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Kpk Chemistry 2011 — Solved Past Paper with Answers
All 17 MCQs from Kpk Chemistry 2011, solved with the correct answer highlighted and a full explanation for every question. This is a free MDCAT KPK / ETEA past paper — no signup, no ads. Practise it interactively in timed mode, drill more with free MDCAT MCQs, or browse all KPK / ETEA papers.
Attempt this paper interactively →Q1. Which one will have highest hydration energy?
- A. Na+
- B. Mg++
- C. Ca++
- D. AI++✓
Explanation: Explanation will be added soon:
Q2. Formula of plaster of paris is?
- A. 2CaSO4 2H2O
- B. 2CaSO4H2O
- C. CaSO4H2O
- D. 2CaSO4I/2H2O✓
Explanation: This formula might seem confusing, but it represents the correct concept if we simplify it. Each mole of CaSO4 is associated with half a mole of water, which is essentially {(CaSO4 \cdot \frac{1}{2} \text{H}_2 \text{O}). This correctly describes the hemihydrate form of calcium sulfate, known as plaster of Paris.
Why the other options are wrong
- A. This represents calcium sulfate dihydrate, commonly known as gypsum. This is not plaster of Paris.
- B. This formula suggests two moles of calcium sulfate combined with one mole of water. This does not correspond to any known compound and certainly not to plaster of Paris.
- C. This represents calcium sulfate hemihydrate, but with one mole of water per mole of calcium sulfate, which is incorrect for plaster of Paris.
Q3. Alkali metals?
- A. Are oxidixed by water
- B. Are reduced by hydrogen
- C. Are stored under water
- D. Form reactive cations✓
Explanation: Option D is correct. Alkali metals readily lose their single valence electron to form cations with a +1 charge, such as Na+ or K+. These cations are highly reactive due to the metals' low ionization energies and their tendency to achieve a stable noble gas electron configuration.
Why the other options are wrong
- A. This is true for alkali metals. When alkali metals react with water, they are indeed oxidized, forming hydroxides and releasing hydrogen gas. For example, the reaction of sodium with water can be represented as: [ 2Na+ 2H2O ---> 2NaOH + H2 ] While this statement is correct, it does not fully encompass the defining characteristic of alkali metals in comparison to option D.
- B. This is incorrect. Alkali metals are strong reducing agents themselves and are not reduced by hydrogen. Instead, they often react with hydrogen to form hydrides, such as lithium hydride (LiH), where the alkali metal is oxidized and hydrogen is reduced.
- C. This is incorrect. Alkali metals react vigorously with water, often producing heat and hydrogen gas, which can be explosive. Therefore, they are not stored under water but rather under oil or in an inert atmosphere to prevent such reactions.
Q4. Which one is monobasic acid?
- A. H2PO3
- B. H3BO3
- C. H3PO4✓
- D. H2SO4
Explanation: Explanation will be added soon:
Q5. Ostwald's process is used for the manufacturing of?
- A. N2O
- B. HNO3
- C. H3PO4
- D. NH3✓
Explanation: Ammonia (NH₃) is not manufactured by the Ostwald process but is actually a starting material for the process. The Ostwald process begins with the oxidation of ammonia to form nitric oxide, which is then further oxidized to nitrogen dioxide and then dissolved in water to form nitric acid, as outlined in the earlier explanation.
Why the other options are wrong
- A. Nitrous oxide (N₂O) is not produced by the Ostwald process. It is typically produced by the thermal decomposition of ammonium nitrate: [ NH₄NO₃ ---> N₂O + 2H₂O ] Therefore, option A is incorrect.
- B. Nitric acid (HNO₃) is actually produced by the Ostwald process, not used in its manufacturing. The Ostwald process converts ammonia (NH₃) into nitric acid (HNO₃) through a series of oxidation reactions, as explained earlier.
- C. Phosphoric acid (H₃PO₄) is not produced by the Ostwald process. It is usually produced by the reaction of sulfuric acid with phosphate rock: [ Ca₅(PO₄)₃F + 5H₂SO₄ + 10H₂O ---> 3H₃PO₄ + 5CaSO₄ \cdot 2H₂O + HF ] Therefore, option C is incorrect.
Q6. Ammonium nitrate on gentle heating produces?
- A. N2O
- B. N2
- C. NO
- D. N2O3✓
Explanation: The correct answer is D. N₂O₃ because, under gentle heating, ammonium nitrate can decompose to produce dinitrogen trioxide.
Why the other options are wrong
- A. While it's true that ammonium nitrate can decompose to produce nitrous oxide (N₂O), this typically occurs under more vigorous heating conditions, not gentle heating.
- B. Nitrogen gas (N₂) is a product of the decomposition of ammonium nitrate, but it's not the only product, and it's not typically the main product under gentle heating.
- C. Nitric oxide (NO) is not a product of the decomposition of ammonium nitrate under normal conditions. It's more likely to be produced from the decomposition of nitric acid or other nitrogen-containing compounds.
Q7. N2O when mixed with oxygen is used as?
