Punjab Chemistry 2017 Paper 3 — Solved MCQs

Question 1

Keeping in view the size of atoms.Which order is correct one?

Accepted Answer

A. Li>Na — They increase on moving from top to bottom in a group as the number of shells increases with the increase in atomic number. Hence, Lithium has a larger atomic radius than nitrogen because nitrogen has higher forces of interaction within its atom.

Question 2

The solution that flows out of cathode compartment of Nelson's cell contains NaOH:

Accepted Answer

A. 11% — Sodium ions combine with hydroxyl ions to form NaOH which is collected in the outer tank while hydrogen is drawn off through the outlet. From the above reactions, NaOH is formed at the cathode.

Question 3

The chief ore of Aluminium is:

Accepted Answer

A. Na3AlF6 — Aluminium is extracted from its chief ore, bauxite.

Question 4

The oxide of Nitrogen which causes hysterical laughter is:

Accepted Answer

B. N2O — Nitrous oxide, also known as dinitrogen oxide or dinitrogen monoxide, is a chemical compound with chemical formula N2O. It is commonly known as laughing gas due to the exhilarating effects of inhaling it.

Question 5

Which halogen is used in tooth paste?

Accepted Answer

A. F — Fluorine is used in the form of fluorides in drinking water and toothpaste because it reduces tooth decay by hardening the enamel on teeth.

Question 6

Which of the following metals is typical transition metal?

Accepted Answer

C. Fe — The elements below have properties that are typical of transition elements: chromium, Cr. manganese, Mn. iron, Fe.

Question 7

A saturated hydrocarbon containing five carbon atoms has isomers:

Accepted Answer

C. six — -pentane, which is a straight 5-carbon chain.Isopentane, which is a 4-carbon chain with a methyl group branching off the second C atom.Neopentane, which is a 3-carbon chain with two methyl groups branching off the central C atom.

Question 8

Which one is more reactive hydrocarbon?

Accepted Answer

B. H2C=CH2 — Ethyne is the most reactive among ethene , ethyne and benzene . ...Thus it possesses one sigma bond between two C-atoms and two pi bonds because a triple bond possesses multiple bonds and in multiple bond configuration one bond is a sigma bond and the rest bonds are pi .

Question 9

Resonance energy of benzene is:

Accepted Answer

C. 150.5 KJ/mole — The resonance energy of benzene is 36 kcal mol-1. To measure the resonance energy of benzene we start with the enthalpy of hydrogenation for cyclohexene, which is -28.6 kcal mol-1.

Question 10

Which of the followings is an electrophile?

Accepted Answer

D. BF3 — This strong partial positive character, coupled with a vacant orbital, makes BF3 a potent Lewis acid and thus an electrophile

Question 11

Rectified spirit contains about_ ethanol:

Accepted Answer

A. 95% — We have to remember that a rectified alcohol is highly concentrated ethanol which has been purified by means of repeated distillation, a process that is called rectification. Rectified spirit contains 95% ethanol with 5% water.

Question 12

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

Accepted Answer

D. Grignard's reagent — Both aldehydes and ketones react with Grignard reagent to give alcohols.

Question 13

Which of the following Amino acids is neutral in nature?

Accepted Answer

B. Glycine — Glycine is known for neutral amino acids. Glycine is hydrophilic in nature. It is one of the smallest molecules of the amino acid

Question 14

Which one of the following enzymes brings about hydrolysis of fats:

Accepted Answer

D. Lipase — Lipase is an enzyme that catalysts the hydrolysis of fat. Fat digestion mainly takes place in the small intestine with the help of lipase enzymes. Lipase enzyme is produced in small amounts by the mouth and stomach, and in larger amounts by the pancreas.

Question 15

Macro-nutrients are required by plants ranging:

Accepted Answer

D. 5-200 mg — Macronutrients are required in large amounts and normally constitute 1 000 mg kg –1 (0.1%) or more of the dry weight of the plant. Micronutrients are required in relatively small amounts and normally make up less than 500 mg kg –1 (0.05%) of the dry plant weight.

Question 16

Peroxyacetylnitrate(PAN) is an irritant to human beings and it effects:

Accepted Answer

A. eyes — PANs have many adverse effects in the human body such as reduced respiratory function (including emphysema and impaired breathing) and eye irritation. Human exposure to PANs typically occurs in urban centers where automobile and industrial emissions are high.

Question 17

To avoid the formation of toxic compounds with chlorine which substance is used for disinfection of water?

Accepted Answer

D. Chloramines — Most municipal drinking water treatment facilities now use chloramines instead of freely available chlorine to prevent the production of THMs. Ammonia is simply added to chlorine to create chloramines.

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