Punjab Chemistry 2017 Paper 2 — Solved MCQs

Question 1

The correct statement is :

Accepted Answer

A. Na+. is smaller than Na atom — Yes Na+ is smaller than Na because Na+ is formed when an electron is lost from the Na atom,Thus the effective nuclear charge increases bcz the number of protons exceeds the number of electrons . This results in bringing the valence shell a little closer to the nucleus because of a very strong nuclear pull.

Question 2

In the Down's Cell, CaCl2 is added to NaC! to:

Accepted Answer

D. lower its melting point — A small amount of calcium chloride is added to the sodium chloride to lower its melting point. The sodium chloride is melted electrically and kept molten by the current through the cell.

Question 3

The solution of the acid used for seasoning of food is:

Accepted Answer

C. Acetic acid — Acetic acid is used as a sour agent added in vinegar, pickled vegetables, and sauce, and as a raw material for spice.

Question 4

The benzene molecule contains:

Accepted Answer

D. Delocalized π-electron charge — Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon.

Question 5

For which mechanism, the first step involved is the same?

Accepted Answer

D. E1 and S,1 — E1: Leaving group departure followed by carbocation formation and deprotonation.S,1: Leaving group departure followed by nucleophilic attack.

Question 6

Hydrogen bond is the strongest between the molecules of

Accepted Answer

A. HF — As the name implies, one of the atoms must be hydrogen, therefore we are looking for it to be bonded to the atom with the greatest electronegativity, which is fluorine. Thus hydrogen fluoride, HF has the strongest individual hydrogen bonds between its molecules.

Question 7

A single chloride free radical can destroy how many ozone molecules?

Accepted Answer

B. 100000 — Free radicals have unpaired electrons. These are extremely reactive. As one chlorine free radical can remove 11000 ozone molecules from stratosphere.

Question 8

Laughing gas is chemically

Accepted Answer

B. N2O — Nitrous oxide is an oxide of nitrogen with a chemical formula N2O. This organic compound is colourless and non-flammable at room temperature. It is also known as nitrous or laughing gas. Joseph Priestley was the first to identify nitrous oxide in the year 1772

Question 9

Linear shape is associated with which type of hybridization.

Accepted Answer

A. sp — sp Hybridization can explain the linear structure in molecules. In it, the 2s orbital and one of the 2p orbitals hybridize to form two sp orbitals, each consisting of 50% s and 50% p character. The front lobes face away from each other and form a straight line leaving a 180° angle between the two orbitals

Question 10

Cannizzaro’s reaction is not given by

Accepted Answer

B. Acetaldehyde — The acetaldehyde (CH3CHO) has α−H atom, so does not give Cannizzaro reaction.

Question 11

Synthetic rubber is made by polymerization of

Accepted Answer

B. Chloroprene — Neoprene (also polychloroprene) is a family of synthetic rubbers that are produced by polymerization of chloroprene. Neoprene exhibits good chemical stability and maintains flexibility over a wide temperature range.

Question 12

Tincal is a mineral of

Accepted Answer

B. B — Tincal is a mineral version of the inorganic compound Borax that naturally occurs. Borax is a colourless, crystalline material that is soluble in water. It is most usually encountered in the form of tincal, which has the chemical formula - 10 H 2 O .

Question 13

Which one of these polymers is an addition polymer?

Accepted Answer

A. Nylon-6,6 — An addition polymer is a polymer that forms by simple linking of monomers without the co-generation of other products. Addition polymerization differs from condensation polymerization, which does co-generate a product, usually water. Neoprene, Teflon, Polyvinylchloride are examples of addition polymers.

Question 14

Which one is a non-typical transition element?

Accepted Answer

C. Zn — Zinc is not a transition metal because it forms only Zn2+ ions with all the 3d electrons present. Because Zn has 3d orbital fullfil by 10 electrons, they are paired. that's why they can't release this electrons only lose ns electron. SoZn is not transitional element.

Question 15

Methyl Alcohol is not used

Accepted Answer

A. As a solvent — Methanol is not a good solvent for extraction due to its toxicity and high solvent loss. Despite its versatility and use in various applications, the toxicity of methanol poses a risk to human health and the environment

Question 16

How many zones through which charge passes in a rotary kiln?

Accepted Answer

A. 04 — According to the temperature of the materials in the kiln, the cement rotary kiln system can be divided into: drying zone, preheating zone, decomposition zone, exothermic reaction zone, burning zone and cooling zone. The drying zone is a short part at the raw material entrance.

Question 17

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.

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