- A. Explosive
- B. Refrigerant
- C. Catalyst
- D. Anaesthetic✓
Explanation: Nitrous oxide, when mixed with oxygen, has anaesthetic properties and is used in medical settings for its pain-reducing and sedative effects. It is commonly used in dentistry and minor surgeries as an anaesthetic agent.
Why the other options are wrong
- A. While nitrous oxide can support combustion and enhance the flammability of materials, it is not typically used as an explosive on its own. It is more commonly used as an oxidizer in combination with fuels for rocket propulsion.
- B. Nitrous oxide is not used as a refrigerant. Refrigerants are substances used in refrigeration cycles to transfer heat and cool spaces. Nitrous oxide is not suitable for this purpose.
- C. Nitrous oxide is not typically used as a catalyst. Catalysts are substances that increase the rate of a chemical reaction without being consumed in the process. Nitrous oxide does not exhibit this behavior in common applications.
Q8. The average percentage of availabe CI2 in bleaching powder is?
- A. 10%
- B. 20%
- C. 30%
- D. 40%✓
Explanation: The average percentage of available chlorine in bleaching powder is approximately 40%. This means that for every 100 grams of bleaching powder, about 40 grams are available chlorine, which is released as chlorine gas when needed for bleaching or disinfection purposes.
Why the other options are wrong
- A. 10% is too low for the average percentage of available chlorine in bleaching powder. Bleaching powder typically contains a much higher percentage of available chlorine.
- B. 20% is also too low for the average percentage of available chlorine in bleaching powder. The actual percentage is higher.
- C. 30% is still too low for the average percentage of available chlorine in bleaching powder. The correct percentage is higher.
Q9. Tel was used as:
- A. Refrigerant
- B. Antinock agent
- C. Bleaching agent
- D. Non stick✓
Explanation: Tel was used as a non-stick coating in cookware. It provided a slippery surface that prevented food from sticking, making it easier to cook and clean. However, it was later found to be toxic and has been replaced by other non-stick coatings.
Why the other options are wrong
- A. Tel was not used as a refrigerant. Refrigerants are substances used in refrigeration systems to transfer heat and cool spaces. Tel was not suitable for this purpose.
- B. Tel was not used as an antiknock agent in fuel. Antiknock agents are additives used in gasoline to reduce engine knocking and improve fuel efficiency. Tel was not used for this purpose.
- C. Tel was not used as a bleaching agent. Bleaching agents are substances used to whiten or remove color from materials. Tel was not known for its bleaching properties.
Q10. The process in which bigger molecules are broken into smaller one is:
- A. Polymerization
- B. Suifonation
- C. Cracking✓
- D. None of these
Explanation: Cracking is the correct answer. Cracking is a process used in refining petroleum to break down larger hydrocarbon molecules into smaller, more useful ones such as gasoline and diesel.
Why the other options are wrong
- A. This process involves the joining of smaller molecules to form a larger molecule. It is the opposite of what is described in the question, where bigger molecules are broken down into smaller ones.
- B. Sulfonation typically refers to the introduction of a sulfonic acid group into a molecule, not the breaking down of bigger molecules into smaller ones.
- D. This option is incorrect because cracking is the correct answer.
Q11. The hybridization of carbon in methane is:
- A. SP
- B. SP2
- C. SP3✓
- D. d2SP3
Explanation: Option C is correct. Methane has four equivalent C-H bonds and a tetrahedral geometry, which is achieved through SP3 hybridization of the carbon atom.
Why the other options are wrong
- A. This option is incorrect. Methane (CH4) has a tetrahedral geometry around the central carbon atom, which requires SP3 hybridization, not SP hybridization.
- B. This option is incorrect. SP2 hybridization is found in molecules like ethene (C2H4), which have trigonal planar geometry. Methane does not have this geometry.
- D. This option is incorrect. The "d" in d2SP3 implies the involvement of d orbitals, which is not necessary for the hybridization of carbon in methane. Carbon in methane only uses its 2s and 3p orbitals for hybridization, resulting in SP3 hybridization.
Q12. SN2 reaction completes in:
- A. Single step✓
- B. Two steps
- C. Three steps
- D. Four steps
Explanation: This option is correct. SN2 reactions occur in a single step where the nucleophile attacks the substrate and the leaving group leaves simultaneously, resulting in the substitution of the leaving group with the nucleophile.
Why the other options are wrong
- B. This option is incorrect for SN2 reactions. SN2 reactions proceed through a single step, as described above, rather than two separate steps.
- C. This option is incorrect for SN2 reactions. SN2 reactions are known for their simplicity and occur in a single step, unlike more complex reactions that might involve multiple steps.
- D. This option is incorrect for SN2 reactions. SN2 reactions are bimolecular, meaning they involve the collision of two molecules (the substrate and the nucleophile) in a single step, leading to the substitution reaction.
Q13. In the second subsistent occupies the....?
