UAF ENTRY TEST PAST PAPER 16-07-2021 A
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چار آپشن میں سے کسی ایک پر کلک کرنے سے جواب سرخ ہو جائے گا۔
کن کے درمیان الڈول گاڑھاو ہوتا ہے؟
- Two ketones
- Two aldehydes
- A ketones and An aldehydes
- All of these
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Explanation
Aldol condensation can occur between two aldehydes, two ketones, or an aldehyde and a ketone if they have at least one α-hydrogen.
The reaction forms a β-hydroxy compound, which often dehydrates to an α,β-unsaturated product.
وہ گروپ جو الیکٹرو فیلک متبادل کے لئے بینزین رنگ کو غیر فعال کرتا ہے؟
- Chlorine
- Hydroxy
- Methyl
- None of these
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Explanation
Chlorine is an electron-withdrawing group due to its -I (inductive) effect, which deactivates the benzene ring toward electrophilic substitution.Despite this, it is ortho-para directing because of its lone pair involved in +R (resonance) effect.
الیکٹروفیلک متبادل میں مندرجہ ذیل میں سے کون سا کمپاؤنڈ بینزین سے آہستہ رد عمل کا اظہار کرتا ہے؟
- Phenol
- Nitro benzene
- Aniline
- None of these
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Explanation
Nitrobenzene reacts slower than benzene in electrophilic substitution due to the electron-withdrawing nitro group.
The NO₂ group deactivates the benzene ring, making it less reactive toward electrophiles.
ریڈیو ایکٹیویٹی کشی کی وجہ سے زمین پر کون سا نوبل گیس موجود ہے؟
- Ar
- Kr
- Rn
- None of these
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Explanation
Radon (Rn) is a radioactive noble gas that is formed naturally from the decay of uranium and thorium in the Earth’s crust.
It is colorless, odorless, and radioactive.
It is often found in soil and rock.
مندرجہ ذیل میں سے کس کا سب سے زیادہ پگھلنے کا مقام ہے؟
- Silicon
- Sulphur
- Phosphorus
- None of these
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Explanation
Silicon has the highest melting point among the given elements due to its giant covalent structure.
It requires more energy to break the strong covalent bonds.
ایس بلاک میں عناصر کی کل تعداد _____ ہے؟
- 14
- 24
- 12
- None of these
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Explanation
The S-block includes Group 1 (alkali metals) and Group 2 (alkaline earth metals) along with helium, totaling 14 elements.
These elements have their outermost electrons in the s-orbital.
Additional Information:
P-block → 6 groups (13–18) → 38 elements
D-block → Transition metals (Groups 3–12) → 40 elements
F-block → Lanthanides + Actinides → 28 elements
زیادہ تر عناصر _____ ہیں؟
- Metals
- Metalloids
- Non-metals
- None of these
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Explanation
Metals make up the majority of elements in the periodic table, especially on the left and center.
They are generally good conductors, malleable, ductile, and have high melting points.
الفا کے ذرات ______ کی طرح ہیں؟
- Helium atoms
- Helium nuclei
- Hydrogen atoms
- None of these
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Explanation
Alpha particles consist of 2 protons and 2 neutrons, making them identical to the nucleus of a helium atom (He²⁺).
They carry a +2 charge.
They are emitted during alpha decay in radioactive elements.
مادہ کے کرسٹل جعلی _____ میں درجہ بندی کی جاسکتی ہے؟
- Seven types
- Five types
- Six types
- None of these
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Explanation
Crystal lattices are classified into seven crystal systems based on their unit cell geometry.
These include:
- Cubic
- Tetragonal
- Orthorhombic
- Monoclinic
- Triclinic
- Hexagonal
- Rhombohedral (Trigonal)
پانی میں آکسیجن کی فیصد _____ ہے؟
- 8.8%
- 80%
- 88.8%
- None of these
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Explanation
Water (H₂O) is composed of 2 hydrogen atoms (1g each) and 1 oxygen atom (16g) → total molar mass = 18g.
Percentage of oxygen = (16/18) × 100 = 88.8% by mass.
