SENIOR ELEMENTARY TEACHER CHEMISTRY PAST PAPER 11-05-2026
FPSC 5 years
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چار آپشن میں سے کسی ایک پر کلک کرنے سے جواب سرخ ہو جائے گا۔
کاپر کے مرکبات کا نیلا رنگ کس وجہ سے ہوتا ہے؟
- Metallic bonding
- Charge transfer
- d–d transition
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Transition metal compounds show color due to electronic transitions.
- In copper compounds (especially Cu²⁺), d-orbitals are partially filled.
- Electrons absorb specific wavelengths of light and get excited between d-orbitals.
- The remaining reflected/transmitted light appears blue.
- This phenomenon is called d–d transition.
Last verified on 20-05-2026
- Secondary alkyl halide
- Primary alkyl halide
- Methyl bromide
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- SN2 reaction occurs in one step via backside attack.
- Steric hindrance strongly affects reaction rate.
- Less crowded substrates allow easier nucleophilic attack.
- Methyl halides have no alkyl groups blocking the carbon center.
- So they react the fastest in SN2 mechanism.
Last verified on 20-05-2026
ہیس کے قانون کے مطابق اینتھالپی کیوں حساب کی جا سکتی ہے؟
- State function
- Path function
- Intensive property
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Hess’s law states that total enthalpy change is independent of path.
- It depends only on initial and final states of a reaction.
- This is possible because enthalpy does not depend on the route taken.
- Such properties are called state functions.
- Therefore, enthalpy follows path independence.
Last verified on 20-05-2026
پروپین کی اوزونولائسز سے کون سی مصنوعات بنتی ہیں؟
- Ethanol and methanol
- Ethanal and methanal
- Ethanoic acid and methanoic acid
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Ozonolysis breaks the double bond of alkenes using ozone (O₃).
- Propene has structure: CH₃–CH=CH₂.
- Double bond cleavage forms two carbonyl compounds.
- One side gives ethanal (CH₃CHO) and the other gives methanal (HCHO).
- Therefore, these are the final products after ozonolysis.
Last verified on 20-05-2026
الکائل بینزین کو بینزوئک ایسڈ میں تبدیل کرنے کے لیے کیا استعمال ہوتا ہے؟
- NaOH
- KMnO₄, acidified
- H₂/Ni
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Alkyl benzene undergoes side-chain oxidation to form benzoic acid.
- A strong oxidizing agent is required for this conversion.
- Potassium permanganate (KMnO₄) in acidic medium is commonly used.
- It converts the alkyl side chain completely into –COOH group.
- Example: Toluene → Benzoic acid.
Last verified on 20-05-2026
گیبریل فثالیمائڈ سنتھیسس کس کے لیے استعمال ہوتا ہے؟
- 1° amine
- 2° amine
- 3° amine
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Gabriel phthalimide synthesis is a method to prepare amines.
- It involves alkylation of phthalimide followed by hydrolysis.
- This method specifically gives only primary amines.
- It avoids formation of secondary and tertiary amines.
- Therefore, it is a selective and controlled preparation method.
Last verified on 20-05-2026
- r = [A]¹[B]²
- r = [A]²[B]¹
- r = [A]²[B]⁰
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Rate law shows how reaction rate depends on reactant concentrations.
- If rate does NOT change when B changes, then B has no effect on rate.
- This means the order of reaction with respect to B is zero.
- So B appears with exponent 0 in the rate law.
- Therefore, rate depends only on A.
Last verified on 20-05-2026
نائٹرو بینزین کو اینیلین میں تبدیل کرنے کے لیے کون سا ری ایجنٹ استعمال ہوتا ہے؟
- H₂/Ni
- Fe/HCl
- KMnO₄
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Nitrobenzene (C₆H₅NO₂) is reduced to aniline (C₆H₅NH₂).
- Reduction requires removal of oxygen and addition of hydrogen.
- Common lab method uses metals in acidic medium.
- Iron (Fe) with hydrochloric acid (HCl) is widely used (Béchamp reduction).
- It efficiently converts nitro group (–NO₂) to amino group (–NH₂).
Last verified on 20-05-2026
اینڈوتھرمک ری ایکشن کب خود بخود ہوتا ہے؟
- ΔG = +ve
- ΔG = 0
- ΔG = −ve
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Spontaneity of any reaction depends on Gibbs free energy (ΔG).
- Endothermic reaction absorbs heat, but can still be spontaneous.
- The key condition for spontaneity is that free energy must decrease.
- This happens when system moves to a more stable state.
- So ΔG must be negative.
Last verified on 20-05-2026
کون سا کوانٹم نمبر سیٹ درست نہیں ہے؟
- n = 3, l = 3, m = 2, s = 1/2
- n = 4, l = 2, m = 0, s = -1/2
- n = 3, l = 2, m = 1, s = +1/2
- n = 2, l = 1, m = 0, s = -1/2
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Quantum numbers must follow fixed rules.
- For a given principal quantum number n, azimuthal quantum number l = 0 to (n−1).
- If n = 3, possible l values are 0, 1, 2 only.
- So l = 3 is not allowed for n = 3.
- Therefore that set is invalid.
Last verified on 20-05-2026