- A. Ortho position
- B. Para position
- C. Meto position
- D. Ortho para position✓
Explanation: This term is a bit ambiguous because "ortho" and "para" positions are distinct and do not usually occur together. However, it could be interpreted to mean that the substituents are located at both the ortho (positions 2 and 4) and para (positions 1 and 4) positions on the benzene ring.
Why the other options are wrong
- A. The ortho position refers to the positions on a benzene ring that are adjacent to a substituent. For example, in the case of a benzene ring with a single substituent, the ortho positions would be the positions directly next to the substituent.
- B. The para position refers to the position on a benzene ring that is opposite to a substituent. For example, in the case of a benzene ring with a single substituent, the para position would be the position directly across from the substituent.
- C. The meta position refers to the positions on a benzene ring that are two carbons away from a substituent. For example, in the case of a benzene ring with a single substituent, the meta positions would be the positions that are two carbons away from the substituent.
Q14. Reaction of alcohol with sodium produces?
- A. Alkoxides✓
- B. Ethane
- C. Ethene
- D. Aldehyde
Explanation: Option A is correct. When an alcohol reacts with sodium, it forms an alkoxide and hydrogen gas. Alkoxides are formed by the removal of a hydrogen atom from the alcohol molecule by the sodium metal.
Why the other options are wrong
- B. This option is incorrect. Ethane is not typically produced when alcohols react with sodium. The reaction of sodium with alcohols primarily leads to the formation of alkoxides and hydrogen gas, not ethane.
- C. This option is incorrect. Ethene is not produced when alcohols react with sodium. The reaction of sodium with alcohols does not involve the formation of carbon-carbon double bonds characteristic of ethene.
- D. This option is incorrect. Aldehydes are not typically produced when alcohols react with sodium. The reaction of sodium with alcohols does not involve the oxidation of the alcohol to form an aldehyde.
Q15. Which compound shows the higher boiling point?
- A. C2H6
- B. CH3CH2OCH2CH3
- C. C2H5Cl
- D. C2H5OH✓
Explanation: Ethanol is an alcohol with the formula C2H5OH. It is a polar molecule due to the presence of the hydroxyl (-OH) group, which results in hydrogen bonding between ethanol molecules. Hydrogen bonding is a strong intermolecular force, and compounds that exhibit hydrogen bonding tend to have higher boiling points compared to those that do not. Ethanol has the highest boiling point among the given options due to its ability to form hydrogen bonds.
Why the other options are wrong
- A. Ethane is a simple hydrocarbon with the formula C2H6. It is a nonpolar molecule, meaning it does not have a net dipole moment. The only intermolecular force present in ethane is London dispersion forces, which are relatively weak compared to other intermolecular forces. As a result, ethane has a relatively low boiling point.
- B. Diethyl ether is an ether with the formula CH3CH2OCH2CH3. Like ethane, it is a nonpolar molecule and exhibits only London dispersion forces as its intermolecular force. While it has a slightly higher molecular weight than ethane, its boiling point is still relatively low due to the weakness of London dispersion forces.
- C. Ethyl chloride is a molecule consisting of an ethyl group (C2H5) bonded to a chlorine atom (Cl). It is a polar molecule due to the electronegativity difference between carbon and chlorine. The predominant intermolecular force in ethyl chloride is dipole-dipole interactions. While stronger than London dispersion forces, dipole-dipole interactions are weaker than hydrogen bonding.
Q16. The percentage of nitroge in solid urea is......?
- A. 26
- B. 36
- C. 46✓
- D. 56
Explanation: Option C is correct. Urea has a nitrogen content of approximately 46% by weight.
Why the other options are wrong
- A. This option is incorrect. Urea has a higher percentage of nitrogen than 26%.
- B. This option is incorrect. Urea has a higher percentage of nitrogen than 36%.
- D. This option is incorrect. Urea does not have a nitrogen content as high as 56%.
Q17. Sources of SO2 in the atmosphere are:
- A. Sea sprays
- B. Households activities
- C. Fossil fuels✓
- D. Municipal wastes
Explanation: Fossil fuels, such as coal, oil, and natural gas, are the primary sources of sulfur dioxide (SO2) in the atmosphere. When these fuels are burned for energy production, sulfur compounds present in them are oxidized to form sulfur dioxide, which is released into the air. The combustion of fossil fuels in power plants, industrial facilities, and vehicles is a major contributor to sulfur dioxide emissions.
Why the other options are wrong
- A. Sea sprays are produced when waves break and release tiny water droplets into the air. While sea sprays can contain various substances, including salts and organic compounds, they are not significant sources of sulfur dioxide (SO2) in the atmosphere.
- B. Household activities can contribute to air pollution through the use of fossil fuels (e.g. heating and cooking with natural gas or oil) and the burning of waste. However, these activities are typically not major sources of sulfur dioxide in the atmosphere compared to industrial and transportation-related emissions.
- D. Municipal wastes, including solid waste from households and commercial establishments, can release sulfur dioxide when burned in incinerators. However, the contribution of municipal wastes to sulfur dioxide emissions is relatively small compared to other sources, such as fossil fuel combustion.
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