SPSC 25 YEARS PAST PAPERS 2001 TO 2026
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چار آپشن میں سے کسی ایک پر کلک کرنے سے جواب سرخ ہو جائے گا۔
- H ----- F
- H ----- OH
- H ----- NH3
- None of these
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Explanation
The polarity of a bond is determined by the difference in electronegativity between the two atoms involved.Fluorine (F) is one of the most electronegative elements, much more so than hydrogen (H).It leading to a significant electron density shift towards fluorine, making the H ----- F bond highly polar.
- 512 liters
- 0.8 liter
- 800 liters
- None of these
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Explanation
To find the volume, we need to divide the mass by the density.Mass = 640g
Density = 0.8g/ml
First, convert the density to g/L by multiplying by 1000 (since 1L = 1000ml):
Density = 0.8g/ml × 1000 = 800g/L
Now, divide the mass by the density:
Volume = Mass ÷ Density
= 640g ÷ 800g/L
= 0.8 L
- Nitrogen-14
- Boron-14
- Oxygen-14
- None of these
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Explanation
Beta decay of carbon-14 involves the conversion of a neutron into a proton, emitting an electron (beta particle).This changes the atomic number from 6 (carbon) to 7 (nitrogen), forming nitrogen-14.
- 5
- 3
- 0
- None of these
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Explanation
In elemental form (N₂), nitrogen is in its natural, uncombined state.The oxidation number of any element in its pure form is always 0.
- 10
- 8
- 4
- None of these
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Explanation
For a strong acid with a high Ka value (10.8), it fully ionizes in water.pH is calculated as , and for a 1 M strong acid, , so pH = 4.
کیلشیم اور فاسفیٹ پر مشتمل پانی کو _____ کہا جاتا ہے؟
- Permanent hard water
- Permanent soft water
- Temporary hard water
- None of these
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Explanation
Temporary hard water contains dissolved calcium and magnesium bicarbonates, which can be removed by boiling.It differs from permanent hard water, which contains sulfates or chlorides that do not precipitate upon heating.
- CH3I
- CH3Br
- CH3Cl
- None of these
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Explanation
SN2 reactions favor weaker C-X bonds, and iodine (I) has the weakest bond due to its large atomic size.CH₃I reacts fastest because iodide is a better leaving group than Br, Cl, or F.
- Basic in nature
- Acidic in nature
- Natural compounds
- None of these
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Explanation
Phenols are weak acids due to the ability to donate a proton (H⁺).The phenoxide ion is stabilized by resonance, making phenols more acidic than alcohols.
- CN⁻
- NO
- O2
- None of these
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Explanation
Two species are isoelectronic if they have the same number of electrons.
N₂ has 14 electrons (7 from each nitrogen atom).
CN⁻ also has 14 electrons (6 from carbon, 7 from nitrogen, and 1 extra due to the negative charge).
کسی عنصر کی شناخت ______ کے ذریعہ طے کی جاتی ہے؟
- The number of its electron
- The number of its neutron
- The number of its proton
- None of these
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Explanation
The atomic number (number of protons) uniquely identifies an element.Changing the number of protons changes the element itself, while electrons and neutrons can vary.
