LECTURER CHEMISTRY PAST PAPER 24-04-2024 BY SPSC
Lecturer Chemistry
چار آپشن میں سے کسی ایک پر کلک کرنے سے جواب سرخ ہو جائے گا۔
- Zero
- First
- Second
- Third
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Explanation
- The free radical substitution reaction of CH₄ with Cl₂ is a zero-order reaction.
- Its rate does not depend on the concentration of reactants under steady conditions.
- The reaction proceeds via chain mechanism (initiation, propagation, termination).
- So overall observed order is zero.
Last verified on 05-06-2026
- 34 moles/kg
- 24.2 moles/kg
- 20 moles/kg
- 28 moles/kg
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Explanation
Molality m = moles of solute / kg of solvent
For 60% w/w solution, take 100 g solution:
1) Solute: 60 g ethylene glycol C₂H₆O₂
Molar mass = 2(12) + 6(1) + 2(16) = 62 g/mol
Moles EG = 60 / 62 ≈ 0.9677 mol
2) Solvent: 40 g water = 0.040 kg
3) Molality
m = 0.9677 mol / 0.040 kg ≈ 24.2 mol/kg
Last verified on 05-06-2026
مندرجہ ذیل مائعوں کے جوڑوں میں سے کون سا جوڑا راؤلٹ کے قانون کی پیروی نہیں کرتا؟
- Methanol and ethanol
- Benzene and toluene
- n-hexane and n-octane
- Propanol and propanone
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Explanation
- Propanol and propanone do not obey Raoult’s Law.
- They form a non-ideal solution due to strong intermolecular interactions.
- Hydrogen bonding and polarity differences cause deviation.
Last verified on 05-06-2026
وہ نمک جو کمزور تیزاب اور کمزور بنیاد کے بے اثر ہونے سے بنتا ہے کون سا ہے؟
- Nacl
- CH₃COONa
- (NH₄)₂CO
- None of these
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Explanation
- A salt from weak acid + weak base is ammonium carbonate.
- It is formed from carbonic acid (weak acid) and ammonia (weak base).
- Both ions hydrolyze in water.
- So it is a typical weak acid–weak base salt.
Last verified on 05-06-2026
- 90.9%
- 85.9%
- 50%
- 80%
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Explanation
Esterification: CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O Acetic acid : Ethyl acetate = 1 : 1 mole ratio
1) Molar masses
Acetic acid CH₃COOH ≈ 12+3+12+16+16+1 = 60 g/mol
Ethyl acetate CH₃COOC₂H₅ ≈ 88 g/mol
2) Theoretical yield
30 g acetic acid = 30/60 = 0.5 mol
So 0.5 mol ethyl acetate should form = 0.5 × 88 = 44 g
3) % Yield
% Yield = (Actual / Theoretical) × 100
= (40 / 44) × 100 ≈ 90.9%
Last verified on 05-06-2026
کرومیٹوگرافک تجزیے میں کون سا اصول استعمال ہوتا ہے؟
- Absorption
- Distribution
- Adsorption
- Evaporation
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Explanation
- Chromatography mainly works on the principle of adsorption.
- Different substances are adsorbed to different extents on a stationary phase.
- This causes separation of components in a mixture.
Last verified on 05-06-2026
لوئری اور برونسٹیڈ تھیوری کے مطابق یوریا ایک ایمفی پروٹک سالونٹ ہے۔ جب یہ امونیا کے ساتھ ردعمل کرتا ہے تو یہ کس طرح عمل کرتا ہے؟
- Acid to form
- Base to form
- Neutral to form
- Amphoteric to form
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Explanation
- Urea acts as an acid when it reacts with ammonia.
- According to Brønsted–Lowry theory, acids donate protons (H⁺).
- Ammonia acts as a base and accepts the proton.
- So urea behaves as a proton donor in this reaction.
Last verified on 05-06-2026
اینٹی الرجک دوائیں اینٹی ہسٹامینز بھی کہلاتی ہیں۔ جسم میں ہسٹامین کس عمل کے ذریعے بنتا ہے؟
- Deamination of amino acids
- Decarboxylation of amino acids
- Transamination of amino acids
- Decarboxylation of fatty acids
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Explanation
- Histamine is produced in the body from amino acids.
- It is formed by decarboxylation of histidine.
- Histamine is responsible for allergic reactions.
- Antihistamines block its effects in the body.
Last verified on 05-06-2026
- Cl° and C° F2Cl
- Cl° and O°
- Cl2CF° and C° l
- C° lO + F°
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Explanation
- UV radiation breaks CFC molecules in the atmosphere.
- This produces chlorine radicals (Cl•) and CF₂Cl• radicals.
- Chlorine radicals are responsible for ozone depletion.
- They catalytically destroy ozone molecules in the stratosphere.
Last verified on 05-06-2026
مندرجہ ذیل میں سے کون سا عمل ٹاٹومیریزم کو ظاہر کرتا ہے؟
- CH3COOH + C2H5OH ⇌ CH3COOC2H5 + H2O
- N2 + 3H2 ⇌ 2NH3
- CH3 – CH = CH – CH3 ⇌ CH3 – CH2 – C – CH3
- None
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Explanation
- Tautomerism is the interconversion of two isomers by shifting a hydrogen atom and double bond.
- It usually occurs in compounds like alkenes, carbonyls, etc.
- Correct type shown in: CH3–CH=CH–CH3 ⇌ CH3–CH2–C–CH3
Last verified on 05-06-2026
