Kpk Chemistry 2021 — Solved MCQs

Question 1

Aldehydes or Ketones are reduced to alkanes in the presence of basic medium by.

Accepted Answer

B. Wolf kishner reduction — This method involves converting aldehydes and ketones to alkanes using hydrazine and a base. The reaction converts a carbonyl group to a methylene group.

Question 2

Which one of the given compounds will show Silver Mirror Test.

Accepted Answer

A. Ethanal — The Silver Mirror Test, also known as Tollens’ Test, is a used to distinguish between aldehydes and ketones. The test is generally given by compounds having an aldehydic group. This includes aldehydes, alpha-hydroxy ketones, and formic acid (its -COOH behaves like an aldehydic group).

Question 3

The more acidic compound among the given is:

Accepted Answer

D. CH3COOH — This is a carboxylic acid, which are generally more acidic due to the presence of a carboxyl group (-COOH).

Question 4

The dehydrating agent which is used in preparation of acetic anhydride from acetic acid at high temperature is.

Accepted Answer

B. H2SO4 — The most commonly used dehydrating agents for this reaction is concentrated sulphuric acid (H2SO4). These agents facilitate the removal of a water molecule from two molecules of acetic acid, resulting in the formation of acetic anhydride.

Question 5

Which one of the given is not a disaccharide?

Accepted Answer

C. Galactose — Among the sugars listed, galactose is not a disaccharide. It’s a monosaccharide, which is a single sugar unit. On the other hand, lactose, maltose, and sucrose are all disaccharides, which means they are each composed of two monosaccharide units:Lactose is composed of glucose and galactose.Maltose is composed of two glucose units.Sucrose is composed of glucose and fructose.

Question 6

The hydrolysis of triglycerides by alkalies is called

Accepted Answer

A. Saponification — The hydrolysis of triglycerides by alkalies is called saponification. This process involves the breakdown of a fat into glycerol and fatty acid salts, commonly known as ‘soap’. The reaction can be represented as follows: Fat/oil + Alkali → Soap + Glycerol

Question 7

Nylon (6,6) is the polymer of hexamethylene diamine and _.

Accepted Answer

C. Adipic acid — Nylon (6,6) is the polymer of hexamethylene diamine and adipic acid. These two compounds undergo a condensation polymerization to form Nylon (6,6), a type of polyamide.

Question 8

The temperature range of troposphere is:

Accepted Answer

D. 15°C to -56°C — The temperature in the troposphere ranges from an average of 15°C at sea level to about -57°C at the top.

Question 9

The spectroscopic technique which is used for determination of functional group in a compound is:

Accepted Answer

A. IR spectroscopy — The spectroscopic technique commonly used for the determination of functional groups in a compound is Infrared (IR) Spectroscopy. This technique is used in organic chemistry to detect the presence or absence of common functional groups. It provides detailed information about the infrared absorptions observed for various bonded atoms and groups.

Question 10

Those elements of group IV-A which have no tendency to form a dichloride arc.

Accepted Answer

A. C ans Si — Carbon and Silicon do not have a tendency to form dichlorides. This is because in their most stable oxidation state of +4, as seen in compounds like CCl4 and SiCl4, these compounds do not break down into dichlorides.

Question 11

The oxidation number of cobalt in [Co(NH3)4Cl2]Cl is.

Accepted Answer

C. 3 — The oxidation number of cobalt in [Co(NH3)4Cl2]Cl can be calculated by considering the charges of the individual ions and molecules in the complex.Ammonia (NH3) is a neutral ligand, so it does not contribute to the overall charge.Chloride ions (Cl-) each have a charge of -1.The complex ion [Co(NH3)4Cl2] has a charge of +1 (due to the extra Cl- outside the brackets). Therefore, the oxidation state of Co must balance the charges contributed by the two Cl- ions inside the brackets.Let’s denote the oxidation state of Co as "x". We can set up the following equation:x + 4(0) + 2(-1) = +1Solving for "x" gives:x = +1 + 2 = +3So, the oxidation number of cobalt in [Co(NH3)4Cl2]Cl is +3.

Question 12

The catalyst used for the conversion of SO₂ to SO3 in the manufacture of H2SO4 by contact process is.

Accepted Answer

B. V2O5 — The catalyst used for the conversion of sulfur dioxide (SO₂) to sulfur trioxide (SO₃) in the manufacture of sulfuric acid (H₂SO₄) by the contact process is vanadium pentoxide (V₂O₅). However, vanadium pentoxide is more commonly used due to its cost-effectiveness.

Question 13

Aromatic compounds are obtained upon fractional distillation of.

Accepted Answer

D. Coal tar — Aromatic compounds, which are a type of hydrocarbon, are primarily obtained from the fractional distillation of coal tar. Coal tar is a byproduct of the coking process where coal is heated in the absence of air to produce coke. This process also produces coal gas, which is used as a fuel.During the fractional distillation of coal tar, various components are separated based on their boiling points. Aromatic compounds, such as benzene, toluene, and naphthalene, are among these components and they have relatively high boiling points.

Question 14

The electrophile in the aromatic sulphonation reaction of benzene is:

Accepted Answer

D. SO3 — The electrophile in the aromatic sulphonation reaction of benzene is the sulphur trioxide (SO₃) molecule.In the sulphonation reaction, concentrated sulfuric acid (H₂SO₄) is used as a catalyst to generate the actual electrophile, sulphur trioxide. The reaction proceeds via an electrophilic aromatic substitution mechanism, where the sulphur trioxide molecule acts as the electrophile and attacks the aromatic benzene ring. This results in the substitution of a hydrogen atom on the benzene ring with a sulphonic acid group (-SO₃H), forming benzene sulphonic acid.

Question 15

A special type of functional group isomerism in which the isomers are in dynamic equilibrium with each other is called:

Accepted Answer

B. Tautomerism — The special type of functional group isomerism in which the isomers are in dynamic equilibrium with each other is called Tautomerism. Tautomers only differ in the position of the protons and electrons within the molecule while the carbon skeleton of the compound remains unchanged.

Question 16

A two step mechanism in which a carbocation is formed in first step and in second step an unsaturated compound is formed is _ mechanism.

Accepted Answer

C. E1 — The mechanism is known as the E1 mechanism, also known as unimolecular elimination. In this mechanism, there are usually two steps involved:Ionization: During this step, a carbocation is formed as an intermediate.Deprotonation: In this step, a proton is lost by the carbocation, resulting in the formation of an unsaturated compound.

Question 17

Grignard's reagent react with acetaldehyde to form addition products which upon acid hydrolysis yield _.

Accepted Answer

B. Secondary alcohol — If we use acetaldehyde (which is a form of aldehyde) in a reaction with a Grignard reagent, the exact type of alcohol that will be formed after acid hydrolysis is a secondary alcohol. This is because the Grignard reagent adds to the carbonyl carbon of the acetaldehyde, increasing the number of carbon atoms by one and resulting in a secondary alcohol. The general structure of the resulting alcohol would be R-CH(OH)-CH3, where R represents the alkyl or aryl group of the Grignard reagent.

Question 18

Picric acid is derivative of:

Accepted Answer

D. Phenol — Picric acid, also known as 2,4,6-trinitrophenol, is a derivative of phenol. It can be prepared by sulfonating phenol and then treating it with nitric acid.

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