Pre-Board Examination Grade 10th Federal SSC II
Subject: Chemistry Class 10
Exam 2024- Solved - Model Paper
Tips, Test Paper, and Guess Paper for Preparation
SECTION-B(Marks 33)
Time:2:40mins
Q2.Answer any eleven questions. Each question carry equal marks
(11x3=33)
i. What are cyclic compounds and their types? Provide examples.
- Definition: Cyclic compounds are organic compounds containing one or more closed rings of carbon atoms in their molecular structure.
- Types:
1. Aliphatic Cyclic Compounds: Examples include cyclohexane and cyclopentane.
2. Aromatic Cyclic Compounds: Examples include benzene and naphthalene.
3. Heterocyclic Compounds: Examples include pyridine and furan.
Condensed Structural Formulas:
- a. Butene: CH3-CH2-CH=CH2
- b. Propyne: CH3-C≡CH
- c. Ethane: CH3-CH3
ii. Define isomers and provide an example.
- Definition: Isomers are molecules with the same molecular formula but different structural arrangements or spatial orientations.
- Example: Structural Isomers: Butane and Isobutane, having the formula C4H10 but different structural arrangements.
iii. What is destructive distillation?
- Definition: Destructive distillation is a process where organic substances are heated in the absence of air to break down complex molecules into simpler ones. This process is commonly used to produce substances like charcoal, coke, and coal tar from organic materials such as wood or coal.
Chemistry Solved SSC-II - Pre-Board Exam - Model Paper - Guess Paper FBISE Class 10
iv. Explain three general characteristics of organic compounds.
1. Contain Carbon and Hydrogen: Organic compounds always contain carbon atoms bonded to hydrogen atoms.
2. Covalent Bonding: Organic compounds typically have covalent bonds between atoms within molecules.
3. Varied Chemical Properties: Organic compounds exhibit a wide range of chemical properties due to the presence of functional groups, allowing for diverse reactions and applications.
v. How does a pharmaceutical chemist analyze a substance for a new drug?
- Pharmaceutical chemists analyze substances for new drugs by conducting experiments to determine their chemical composition, molecular structure, and potential biological activity. Techniques such as spectroscopy, chromatography, and bioassays are used to identify promising compounds for further development.
vi. Name three natural processes that contribute to air pollution.
- 1. Volcanic eruptions
- 2. Forest fires
- 3. Biological activities like pollen release and microbial emissions.
vii. Define global warming and its causes.
- Definition: Global warming refers to the long-term increase in Earth's average surface temperature due to human activities, primarily the emission of greenhouse gases such as carbon dioxide, methane, and nitrous oxide.
- Causes: Burning of fossil fuels, deforestation, and industrial processes are major contributors to global warming.
viii. Define mineral, gangue, and ore.
- Mineral: Naturally occurring inorganic substances with a definite chemical composition and crystalline structure.
- Gangue: The worthless rock or mineral material in which valuable minerals are found.
- Ore: A naturally occurring material from which a mineral or metal can be extracted profitably.
ix. Explain the flotation process.
- Definition: Flotation is a process used to separate minerals from gangue by utilizing differences in their surface properties. It involves adding reagents to create bubbles that selectively adhere to desired mineral particles, allowing them to float to the surface for recovery.
x. Provide sources of carbohydrates.
- Sources of carbohydrates include grains (wheat, rice), fruits (apples, bananas), vegetables (potatoes, carrots), and sugars (sucrose, fructose).
xi. Write steps in raw water treatment.
- Steps in raw water treatment include screening, coagulation, sedimentation, filtration, and disinfection to remove impurities and make water safe for consumption.
xii. Define Le Chatelier’s principle and factors affecting equilibrium of a reversible reaction.
- Le Chatelier’s Principle: This principle states that if a system in equilibrium is subjected to a change in temperature, pressure, or concentration, it will adjust to counteract that change.
- Factors Affecting Equilibrium: Temperature, pressure, concentration of reactants and products, and catalysts influence the equilibrium position of a reversible reaction.
xiii. Write down conditions for equilibrium.
- Conditions for equilibrium include the rates of the forward and reverse reactions being equal, and there is no net change in the concentrations of reactants and products over time.
xiv. What is the importance of Kw?
