block Elements?

Boron, Carbon, Nitrogen, Oxygen.

19 State Mendeleeve, Periodic Law?

The properties of elements are the periodic function of their atomic masses.

20 What do you mean by group in the Periodic Table?

In periodic table the vertical columns are called groups.