SPSC CHEMISTRY 25 YEARS PAST PAPERS
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چار آپشن میں سے کسی ایک پر کلک کرنے سے جواب سرخ ہو جائے گا۔
- Increases the average kinetic energy of the reactants
- Alters the reaction mechanism
- Increases the activation energy
- None of these
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Explanation
A catalyst provides an alternative reaction pathway with lower activation energy.It does not change reactants' energy but speeds up the reaction.
- Hydroxyl group
- Benzene ring
- Carbonyl group
- None of these
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Explanation
Phenols contain a hydroxyl (-OH) group attached to a benzene ring.They do not have a carbonyl group (C=O), which is found in aldehydes, ketones, and carboxylic acids.
الکحل اور کاربو آکسیلک ایسڈ کے مابین رد عمل کی پیداوار کو ______ کہا جاتا ہے؟
- Ester
- Amide
- Alkoxide
- None of these
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Explanation
The reaction between an alcohol and a carboxylic acid is called esterification.This reaction produces an ester and water as byproducts.
مصنوعی ذائقوں اور جوہر کی تیاری کے لئے مندرجہ ذیل میں سے کون سا کیمیکل استعمال کیا جاتا ہے؟
- Dimethyl ketone
- Methyl alcohol
- Ethyl acetate
- None of these
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Explanation
Ethyl acetate is widely used in the food industry for preparing artificial flavors and essences due to its fruity aroma.It is an ester formed from ethanol and acetic acid.It is commonly used in flavoring products like candies and beverages.
- 2 carbon atoms
- 2 hydrogen atoms
- 2 single bonds
- None of these
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Explanation
The formula CnH₂n+₂ represents alkanes, and adding +2 means two extra hydrogen atoms.This does not indicate additional carbon atoms or single bonds but an increase in hydrogen count.
- Most abundant organic compound
- Simplest organic compound
- The new organic compound
- None of these
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Explanation
Methane (CH₄) is the simplest hydrocarbon.It consists of one carbon atom bonded to four hydrogen atoms.It is the primary component of natural gas.It is widely used as a fuel source.Formula: CH₄IUPAC ID: MethaneSoluble in: Water, Methanol, Ethanol, Benzene, Acetone, Toluene, Diethyl etherMolar mass: 16.04 g/molBoiling point: -161.5 °CClassification: Hydrocarbon
ایک ایگزوتھرمک رد عمل کے لئے انفالپی کی علامت ______ ہوگی؟
- Positive
- Zero
- Negative
- None of these
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Explanation
In an exothermic reaction, heat is released, decreasing the system's enthalpy.This results in a negative enthalpy change (ΔH < 0).
- Similar
- Smaller
- Greater
- None of these
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Explanation
Entropy (S) is a measure of disorder or randomness in a system.Steam (gas) has higher entropy than ice (solid) because:- In steam, molecules move freely and randomly.
- In ice, molecules are tightly packed in an orderly structure.
Since gases have more molecular motion and disorder than solids, the entropy of steam is greater than that of ice.
عطارد کا پگھلنے کا نقطہ ______ ہے؟
- -39°C
- 0°C
- -100°C
- None of these
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Explanation
Mercury is a chemical element
It is commonly known as quicksilver.
It is the only metal to remain in liquid form at room temperature.
Droplets of liquid mercury are shiny and silver-white with a high surface tension, appearing rounded when on flat surfaces
Symbol: Hg
Atomic number: 80
Melting point: -38.83 °C
Boiling point: 356.7 °C
CAS ID: 7439-97-6
Atomic mass: 200.59 u
بنیادی الکحل کا ہلکا سا آکسیکرن ______ دیتا ہے؟
- An aldehyde
- A ketone
- An ether
- None of these
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Explanation
Primary alcohols oxidize to form aldehydes first.Further oxidation converts aldehydes into carboxylic acids.
