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Kpk Chemistry 2015 — Solved Past Paper with Answers
All 18 MCQs from Kpk Chemistry 2015, 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. 2,4,6 tribromo phenol formed by the reaction of phenol and Br2 has a color of?
- A. White✓
- B. Blue
- C. Red
- D. Yellow
Explanation: 2,4,6-tribromophenol, formed by the reaction of phenol and Br2, is a white solid. The presence of three bromine atoms on the phenol ring gives it a white color.
Why the other options are wrong
- B. The compound is not blue.
- C. The compound is not red.
- D. The compound is not yellow.
Q2. The hydrolysis of ester in the presence of an alkali (NaOH) is known as?
- A. Transesterification
- B. Saponification✓
- C. Decarboxyiation
- D. Esterification
Explanation: Saponification is the hydrolysis of an ester in the presence of an alkali, typically sodium hydroxide (NaOH) or potassium hydroxide (KOH). This reaction produces a carboxylate salt (soap) and an alcohol.
Why the other options are wrong
- A. Transesterification is the process of exchanging the organic group R'' of an ester with the organic group R' of an alcohol. It is not specifically the hydrolysis of an ester in the presence of an alkali.
- C. Decarboxylation is a chemical reaction that removes a carboxyl group from a chemical compound. It is not related to the hydrolysis of an ester.
- D. Esterification is the process of forming an ester from a carboxylic acid and an alcohol, typically in the presence of an acid catalyst. It is the reverse of saponification.
Q3. The optimum pH of pepsin is?
- A. 2.0✓
- B. 1.0
- C. 2.5
- D. 3.0
Explanation: Pepsin, a digestive enzyme found in the stomach, has an optimum pH of around 2.0. This acidic pH is necessary for the enzyme to function optimally in breaking down proteins into smaller peptides.
Why the other options are wrong
- B. While the stomach is highly acidic, with a pH around 1.0 to 2.0, the optimum pH for pepsin activity is closer to 2.0.
- C. The optimum pH for pepsin is slightly lower than 2.5, closer to 2.0, to effectively break down proteins.
- D. The optimum pH for pepsin is lower than 3.0, as it requires a more acidic environment to function optimally in protein digestion.
Q4. Depletion of ozone layer in stratosphere is caused by?
- A. SO2
- B. CO2
- C. CFC's✓
- D. CO
Explanation: CFC's are synthetic compounds that were widely used in refrigeration, air conditioning, and aerosol propellants. When released into the atmosphere, CFC's can reach the stratosphere, where they are broken down by ultraviolet (UV) light, releasing chlorine atoms. These chlorine atoms then catalytically break down ozone molecules, leading to ozone layer depletion.
Why the other options are wrong
- A. While sulfur dioxide can contribute to air pollution and acid rain, it is not a primary cause of ozone layer depletion.
- B. Carbon dioxide is a greenhouse gas that contributes to climate change but is not directly involved in ozone layer depletion.
- D. Carbon monoxide is a pollutant that can affect air quality and human health, but it is not a primary cause of ozone layer depletion.
Q5. The word alkali means:
- A. Base
- B. Basic salt
- C. Ashes✓
- D. Spirit
Explanation: The name alkali came from Arabic, which means ‘The Ashes’. Ashes typically refer to the residue left behind after burning or combustion of organic matter. The Arabs used this term for these metals because they found that the ashes of plants were com- posed chiefly of sodium and potassium. Alkali metals include the elements, lithium, sodium, potassium, rubidium, caesium and francium. These are very reactive metals, produce strong alkaline solutions with water.
Why the other options are wrong
- A. Alkali refers to a type of base, which is a substance that can accept protons (H+ ions) or donate electron pairs. Bases are known for their ability to neutralize acids and have a pH value greater than 7.
- B. While alkalis are related to bases, they are not the same as basic salts. Basic salts are formed by the partial neutralization of an acid by a base, resulting in a compound with both acidic and basic properties. Hence, this option is incorrect.
- D. Spirit refers to alcoholic beverages. It is not related to the term "alkali" in the context of chemistry.
Q6. Dehydration of alkyl halide is carried in the presence of _?
- A. H2SO4
- B. Alcoholic KOH
- C. Zn dust✓
- D. Aqueous KOH
Explanation: Dehydration of alkyl halides is carried out in the presence of zinc dust, which acts as a reducing agent. This reaction is often used to prepare alkenes from alkyl halides.
Why the other options are wrong
- A. Sulfuric acid is a strong acid and is typically used in other types of reactions, such as dehydration of alcohols to form alkenes, but it is not typically used in the dehydration of alkyl halides.
- B. Alcoholic KOH is often used in the elimination reactions of alkyl halides to form alkenes, but it is not typically used in the dehydration of alkyl halides.
- D. Aqueous KOH is typically used in nucleophilic substitution reactions of alkyl halides, not in the dehydration of alkyl halides.
Q7. All are meta directing groups except?
