Punjab Chemistry 2015 Paper 1 — Solved MCQs

Question 1

Which one is an incomplete period?

Accepted Answer

D. 7th — The period 7 is incomplete so far. It contains only two normal elements 87Fr and 88Ra, ten transition elements and fourteen inner transition elements. The inner transition elements of this period are called Actinides, as they follow 89Ac.The actinides are also shown at the bottom of the periodic table under the Lanthanides. Due to their scarcity, the inner transition elements are also called rare earth elements.

Question 2

The Oxides of Beryllium are:

Accepted Answer

C. amphoteric — The oxides of alkali and alkaline earth metals except beryllium are basic and contain O2- ions. The O2- ion has high affinity for proton and cannot exist alone in an aqueous solution. Therefore, it immediately takes proton from water and forms OH- ion. Oxides of relatively less electropositive elements, such as BeO, Al2O3 , Bi2O3 and ZnO are amphoteric and behave as acids towards strong bases and as bases towards strong acids.

Question 3

Which metal is used in thermite process because of its activity?

Accepted Answer

B. Aluminium — The metal typically used in the thermite process due to its high activity is aluminum (Al). In the thermite reaction, aluminum acts as the reducing agent, providing the necessary electrons to reduce another metal oxide, usually iron(III) oxide (Fe2O3), resulting in the production of elemental iron and aluminum oxide (Al2O3). This reaction is highly exothermic and is often used for welding and metallurgical purposes. The high reactivity of aluminum makes it suitable for this process.

Question 4

The most electronegative element of group V–A is:

Accepted Answer

A. N — Nitrogen has the highest electronegativity in group VA because the electronegative character decreases down the group.

Question 5

Alpha decay of the Radium gives:

Accepted Answer

D. Radon — Radon is the a-decay product of the radium. Radon is present to a very small extent in the atmosphere and it could be obtained as a by-product from the liquefaction of air.

Question 6

Which of the following is a typical transition metal?

Accepted Answer

C. Co — Group IIB elements (Zn, Cd and Hg) do not have a partially filled d-subshell either as elements or in any of their ionic state. Neither do they show typical properties of transition elements to any appreciable extent (except complex formation). Similarly, IIIB (Sc, Y and La) is another group of elements which do not show many of the properties associated with typical transition elements.

Question 7

Which one is the heterocyclic compound of oxygen?

Accepted Answer

C. Furan — The compounds in which the ring consists of atoms of more than one kind are called heterocyclic compounds or heterocycles. In heterocyclic compounds generally one or more atoms of elements such as nitrogen (Pyridine), oxygen (Furan) or sulphur (Thiophene) are present. The atom other than carbon viz, N, 0, or S, present in the ring is called a hetero atom.

Question 8

Preparation of vegetable ghee involves:

Accepted Answer

B. Hydrogenation — Hydrogenation of alkenes or alkynes in the presence of nickel at 200-300*C yields alkanes. The hydrogenation can also be carried out with platinum or palladium at room temperature but they are expensive than nickel. The method is of industrial importance. Production of vegetable ghee by the catalytic hydrogenation of vegetable oil (unsaturated fatty acids) is an example of the application of this method on industrial scale.

Question 9

Which compound is the most reactive one?

Accepted Answer

C. Ethene — The unreactivity of alkanes can also be explained on the basis of inertness of a s-bond. In a s -bond the electrons are very tightly held between the nuclei which makes it a very stable bond. A lot of energy is required to break it. A pi-bond is, therefore, a weak bond as compared to a s-bond. During a reaction it breaks comparatively easily rendering alkenes as reactive group of compounds. In alkynes, the carbon atoms are held together by a triple bond, a s-bond and two p-bonds. The electron density between the carbon atoms is very high which draws atoms very close to each other. Electrons in a triple bond are, therefore, less exposed and thus less reactive towards electrophilic reagents.Order of reactivity:Alkenes>ALkynes>Benzene>Alkanes

Question 10

Which one of the following is not a nucleophile?

Accepted Answer

B. BF3 — Nucleophile means nucleus loving. It has an unshared electron pair available for bonding and in most cases it is basic in character. It may be negatively charged or neutral.BF3 is electron deficient and hence is an electrophile.

Question 11

Which one is a dihydric alcohol?

Accepted Answer

D. Glycol — Alcohols are classified into monohydric and polyhydric alcohols. Monohydric alcohols contain one -OH group while polyhydric alcohols may contain two, three or more OH groups and named as dihydric or trihydric alcohols, etc. Glycol has two hydroxyl groups so it is dihydric alcohol.

Question 12

Which of the following will react with both aldehydes and ketones?

Accepted Answer

A. Grignard's reagent — Tollen's reagent, Benedict's reagent and Fehling's reagent react only with aldehydes whereas Grignard reagent reacts with both aldehydes and ketones to yield primary and secondary alcohols respectively.

Question 13

Ketones are prepared by the oxidation of:

Accepted Answer

B. Secondary alcohol — Primary alcohols on oxidation form aldehydes whereas secondary alcohols on oxidation form ketones. Tertiary alcohols are resistant towards oxidation and instead yield alkenes upon oxidation.

Question 14

Which of the following is not a fatty acid?

Accepted Answer

C. Phthalic acid — The aliphatic monocarboxylic acids are commonly called fatty acids because higher members of this series such as palmitic acid and stearic acid etc. are obtained by the hydrolysis of fats and oils. Phthalic acid is an aromatic carboxylic acid hence it is not classified as fatty acid.

Question 15

Which one is a disaccharide?

Accepted Answer

B. Sucrose — Glucose and fructose are monosaccharides. Starch and cellulose are polysaccharides.Sucrose is a disaccharide.

Question 16

Ammonium nitrate fertilizer is not used for which crop?

Accepted Answer

C. Paddy rice — It is a useful fertilizer for many crops except paddy rice because the microbial bacteria in flooded fields decomposes it to nitrogen gas. It is also used in combination with limestone. It is hygroscopic in nature.

Question 17

Which are carcinogenic class of compounds?

Accepted Answer

A. ﻿Dioxins — Dioxins are a group of highly toxic and persistent organic pollutants that can be formed as byproducts of various industrial processes, including waste incineration, chemical manufacturing, and certain combustion processes.

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