Federal Board Class IX

SECTION “A”

Q.1. Insert the correct option i.e. A/B/C/D in the empty box provided opposite each part. Each part carries one mark.

i. What is the number of water molecules present in one mole of potash alum crystal?

• 20
• 24
• 28
• 30

ii. What is the gas that evolves at the anode during the electrolysis of aqueous NaCl?

• Cl₂
• H₂
• O₂
• HCl

iii. What is the process of dissolving a solute in a solvent called?

• Solution
• Crystallization
• Dissolution
• Solubility

iv. What is the number of elements in the second period of modern periodic table?

• Ten
• Two
• Eighteen
• Eight

v. Cooling the vapour of some compounds changes them directly into solid state. What is this phenomenon called?

• Condensation
• Evaporation
• Sublimation
• Boiling

vi. Which is the most reactive non-metal?

• Chlorine
• Oxygen
• Fluorine
• Hydrogen

vii. The molecular formula of oxalic acid is C₂H₂O₄. Which of the following formulas represents its empirical formula?

• CH₂O₂
• CHO
• C₂HO₂
• CHO₂

viii. What is the information obtained from observation called?

• Facts
• Theory
• Principles
• Knowledge of science

ix. What NO₂-1 the formula of?

• Nitrate
• Nitrous oxide
• Nitrogen dioxide
• Nitrite

x. Which of the following statements is incorrect about the structure of NH₄Cl?

• A hydrogen bond is present in it
• A covalent bond is present in it
• A coordinate covalent bond is present in it
• An ionic bond is present in it.

xi. What is the molecular mass of heavy water?

• 18.02
• 20.03
• 22.02
• 16.05

xii. What is the abundance of chlorine-35 in nature?

• 100%
• 50%
• 75%
• 25%

SECTION “B”

Q.2. Attempt any ELEVEN parts. The answer to each part should not exceed 3 to 4 lines. (33)

i. Modern periodic table is a modified form of Mendeleev’s periodic table.

a. Give an difference between Modern and Mendeleev’s periodic table. (01)
b. What is the position of Lanthanides and actinides in modern periodic table? (01)
c. Into how many blocks is the modern periodic table divide? (01)

ii. William Crooks performed experiments for the discovery of electron.

a. At what pressure was the gas placed in the discharged tube? (01)
b. Draw and label the discharged tube. ½ + ½.
c. Write any two properties of cathode rays. ½ + ½

iii. Complete and balance the following equations.

a. Zn(NO₃)₂ ——–> (01)
b. CaCO₃ + HCl ——-> (01)
c. KBr + Cl₂ ——–> (01)

iv. Some elements exist in the form of atoms whereas other exist as combination of atoms.

a. Give the new definition of atomic mass. (01)
b. Calculate the molecular or formula masses of the following compounds (1 + 1)
Na₂CO₃. (NH₄)₂SO₄ (Atomic mass of Na=23, C=12, N=14, H=1, S=32)

v. When acids neutralize bases, salts and water are formed.

a. What are double salts? Define. Write two names and formula of double salts. (1+½+½).
b. If the acidity of soil increases due to some reasons, then to reduce this effect, farmers add a compound into the soil. Write its name and formula. (½+½).

vi. An atom is a neutral particle. It contains electrons, protons and neutrons.

a. Define Isotope. Name the scientist who suggested the name “isotope” for the first time. (1+½).
b. Draw the isotopes of oxygen. (1.5)

vii. A chemical bond is a force of attraction between atoms which holds them together in the form of a molecule or a compound.

a. Write down the formulas of the compounds formed by the reactions of carbon with hydrogen and carbon with chlorine. Explain their electronic structures. (1+1)
b. Define co-ordinate covalent bond. (01)

viii. (a) Write down a balanced chemical equation for the reaction of phosphoric acid H₃PO₄ with calcium hydroxide Ca(OH)₂ to produce water and calcium phosphate Ca₃(PO₄)₂. (01)
b. Find out the mass of calcium hydroxide required to react completely with 20g of phosphoric acid. (01)
(Atomic mass of H=1, P=31, O=16, Ca=40)

ix. Micheal Faraday’s published two laws about electrolysis.

a. State Faraday’s first law of electrolysis. (01)
b. Write balanced chemical equations for the reaction involved in silver plating. Also write the name of the electrolyte used. (1.5+0.5)

x. A homogeneous mixture of different chemical substances is called a solution.

a. Define Solubility. (01)
b. Explain dissolution of compounds through hydrogen ponding. (02)

xi. In the chemical reaction a large number of atoms of molecules of reactants react to give products.

a. How can you define a mole and molar mass. (1/2 + 1/2)
b. How many moles of oxygen gas will be utilized by 1.80 moles of ethyl alcohol C₂H₅OH when burnt in air completely? (02)

xii. All the electrons present in the atoms of elements can be allocated to particular shells and sub-shells.

a. What is Aufbau principle? (01)
b. Write and draw the electronic configuration of the following. (01+01)
40Ca, 23Na
20…. 41

xiii. The branch of chemistry which deals with heat changes is called thermo chemistry.

a. Define exothermic reaction (01)
b. What is meant by enthalpy of a reaction? (01)
c. Name the factors on which enthalpy of a substances depends. (1/2+1/2)

xiv. The search of man for collecting knowledge and integrating it, is called science.

a. Define organic and inorganic chemistry. (1/2+1/2)
b. How is chemistry proved to be dangerous for our lives? Give any two points? (01+01)

xv. Physical and chemical properties of elements gradually change in groups and periods.

a. Define ionization energy. (01)
b. What is the trend of ionization energy in groups and periods? (01+01)

SECTION “C”

NOTE: Attempt any TWO questions. (20)

Q.3. Define a covalent bond. Explain the types of covalent bonds with one example of each. Write down the properties of covalent compounds.

Q.4. Write the experiment performed by Rutherford for the discovery of atomic nucleus. Also write its conclusions. Draw a labeled diagram for this experiment. Give the drawbacks of this atomic model.

Q.5. Explain how sodium carbonate is prepared on industrial scale. Also draw a flow sheet diagram for its preparation.