Punjab Chemistry 2016 — Solved MCQs

Question 1

Ethanol can be converted into ethanoic acid by:

Accepted Answer

C. Oxidation — Oxidation of alcohols convert them into aldehydes and ketones. The best reagent for this purpose is acid dichromate. Further oxidation of these aldehydes/ketones yields carboxylic acids.

Question 2

Which reaction is disproportionate reaction?

Accepted Answer

B. Cannizzaro's reaction — Aldehydes that have no a -hydrogen atoms undergo Cannizzaro’s reaction. It is a disproportionation (self oxidation-reduction) reaction. Two molecules of the aldehyde are involved, one molecule being converted into the corresponding alcohol (the reduced product) and the other into the acid in the salt form (the oxidation product).

Question 3

Which test is called silver mirror test?

Accepted Answer

A. Tollen's test — Aldehydes form silver mirror with Tollen’s reagent (ammoniacal silver nitrate solution). Add Tollen’s reagent to an aldehyde solution in a test tube and warm. A silver mirror is formed on the inside of the test tube. High quality mirrors are manufactured by using this principle. Ketones do not give this test.

Question 4

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 5

Which of the following is mono-saccharide:

Accepted Answer

A. Fructose — Fructose is monosaccharide.Sucrose is a disaccharide that yields glucose and fructose on hydrolysis.Starch is a macromolecule or a polysaccharide. Cellulose is also a polysaccharide.

Question 6

Which three elements are needed for the healthy growth of plants?

Accepted Answer

C. N,P,K — The three elements most required by plants are nitrogen, phosphorous and potassium. Hence, fertilizers rich in these elements are utilised to boost plant growth.

Question 7

Ecosystem is a smaller unit of:

Accepted Answer

D. biosphere — Ecosystem is a smaller unit of biosphere which consists of community of organisms and their interaction with environment i.e., animals, plants and microorganisms which lie in a definite zone and depend on the physical factors such as soil, water, and air.

Question 8

Which is the longest period of periodic table?

Accepted Answer

C. 6 — The periods 4 and 5 are called long periods. Each long period consists of eighteen elements. The period 6 is the longest period, which contains thirty-two elements. The period 7 is incomplete so far. It contains only two normal elements Fr and Ra, ten transition elements and fourteen inner transition elements.

Question 9

The word alkali is derived from which language?

Accepted Answer

A. Arabic — The name alkali came from Arabic, which means ‘The Ashes’. The Arabs used this term for these metals because they found that the ashes of plants were composed chiefly of sodium and potassium.

Question 10

Which of the following is non metal?

Accepted Answer

A. B — Boron is the only non-metal in group IIIA. All other elements are considered metals. The small size and high nuclear charge make boron non-metallic while all the other elements of this group are metals.

Question 11

Which of the element gives acidic oxide?

Accepted Answer

A. N — Metal oxides are basic in character as they yield bases in water and non-metallic oxides are acidic because they form acids in water. There is a third type of oxides, which show both acidic and basic properties, these oxides are called amphoteric oxides. Hence, As, Sb and Bi give amphoteric oxides whereas Nitrogen being a non-metal gives acidic oxide.

Question 12

Which one of halogens is a liquid?

Accepted Answer

C. Bro — .Fluorine and chlorine are gases of pale yellow and greenish yellow colours respectively at room temperature and pressure. Bromine is a liquid of red-brown colour and iodine is a metallic-appearing shiny greyish black solid.

Question 13

Total number of d-block elements are:

Accepted Answer

D. 40 — Total number of d block elements is 40.

Question 14

A double bond consists of:

Accepted Answer

B. one sigma and one 2 —bond — A double bond consists of one sigma and one pi bond.

Question 15

Formula of Marsh gas is:

Accepted Answer

A. CH, 4 — Marsh gas, also known as methane, has the chemical formula CH4.

Question 16

Benzene cannot undergo:

Accepted Answer

D. elimination reactions — The highly stable, delocalized electrons of benzene ring are not readily available for the nucleophillic attack like the electrons of alkenes. Therefore, the electrons of benzene ring do not assist in the attack of weak electrophiles. Hence benzene undergoes:electrophilic substitutionoxidationadditionIt does not undergo elimination reactions.

Question 17

For which mechanisms, the first step is the same?

Accepted Answer

D. E1 and SN1 — In E1 mechanism, like SN1 mechanism, the first step is the slow ionization of the substrate to give a carbocation. In the second step, the nucleophile attacks on hydrogen to give an alkene as a product

Punjab Chemistry 2016 — Solved Past Paper with Answers

More Punjab / UHS Solved Papers