Chemistry Exam Questions PDF

# Basic Science (Chemistry) ## Q1) Small answer questions: a) Explain Kanada theory of atom. - First atom was discovered by Acharya Khand in (600 BC to 800 BC). - He was said that on dividing matter we got smaller particles of matter & smaller particle which cannot be divided known as parmanu ato...

# Basic Science (Chemistry) ## Q1) Small answer questions: a) Explain Kanada theory of atom. - First atom was discovered by Acharya Khand in (600 BC to 800 BC). - He was said that on dividing matter we got smaller particles of matter & smaller particle which cannot be divided known as parmanu atoms. - **Kanada theory of atom is as follows:** - **Param** = Ultimate & **Anu** = particles, hence matter consist of indestrible particle called paramanu.
 - Everything can be partitjoined, parmanu does not exist in Free state.
 - Paramanu are tiny particles, atom is minute object, invisible, indestructable & hence never ending.
 - Paramanu cannot be Further subdivided & when paramanu & paramany get added the molecule is formed.
 - It has two states First is state of motion & second is state of Absoluterest. ## Q2) Define the following term:- i) Valence electron:
 - The element or electrons present in the outermost orbit of an atom of an element that determines the valency is called valence electron. ii) Octate rule: - The tendency of atom to prefer to have eight electrons in the valence shell is known as octate rule. ## Write difference between amorphous & crystalline solids: | No. | Amorphous Solids | Crystalline Solids | |---|---|---| | 1. | It shows definite arrangement of atoms/ions/molecules.| It shows random arrangement of atoms/ions / molecules. | | 2. | It have sharp melting point | It Do not have sharp melting pt. | | 3. | It have definite geometry. | It do not have definite geometry. | | 4. | It is Anisotropic. | It is Isotropic. | | 5. | It have uniform cleavage. | It do not have uniform cleavage. | | 6. | e.g. NaCl, diamond, graphite. | e.g. Glass, rubber, plastic. | ## d) Define unit cell write its parameter. (col). - **Unit cell:** - Smallest basic three dimensional [3D] repeating unit when repeating in different direction producing complete crystal lattice. - It shows shape of entire crystal obtained by extending the unit cell in all three directions. - So, it is a box in which particles may be located at Corners, Faces & center of the box. - **Parameter of unit cell:** - Length along three edges = a, b, c - Angles along three axes = α, β, γ = 90° (x, y, z) ## e) Define the following: ### Electrolysis: - The process by which electric current is passed through a substance to effect a chemical change. ### Electrode potential: - [The potential difference across the interface between the electrode and its solution is called electrode potential.] ## Q2 Medium answer question: a) Explain the formation of: i) MgO molecule. - **12Mg** → Electronic Configuration (2,8,2) - No. of valence electrons = 2 - To, attain stable configuration of nearest inest gas 10Ne, Mg atom loser its two ee Forming Mg**+** charge. - Mg —-> Mg**+** + 2e0 - (2,8,2) (2,8) - **8O** → Electronic Configuration = (2,6) - No. of valence electrons = 6 - To, attain stable electronic configuration of nearest inest gas 10 Ne, oxygen atom gains 2e0. - O + [2e0-] → O**-** - (2,6) (2,8) - Mg**+** + O**-** -> Mg - O - (2,8,2) (2,6) (2,8) (2,8) - [Ne] [10Ne] ii) C2H2 molecule: - Ethyne molecule have 2C & 2H atoms.. - **6C** —> 1s² 2s², 2p² (2,4) - valence electrons = 4. - **1H** —> 1s¹ - (1) valence electrons=1 - Each, carbon requires 4e for octet completion while each H atom requirs 1e0 For duplete. - Thus, molecule is formed by sharing 3e0 pairs bet" 2C atom Forming triple covalent bonds & 1e0 pair with It atom each Forming single covalent bonds. - H * + C : + C : + H —> - H —> C = C <— H - C2H2 molecule ## Write short note on hydrogen bond: - The bond is formend be electrostatic force of attraction bet" hydrogen and electronegative atoms (N.O.F) is called as hydrogen bond. - So, electron pair is shared between electro-positive hydrogen atom & highly electronegative O/F/N atom Forming partial +ve charge on H atom & -ve charge on electronegative O/N/F atoms. - e.g. Formation of HF molecule:- - Here, In HF molecule F is highly electronegativen in nature so it aquires -ve charge while H atom aquires +ve charge, hence they behave like a dipble when two HF molecule come close to each other they Forms electrostatic atteaction bet" H & F atom of both molecules Forming weak bond know as Hydrogen bond or Hydrogen bridge. - H − F + H − F —> H − F − H − F —> H − F —- (CH) n. - Hydrogen - bond - Hydrogen bond is denoted by dotted lines (----)- ## d) Explain molecular arrangement in solids: - Solied particles are packed close to each other only they make small vibrational movement about their Fixed positions. The spaces between particles are Known as intermolecular spaces due to this particles attracts each other very strongly & tree movement Of particles is not possible. - Hence, solids are rigid & retain their shape. - e-g. metals, Ionic solides, etc. ## Q3) Long answer question: a) Explain with neat labeled diagrams types of crystal system. - [A diagram illustrating various types of crystal system e.g. Cubic, Tetrahedral, Trigonal, etc, would be necessary for the user to understand.]