IX Chemistry

NOTE: Attempt Fourteen questions in all SEVEN questions from SECTION “A”, SIX from SECTION “B” and the compulsory Q.1. All questions of SECTION “A” and “B” carry equal marks.

OBJECTIVE (Compulsory)

Q.1 (A) Fill in the blanks with the correct answers.
i. The chemical formula of baking soda is NaHCO3.
ii. Bases are electron pair acceptors.
iii. One faraday = 96500 columbs.
iv. Organic Chemistry is the chemistry of hydrocarbons and their derivates.
v. Robert Boyle is called the “Father of Modern Chemistry”.

Q.1 (B) Select the correct answer for each from the options given within brackets.
i. A suspension of the particles of carbon in air is called smoke.
(foam, mud, smoke, emulsion)
ii. 5 moles of H2O are equal to 90g.
(80g, 90g, 100g, 90amu)
iii. Which particles is the lightest in the following?
(electron, Proton, Neutron, Alpha)
iv. The only liquid metal is Mercury
(Gold, Silver, Mercury, Bromine)
v. Molten-iron on cooling changes into solid-iron, it is an example of Freezing.
(Sublimation, Melting, Boiling, Freezing)

SECTION “A” (Short Answer Questions)

Q.2 What is Chemical Reaction? Define and give one example each of the following chemical reactions.
i. Addition Reactions
ii. Decomposition Reactions

Q.3 Balance the following chemical equations.
i. NH3 + O2 ——> NO + H20
Ans. 4NH3 + 502 ——> 4 NO + 4H2O

ii. PCl3 + H2O ——> H2PO3 + HCl
Ans. PCl3 + 2H2O ——> H3PO23 + HCl

iii. Pb(NO3)2 ——> PcO + NO2 + O2
Ans. 2Pb (NO3)2 ——> 2PbO + 4NO2 + O2

iv. KI + MnO2 + H2SO4 ——> K2SO4 + MnSO4 + H2O
Ans. 2Kl + MnO2 + 2H2O4 ——> K2SO4 + MnSO4 + 2H2O

v. Zn + HNO3 ——> Zn(NO3)2 + H2O + NH4NO3
Ans. Zn + 8HNO3 ——> Zn(NO3)2 + 2H2O + NH4NO3

Q.4. State the Law of Multiple Proportions and the Law of Reciprocal Proportions and explain any one of them with the help of an example.

Q.5. What is an Chemical Bond? Define an Ionic Bond. Explain the mechanism of formation of the ionic bond in NaCl.

Q.6. Describe Rutherford’s experiment which led him to the discovery of the nucleus of an atom.

Q.7. What is a Coordinate Covalent Bond? How is a coordinate covalent bond formed between ammonia (NH3) and hydrogen ion (H+) producing ammonium (NH4+) radical? Explain.

Q.8. Write five general properties of the elements of Group VII A of the periodic table.

Q.9. What is meant by Radioactivity? Draw a labelled diagram showing the separation of Alpha, Beta and Gamma Rays. Also write two properties of each of these rays.

Q.10. Define the following:
i. Periodicity
ii. Atomic Radius
iii. Electro Negativity
iv. Electron Affinity
v. Ionization Potential

Q.11. “Chemistry and human society go hand in hand”. Write five arguments in support of this statements.

Q.12. State the following:
i. Debereiner;s Law of Triads
ii. Newland’s Law of Octaves
iii. Mendeleev;s Periodic Law
iv. Modern Periodic Law
v. Law of Constant Composition

Q.13. Write the name of any five renowned scientists of the world and write one contribution of each of them in the development of Chemistry.

SECTION “B” (Short Answer Questions)

Q.14. State and explain Faraday’s Second Law of Electrolysis.

Q.15. State Bronsted-Lowry Theory of Acids and Bases and explain it with the help of the examples of HCl and HN3.

Q.16. Write five difference between a Solution and Suspension.

Q.17. Define a “Thermo Chemical Reaction”. What is meant by “Enthalpy of a Reaction”. Also define Endothermic Reaction and give its two examples.

Q.18. Define the following:
i. Sublimation
ii. Evaporation
iii. Diffusion
iv. Brownian Movement
v. Boiling Point

Q.19. A current of 5 amperes was passed through a solution of CuSO4 for an hour. Find the mass of copper metal deposited on the cathode. The electrochemical equivalent of copper is 0.000329g/c.

Data
Electric Current = A = SA
Time = t = 1h = 1 x 60 x 60 = 3600 sec
Electrochemical Equivalent = z 0.000329 g/c = 3.29 x 10-4 g/c
Mass of Copper metal = W = ?

Solution
.. W = ZAt
=> W = 3.29 x 10-4 x 5 x 3600
=> W = 59220 x 10-4
=> W = 59220 / 10000
=> W = 5.922 g ANS

Q.20 What is a double salt? Write the chemical formulae of the following salts.
i. Potash alum
ii. Chrome alum
iii. Carnalite
iv. Mohr’s salt

Q.21. Define the following:
i. Heat of Neutralization
ii. Ampere
iii. Exothermic reaction
iv. faraday
v. Coulumb

Q.22. Define Morality. Calculate the morality of a solution which contains 5.3 g of Na2CO3 in 500 ml solution (At: Masses: Na = 23, C = 12, 0 = 16)

Data
Mass of solute (NaCO3) = 5.3 g
Molecular mass of Na2CO3 = ?
Volume of Solution = 500 ml

Solution
Molecular Mass = 2 x 23 + 1 x 12 + 3 x 16
= 46 + 12 + 48
= 106
Molarity = Mass of Solute / Molecular Mass x Volume of Solution
=> Molarity = 5.3 / 106 x 500
=> Molarity = 5.3 / 53000
=> Molarity = 0.0001 M ANS

Q.23. With the help of a labelled diagram explain the construction and working of a Dry Cell.