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۔
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
اس سوال کو وضاحت کے ساتھ پڑھیں
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
اس سوال کو وضاحت کے ساتھ پڑھیں
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
اس سوال کو وضاحت کے ساتھ پڑھیں
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
اس سوال کو وضاحت کے ساتھ پڑھیں
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
کرومیم کی زمینی حالت میں الیکٹرانک ترتیب کیا ہے؟
- [Ar] 3d⁴ 4s²
- [Ar] 3d⁵ 4s¹
- [Ar] 3d⁶ 4s⁰
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Chromium (Cr) has atomic number 24.
- Expected configuration is [Ar] 3d⁴ 4s², but it is not stable.
- One 4s electron shifts to 3d to achieve stability.
- Half-filled d-subshell (3d⁵) is more stable due to symmetry and exchange energy.
- So chromium shows an exception in electronic configuration.
Last verified on 19-05-2026
بوران کی پہلی آئنائزیشن انرجی بیریلیم سے کم کیوں ہے۔ الیکٹران کس مدار سے نکلتا ہے؟
- 2p orbital
- 1s orbital
- 2s orbital
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Ionization energy is the energy needed to remove an electron from an atom.
- Beryllium (Be) has configuration: 1s² 2s² (stable 2s subshell).
- Boron (B) has configuration: 1s² 2s² 2p¹.
- The electron in boron is removed from a higher energy 2p orbital.
- 2p electron is farther and less tightly held than 2s, so easier to remove.
Last verified on 19-05-2026
آکسیجن کی مقناطیسی خصوصیات کس وجہ سے ہیں؟
- Unpaired electrons
- Paired electrons
- Ionic bonding
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Oxygen (O₂) shows a special magnetic behavior.
- It is attracted by a magnetic field (paramagnetic).
- This property comes from its electronic configuration.
- O₂ has two unpaired electrons in antibonding π orbitals*.
- Unpaired electrons create magnetic moment.
Last verified on 19-05-2026
کون سا مرکب سب سے زیادہ لیٹیس انرجی رکھتا ہے؟
- NaCl
- MgO
- KBr
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Lattice energy depends on the attraction between ions in an ionic solid.
- It increases with higher ionic charge and smaller ionic size.
- More charge and smaller ions → stronger electrostatic force.
- Among given options, MgO has Mg²⁺ and O²⁻ ions.
- This gives it the strongest attraction and highest lattice energy.
Last verified on 19-05-2026
- Tetrahedral
- Trigonal planar
- See-saw
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- SF₄ (Sulfur tetrafluoride) is a molecule of sulfur and fluorine.
- According to VSEPR theory, its shape depends on electron pairs around sulfur.
- Sulfur has 4 bonding pairs + 1 lone pair = 5 electron domains.
- This arrangement gives a see-saw molecular shape.
- Lone pair causes distortion from perfect symmetry.
Last verified on 19-05-2026