- Kw is the equilibrium constant for water dissociation. It indicates the extent to which water molecules dissociate into hydronium and hydroxide ions and is crucial for understanding the acidity and alkalinity of aqueous solutions.
xv. Write steps in the manufacturing of urea.
- Steps in the manufacturing of urea involve synthesis of ammonia and carbon dioxide to form ammonium carbamate, which is then dehydrated to produce urea.
SECTION-C (Marks 20)
Attempt any two questions.All questions carry equal marks (2x10=20)
Q3a)Write equilibrium expression and Kc units for following given reaction[4]
C+O2=CO2
b)Describe any two methods for prepration of salts.[4]
c)classify the following substance as lewis acid or lewis base NH3,F-,H2O,BF3
[2]
Q4a)Write genral methods for prepration of alkenes[6]
b)Define functional groups wrire structural formula of propanol.[2]
c)write sources,uses and deficiencies caused by vitamin A[2]
Q5)a)Write methods to remove temporary hardness[4]
b)draw flow chart for solvay process[4]
c)write steps in metallurgical operations[2]
Q3a) Equilibrium Expression and Kc Units:
- Question: Write the equilibrium expression and Kc units for the following reaction: C + O2 ⇌ CO2
- Answer:
- Equilibrium Expression: [CO2] / [C][O2]
- Kc Units: The concentration of CO2 divided by the product of the concentrations of C and O2, all raised to their respective stoichiometric coefficients.
b) Methods for Preparation of Salts:
- Question: Describe any two methods for the preparation of salts.
- Answer:
- Method 1: Neutralization Reaction: Reacting an acid with a base to form a salt and water. Example: HCl + NaOH → NaCl + H2O.
- Method 2: Direct Combination: Reacting a metal with a non-metal to form a salt. Example: Mg + Cl2 → MgCl2.
c) Classification of Lewis Acids or Bases:
- Question: Classify the following substances as Lewis acids or Lewis bases: NH3, F-, H2O, BF3.
- Answer:
- Lewis Acids: BF3 (accepts electron pairs).
- Lewis Bases: NH3, F-, H2O (donates electron pairs).
Q4a) General Methods for Preparation of Alkenes:
- Question: Write general methods for the preparation of alkenes.
- Answer:
- Method 1: Dehydration of Alcohols: Heating alcohols in the presence of a strong acid catalyst to eliminate water and form alkenes.
- Method 2: Dehydrohalogenation of Haloalkanes: Treatment of haloalkanes with a strong base to remove a hydrogen halide and form alkenes.
b) Definition of Functional Groups and Structural Formula of Propanol:
- Question: Define functional groups and write the structural formula of propanol.
- Answer:
- Functional Groups: Functional groups are specific atoms or groups of atoms within a molecule that determine its chemical properties. Example: -OH group in alcohols.
- Structural Formula of Propanol: CH3-CH2-CH2-OH
c) Vitamin A Sources, Uses, and Deficiencies:
- Question: Write sources, uses, and deficiencies caused by vitamin A.
- Answer:
- Sources: Liver, fish oils, dairy products, carrots, spinach.
- Uses: Essential for vision, immune function, and skin health.
- Deficiencies: Night blindness, dry skin, impaired immune function.
Q5a) Methods to Remove Temporary Hardness:
- Question: Write methods to remove temporary hardness.
- Answer:
- Method 1: Boiling: Temporary hardness can be removed by boiling the water, causing the calcium and magnesium bicarbonates to decompose into insoluble carbonates, which can then be removed by filtration.
- Method 2: Addition of Lime: Adding calcium hydroxide (lime) to the water to precipitate calcium carbonate, which can be removed by filtration.
b) Flow Chart for Solvay Process:
- Question: Draw a flow chart for the Solvay process.
- Answer:
- Explanation of the Solvay Process: (Include steps like ammonia absorption, brine purification, etc.)
c) Steps in Metallurgical Operations:
- Question: Write steps in metallurgical operations.
- Answer:
- Step 1: Crushing and grinding of the ore.
- Step 2: Concentration of the ore by froth flotation or gravity separation.
- Step 3: Reduction of the ore to obtain the metal (e.g., smelting).
- Step 4: Refining of the metal to remove impurities.
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