SENIOR ELEMENTARY TEACHER SET PAST PAPERS AND SYLLABUS
چار آپشن میں سے کسی ایک پر کلک کرنے سے جواب سرخ ہو جائے گا۔
ان میں سب سے مضبوط لیگنڈ کون سا ہے؟
- Cl⁻
- H₂O
- CN⁻
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Ligands are ions or molecules that donate electron pairs to metal ions.
- Their strength is explained by the spectrochemical series.
- Strong ligands cause greater splitting of d-orbitals.
- CN⁻ produces strong crystal field splitting and electron pairing.
- Therefore, it is considered a strong field ligand.
Last verified on 19-05-2026
- Square planar and paramagnetic
- Tetrahedral and paramagnetic
- Square planar and diamagnetic
- None of these
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Explanation
- In this complex, nickel is in +2 oxidation state.
- Ni²⁺ has electronic configuration: 3d⁸.
- CN⁻ is a strong field ligand and causes electron pairing.
- This leads to dsp² hybridization with square planar geometry.
- All electrons become paired, making the complex diamagnetic.
Last verified on 19-05-2026
کون سا آئن سب سے زیادہ غیر جفت الیکٹران رکھتا ہے؟
- Mn²⁺
- Fe²⁺
- Co²⁺
- None of these
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Explanation
- Unpaired electrons depend on d-orbital electronic configuration.
- Mn²⁺ has configuration: [Ar] 3d⁵.
- According to Hund’s rule, all five d-electrons remain unpaired.
Last verified on 19-05-2026
کون سا مالیکیول 120° کے قریب بانڈ اینگل رکھتا ہے؟
- CH₄
- NH₃
- BF₃
- None of these
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Explanation
- Bond angle depends on molecular geometry and electron pair repulsion.
- Trigonal planar molecules have bond angles close to 120°.
- BF₃ has no lone pair on central atom, so perfect trigonal planar shape.
Last verified on 19-05-2026
سب سے زیادہ آئنک خصوصیت کس میں ہے؟
- KBr
- LiF
- NaCl
- None of these
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Explanation
- Ionic character depends on electronegativity difference between atoms.
- Greater difference → more ionic nature.
- Lithium (Li) and Fluorine (F) have a very large electronegativity gap.
- Small size of Li⁺ also increases polarizing power, but F⁻ is very electronegative.
- So LiF shows the strongest ionic bond among given options.
Last verified on 19-05-2026
ایتھانول اور ایتھانوئک ایسڈ کے ردِ عمل سے بننے والا ایتھائل ایسیٹیٹ کس قسم کا ردِ عمل ہے؟
- Neutralization
- Hydrolysis
- Esterification
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Ethyl acetate is an ester compound.
- It is formed when an alcohol reacts with a carboxylic acid.
- Ethanol + ethanoic acid undergo a condensation reaction.
- Water is removed during the formation of ester.
- This process is commonly called ester formation.
Last verified on 19-05-2026
خود بخود ہونے والے ردِ عمل کے لیے گِبس فری انرجی کیا ہوتی ہے؟
- Negative
- Positive
- Zero
- None of these
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Explanation
- Gibbs free energy (ΔG) determines spontaneity of a reaction.
- A reaction is spontaneous when it can proceed on its own.
- For spontaneity, energy must be released during the process.
- This means the system moves toward lower energy state.
- Therefore, ΔG must be less than zero.
Last verified on 19-05-2026
- Decrease
- Remain constant
- Increase
- None of these
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Explanation
- Gibbs free energy change depends on reaction quotient (Q).
- Relation: ΔG = ΔG° + RT ln Q.
- When Q increases, ln Q increases.
- This makes ΔG more positive.
- So the system becomes less spontaneous in forward direction.
Last verified on 19-05-2026
کون سا آربٹل سب سے زیادہ مؤثر نیوکلیئر چارج محسوس کرتا ہے؟
- 3s
- 3p
- 3d
- None of these
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Explanation
- Effective nuclear charge (Zₑff) is the net positive charge felt by an electron.
- It increases when shielding is less and penetration is higher.
- For a given shell (n = 3), penetration order is: 3s > 3p > 3d.
- 3s electrons are closest to the nucleus and least shielded.
- Therefore, they experience the strongest attraction from the nucleus.
Last verified on 19-05-2026
- Inversion of configuration; rate depends on both substrate and nucleophile
- Racemization; rate depends only on substrate
- Retention of configuration; rate depends only on nucleophile
- None of these
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Explanation
- SN2 is a bimolecular nucleophilic substitution reaction.
- It occurs in a single step with a backside attack by nucleophile.
- This causes inversion of configuration (Walden inversion).
- Rate depends on both substrate and nucleophile concentration.
- It is a second-order reaction.
Last verified on 19-05-2026