- A. -OR
- B. -CHO
- C. -CN✓
- D. -COOH
Explanation: The -CN group is a meta directing group in electrophilic aromatic substitution reactions. The electronegative nitrogen atom withdraws electron density from the ring, deactivating it toward electrophilic attack and directing substitution to the meta position.
Why the other options are wrong
- A. The -OR group is an ortho/para directing group in electrophilic aromatic substitution reactions. It can donate electron density through the oxygen atom, stabilizing the carbocation intermediate at the ortho and para positions.
- B. The -CHO group is also an ortho/para directing group. The carbonyl group can donate electron density to the ring through the oxygen atom, directing substitution to the ortho and para positions.
- D. The -COOH group is also a meta directing group. The carboxyl group is electron-withdrawing due to the presence of the carbonyl oxygen and the electronegative nature of the oxygen atom, directing substitution to the meta position.
Q8. The oxidation state of Cr in K2Cr2O7 is:
- A. +3
- B. +4
- C. +5
- D. +6✓
Explanation: As per standard, the oxidation number of potassium is +7 The oxidation number on Oxygen is -2 The oxidation number on Chromium = x Formal charge on K2Cr2O3 = 2 x oxidation number of K + 2 x oxidation number of Cr + 7 x oxidation number of oxygen 0 = 2 x 1 + 2 x x + 7 x -2 0 = 2 + 2x - 14 0 = 2x - 12 12= 2x 12/2 = x X = 6
Why the other options are wrong
- A. As per the solution, this option is incorrect.
- B. As per the solution, this option is incorrect.
- C. As per the solution, this option is incorrect.
Q9. Carboxylic acids have _ boiling points than the corresponding alcohols?
- A. Same
- B. Low
- C. High✓
- D. All of these
Explanation: Carboxylic acids have higher boiling points than the corresponding alcohols due to the presence of more extensive hydrogen bonding networks in carboxylic acids.
Why the other options are wrong
- A. Carboxylic acids generally have higher boiling points than the corresponding alcohols. This is due to the presence of hydrogen bonding in carboxylic acids, which is stronger than the intermolecular forces present in alcohols.
- B. Alcohols generally have lower boiling points than carboxylic acids. While both alcohol and carboxylic acid molecules can participate in hydrogen bonding, carboxylic acids have a more extended hydrogen bonding network due to the presence of two oxygen atoms (from the carbonyl and hydroxyl groups), leading to higher boiling points.
- D. Only option C (High) is correct. Carboxylic acids have higher boiling points than alcohols, and this difference is due to the presence of stronger intermolecular forces (hydrogen bonding) in carboxylic acids.
Q10. Which of the following is the strongest base?
- A. Al(OH)3
- B. Si(OH)4
- C. Mg(OH)2✓
- D. Be(OH)2
Explanation: Magnesium hydroxide, Mg(OH)2, is a strong base. It is used in antacids to neutralize excess stomach acid and is considered stronger than aluminum and silicon hydroxides.
Why the other options are wrong
- A. Al(OH)3 is aluminum hydroxide. It is an amphoteric compound, meaning it can act as both an acid and a base. However, it is not a strong base compared to the other options.
- B. Si(OH)4 is silicic acid. It is a weak acid rather than a base.
- D. Beryllium hydroxide, Be(OH)2, is a weak base. Beryllium compounds are generally not considered strong bases.
Q11. Which of the given is the quantitative chemical analysis?
- A. Titration✓
- B. Borox
- C. Flame test
- D. Salt Analysis
Explanation: Titration is a quantitative chemical analysis technique used to determine the concentration of a solution by reacting it with a standardized solution (titrant) of known concentration. The reaction is monitored using an indicator or a pH meter, and the volume of titrant required to reach the equivalence point is used to calculate the concentration of the analyte.
Why the other options are wrong
- B. Borox (borax) is a compound often used in chemical reactions and as a cleaning agent. However, it is not a technique for quantitative chemical analysis.
- C. The flame test is a qualitative analytical technique used to identify the presence of certain metal ions in a compound based on the characteristic colors they produce in a flame. It is not a quantitative analysis method.
- D. Salt analysis, also known as qualitative inorganic analysis, is a method used to determine the cations and anions present in a given salt. It is primarily a qualitative technique and is not typically used for quantitative analysis.
Q12. Which of the following given is acidic?
- A. CO2✓
- B. CO
- C. CaO
- D. Al2O3
Explanation: Carbon dioxide is acidic when dissolved in water, forming carbonic acid (H2CO3). This is due to the reaction of carbon dioxide with water to form carbonic acid, which can donate a proton (H+) and is therefore considered acidic.
Why the other options are wrong
- B. Carbon monoxide is not considered acidic. It does not readily donate a proton (H+) and does not exhibit acidic properties in the same way as carbon dioxide.
- C. Calcium oxide is a basic oxide, not an acidic one. It reacts with water to form calcium hydroxide, which is a strong base.
- D. Aluminum oxide is an amphoteric oxide, meaning it can act as both an acid and a base depending on the reaction conditions. However, it is not typically considered acidic in the same sense as carbon dioxide.
