SENIOR ELEMENTARY TEACHER SET PAST PAPERS AND SYLLABUS
چار آپشن میں سے کسی ایک پر کلک کرنے سے جواب سرخ ہو جائے گا۔
حل پذیری اور سختی کے بارے میں کیا درست ہے؟
- Increases solubility and decreases rigidity
- Decreases solubility and increases rigidity
- Increases both solubility and flexibility
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Solubility and rigidity depend on molecular structure and bonding.
- Flexible structures allow better interaction with solvent molecules.
- Increased flexibility generally improves solubility.
- More rigidity reduces molecular movement and solubility.
Last verified on 19-05-2026
نائلون 6,6 کی تیاری میں کون سے دو کیمیکل استعمال ہوتے ہیں؟
- Adipic acid and Hexamethylenediamine
- Terephthalic acid and Ethylene glycol
- Caprolactam and Water
- None of these
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Explanation
- Nylon 6,6 is a synthetic polyamide polymer.
- It is formed by condensation polymerization.
- Two monomers react to form long polymer chains.
- Nylon 6,6 is formed by condensation of adipic acid (diacid) and hexamethylenediamine (diamine).
- Each monomer contributes 6 carbon atoms (hence 6,6).
- Water is eliminated during the reaction.
Last verified on 19-05-2026
پولی اسٹائرین کا مونومر کیا ہے؟
- Ethene
- Propene
- Styrene
- None of these
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Explanation
- Polystyrene is a common synthetic polymer used in plastics and packaging.
- It is formed by addition polymerization.
- The repeating unit comes from a specific aromatic monomer.
- This monomer is called styrene (vinyl benzene).
- Hence, polystyrene is derived from styrene.
Last verified on 19-05-2026
- Carboxylic acid
- Alcohol
- Aldehyde
- None of these
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Explanation
- Grignard reagents (RMgX) are strong nucleophiles.
- They react with carbon dioxide (CO₂) to form magnesium carboxylate.
- After acidic workup (H₃O⁺), carboxylic acid is produced.
- This is an important method to increase carbon chain length.
- It always forms acids after hydrolysis.
Last verified on 19-05-2026
- Spontaneous
- Non-spontaneous
- At equilibrium
- None of these
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Explanation
- Reaction spontaneity is determined by Gibbs free energy (ΔG).
- Formula: ΔG = ΔH − TΔS
- If ΔG is positive, reaction is non-spontaneous.
- If ΔG is negative, reaction is spontaneous.
- Here entropy is positive but not enough to overcome enthalpy.
Last verified on 19-05-2026
- 100.256°C
- 100°C
- 101.256°C
- None of these
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Explanation
- ΔTb = Kb × m × i = 0.512 × 0.5 × 1 = 0.256°C
- Boiling point = 100 + 0.256 = 100.256°C.
Last verified on 19-05-2026
کسی مادے کا ٹرپل پوائنٹ کیا ہوتا ہے؟
- Point where solid, liquid, and gas coexist in equilibrium
- Point where only solid and liquid coexist
- Point where only liquid and gas coexist
- None of these
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Explanation
- The triple point is a special thermodynamic condition of a substance.
- At this point, all three phases exist together.
- These phases are solid, liquid, and gas.
- They remain in equilibrium at a specific temperature and pressure.
- It is a fixed and unique point for each substance.
Last verified on 19-05-2026
کس ری ایکشن میں ری ایکٹنٹس کے تمام ایٹم پروڈکٹ میں شامل ہوتے ہیں؟
- Combustion of methane
- Hydrogenation of alkene
- Substitution reaction
- None of these
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Explanation
- In some chemical reactions, all atoms of reactants are completely retained in the final product.
- No atom is lost or removed during the reaction.
- Such reactions are typically addition reactions.
- Hydrogenation of alkenes is a common example.
Last verified on 19-05-2026
اروماتک نائٹریشن میں کون سا الیکٹروفائل استعمال ہوتا ہے؟
- NO⁺
- NO₂⁻
- NO₂⁺
- None of these
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Explanation
- The active electrophile in nitration of benzene is nitronium ion (NO₂⁺).
- It is generated from a mixture of concentrated HNO₃ and H₂SO₄.
Last verified on 19-05-2026
- −Ea/R
- +Ea/R
- −R/Ea
- None of these
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Explanation
- The Arrhenius plot relates the rate constant (k) with temperature (T).
- When we plot ln k vs 1/T, we get a straight line.
- Whose slope is negative activation energy divided by gas constant.
Last verified on 19-05-2026
