Kpk Chemistry 2023 — Solved MCQs

Question 1

Grignard's reagent contains_metal.

Accepted Answer

C. Mg — Grignard’s reagent contains the metal magnesium. It is typically represented as R-Mg-X, where R is an alkyl or aryl group, and X is a halide. The bond between the magnesium atom and the carbon atom of the R group is partially covalent and partially ionic. This unique bonding character is what gives Grignard reagents their strong nucleophilic reactivity.

Question 2

The bond angles of H-C-H and H-C-Cl bonds are

Accepted Answer

C. Equal to 109.5° — The bond angles of H-C-H and H-C-Cl in a molecule like methane (CH₄) or chloromethane (CH₃Cl) are predicted by the valence-shell electron-pair repulsion (VSEPR) model to be approximately 109.5°. This is because the carbon atom in these molecules is surrounded by four regions of high electron density, which arrange themselves in a tetrahedral geometry to minimize repulsion

Question 3

1,2,4,5-tetramethylbenzene is the IUPAC name of

Accepted Answer

C. Durene — The IUPAC name 1,2,4,5-tetramethylbenzene refers to an organic compound commonly known as Durene. It’s a colorless solid with a sweet odor and is classified as an alkylbenzene.

Question 4

Optical activity of a compound is measured by an instrument called

Accepted Answer

C. Polarimeter — The optical activity of a compound is measured by an instrument known as a polarimeter. This device measures the angle of rotation caused by passing linearly polarized light through an optically active substance.

Question 5

All of the given are alkanes except

Accepted Answer

D. C7H26 — C7H26 does not follow the alkane formula of ( CnH2n+2 ), so it is not an alkane.

Question 6

Oxa is the functional group of

Accepted Answer

D. Ether — The term “oxa” specifically refers to an oxygen atom that is part of an ether functional group, where the oxygen is bonded to two carbon-containing groups. The other three options—ketone, ester, and aldehyde—are incorrect because they have different structural features compared to ethers. In contrast, ethers have an oxygen atom single-bonded to two carbon-containing groups, without any double bonds to carbon, which is why “ether” is the correct answer.

Question 7

Which of the given is not organic in nature

Accepted Answer

B. NH4CNO — In summary:Methyl chloride and methanol are organic compounds.Ammonium isocyanate is inorganic.Urea is organic and contains nitrogen.

Question 8

The most stable oxidation state of manganese in acidic or neutral solution is

Accepted Answer

A. +2 — In acidic or neutral solutions, the most stable oxidation state of manganese is +2.

Question 9

Al₂O3 is.

Accepted Answer

D. Amhoteric oxide — Explanation will be added soon.

Question 10

Which of the given is NMR inactive nucleus?

Accepted Answer

D. O16 — O16 is NMR Inactive and has zero nuclear spin quantum number (I = 0). Remember that NMR-active nuclei provide valuable information about molecular structures and dynamics, while NMR-inactive nuclei do not contribute significantly to NMR spectra.

Question 11

In combustion analysis CO2 is absorbed by

Accepted Answer

B. KOH — In combustion analysis, carbon dioxide (CO2) is absorbed by a substance called (KOH). This process is an essential step in determining the composition of organic compounds. During combustion analysis, the unknown compound is burned in pure oxygen, and the resulting CO2 is captured by the KOH in absorber chamber. KOH acts as a CO2 absorber, allowing chemists to measure the carbon content of the sample.

Question 12

The height of the stratosphere is from

Accepted Answer

B. 10 to 50 km — The stratosphere, the second layer of Earth’s atmosphere, lies above the troposphere and below the mesosphere. The bottom of the stratosphere is approximately 10 kilometers above the ground at middle latitudes. The top of the stratosphere occurs at an altitude of 50 kilometers .

Question 13

Total number of chlorine atoms in DDT are:

Accepted Answer

C. 5 — DDT (Dichlorodiphenyltrichloroethane) has a chemical structure consisting of a central carbon backbone with multiple chlorine and hydrogen atoms attached. Its chemical formula is C14H9Cl5, indicating that it contains 14 carbon atoms, 9 hydrogen atoms, and 5 chlorine atoms. Therefore, the total number of chlorine atoms in DDT is 5.

Question 14

Proteins are polymers of

Accepted Answer

D. Amino acid — All proteins are polymers of amino acids, arranged in linear sequences.

Question 15

All are the derivatives of carboxylic acid except

Accepted Answer

C. Alkyl halide — Explanation will be added soon.

Question 16

Gem-Diol is the product of acid/base catalyzed reaction of water with

Accepted Answer

A. Aldehyde/ketone — Gem-diol, also known as hydrates, are formed when water reacts with aldehydes or ketones in the presence of an acid or a base catalyst.

Question 17

In Williamson's synthesis_ pair of reactants, react with each other to form ether.

Accepted Answer

B. R-OH and R-Mg - X — Williamson Ether Synthesis is a valuable method for creating ethers. It involves the nucleophilic displacement of a halide ion or another good leaving group by an alkoxide ion. Reactants:Alkyl Halide: A primary or secondary alkyl halide serves as the starting material. It can be an alkyl chloride, bromide, or iodide.Deprotonated Alcohol (Alkoxide Ion): This acts as the nucleophile. It is formed by treating an alcohol with a strong base (such as sodium ethoxide or potassium hydroxide).

Question 18

Lucas reagent is.

Accepted Answer

B. HCI and ZNCI2 — Zinc chloride ( ZnCl₂ ), when combined with concentrated hydrochloric acid, forms the Lucas reagent. This reagent is commonly used to test alcohols and classify them based on their reactivity.

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