Q13. In Fehling Solution test, red ppt of oxide is?
- A. Cu✓
- B. CuO2
- C. Cu2O
- D. Cu2O2
Explanation: In the Fehling's solution test, a red precipitate of copper(I) oxide (Cu2O) is formed. This occurs when reducing sugars, such as glucose, are present in the solution being tested. The Cu2+ ions in Fehling's solution are reduced to Cu+ ions, which then react with hydroxide ions to form insoluble red copper(I) oxide.
Why the other options are wrong
- B. Copper(II) peroxide (CuO2) is not a common compound and is not typically formed in the Fehling's solution test. The correct red precipitate is copper(I) oxide (Cu2O).
- C. Cu2O (copper(I) oxide) is the correct red precipitate formed in the Fehling's solution test. It is a common indicator of the presence of reducing sugars.
- D. Copper(II) oxide (CuO) is not typically formed in the Fehling's solution test. The correct red precipitate is copper(I) oxide (Cu2O).
Q14. Which of the following can not be directly detected in an organic compound?
- A. Cl2
- B. N2
- C. O2✓
- D. S
Explanation: Oxygen gas (O2) cannot be directly detected in an organic compound because it is typically not a part of the organic compound's structure. Oxygen is often present in organic compounds as part of functional groups (e.g. hydroxyl groups), but it is not typically detected as O2 gas.
Why the other options are wrong
- A. Chlorine gas (Cl2) can be directly detected in an organic compound through various analytical techniques such as gas chromatography.
- B. Nitrogen gas (N2) can also be directly detected in an organic compound through techniques such as gas chromatography or mass spectrometry.
- D. Sulfur (S) can be directly detected in an organic compound through various analytical techniques such as elemental analysis or mass spectrometry.
Q15. Which of the following given is the condensation reaction?
- A. PVC
- B. Nylon✓
- C. Polythene
- D. None
Explanation: Nylon is formed by a condensation reaction between diamine and diacid monomers. In this reaction, water is eliminated as a byproduct.
Why the other options are wrong
- A. PVC is formed by polymerization, not condensation. Polymerization is a process where monomers join together to form a polymer without the formation of any byproducts.
- C. Polythene (polyethylene) is formed by polymerization of ethylene monomers, similar to PVC. It does not involve a condensation reaction.
- D. Nylon is an example of a condensation reaction in polymers. The other options involve polymerization reactions without the elimination of a small molecule like water, which is characteristic of condensation reactions.
Q16. Which one is found in rancid butter?
- A. C2H2O2
- B. C3H6O2✓
- C. H2O2
- D. C5H3O2
Explanation: Glycerol triacetate is a compound commonly found in rancid butter. It is a triglyceride that can undergo hydrolysis to form acetic acid and other compounds, contributing to the rancid odor of spoiled butter.
Why the other options are wrong
- A. Acetic acid is not typically found in rancid butter. Acetic acid is a common compound found in vinegar.
- C. Hydrogen peroxide is not typically found in rancid butter. It is a strong oxidizing agent commonly used as a disinfectant and bleaching agent.
- D. While unsaturated fatty acids are present in butter, the specific chemical formula given does not correspond to any known unsaturated fatty acid commonly found in rancid butter.
Q17. Which one is the strongest reducing agent?
- A. I-
- B. Br-
- C. Cl-✓
- D. F-
Explanation: Chloride ion is the strongest reducing agent among the options provided. It is lower in the reactivity series than bromide and iodide ions and can be easily oxidized to chlorine gas (Cl2), making it a stronger reducing agent.
Why the other options are wrong
- A. Iodide ion is a weaker reducing agent compared to chloride ion (Cl-). It is higher in the reactivity series and can be oxidized to iodine (I2), but it is not as strong a reducing agent as chloride ion.
- B. Bromide ion is also a weaker reducing agent compared to chloride ion. It is lower in the reactivity series than chloride ion and can be oxidized to bromine (Br2), but it is not as strong a reducing agent.
- D. Fluoride ion is the weakest reducing agent among the options provided. It is highest in the reactivity series and is not easily oxidized to fluorine gas (F2), making it a weak reducing agent.
Q18. Ethanol is produced from starch by the process of _?
- A. Decomposition
- B. Fermentation✓
- C. Hydrolysis
- D. Hydrogenation
Explanation: Ethanol is commonly produced from starch through fermentation. In this process, enzymes break down starch into sugars, which are then fermented by yeast to produce ethanol and carbon dioxide.
Why the other options are wrong
- A. Decomposition typically refers to the breakdown of compounds into simpler substances, often through chemical reactions. While ethanol can be produced from the decomposition of certain compounds, such as ethylene, this is not the process by which ethanol is typically produced from starch.
- C. Hydrolysis is a chemical process that involves the breakdown of a compound due to reaction with water. While hydrolysis can be used to break down starch into sugars, it is not the primary process used to produce ethanol from starch.
- D. Hydrogenation is a chemical process that involves the addition of hydrogen to a compound. It is not the process used to produce ethanol from starch.
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