12th Class Chemistry Short Questions Preparation for Pakistani Students

Question # 1

What is the function of calcium in plant growth.

Ans 1: Function of calcium in plant growth:The presence of calcium is essential for the normal development of plants.The quantity of calcium required by different plants varies considerably.An adequate supply of calcium appears to stimulate the development of roots hairs and,infect,the entire root system.
Calcium is also necessary for the normal leave development and tends to accumulate in leaves as well as in bark,an adequate supply of calcium is also essential for the optimum activity of microorganisms that produce nitrates.The effect of calcium on the supply of available phosphorus in the soil is of special significance.Soils containing sufficient calcium are slightly alkaline in nature.

Question # 2

How digestion process is carried out in paper industry?

Ans 1: From wet digestion,the material is sent to digester ,The digester is usually 10 meters in length and 2 meters in diameter,It is made of steel and wrought iron,This is the main unit of process,The digestion process can be either batch or continuous.As the raw material enter into digester steam is introduced at the bottom and a liquor containing sodium sulphate is injected simultaneously to cover the raw material.

Question # 3

What is Newland's law of octaves?

Ans 1: Newland who was English chemist,in 1864,classified 62 elements,known at that time,in increasing order of their atomic masses.He noted that every eight element had some properties in common with the first one.The principle on which this classification is based was called the law of Octaves.

Question # 4

Define Primary Alkyl Halides and secondary alkyl Halides.

Ans 1: The alkyl halides in which halogen atom halogen atom is attached with carbon which is further atached to one or no carbon atom is called primary alkyl halide.
Secondry alkyl Halide:The alkyl halides in which halogen atom is attached with a carbon which is durther attached to two carbon atom is called secondry alkyl halide.

Question # 5

What is mil;k of Magnesia and for which treatment it used.

Ans 1: A suspension of Mg(OH)₂in water is called milk of magnesia and it is used for the treatment of acidity in stomach.

Question # 6

What are b-elimination reaction?

Ans 1: When nucleophile attacks on hydrogen atom attached to the beta carbon of the alkyl halide,we get an alkene ,such type of reaction are called elimination reaction .In E1 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.

Question # 7

Write name of following complexes:
1.K_{2 (}Cu(CN₄))

Ans 1: Names of K_{2 (}Cu(CN₄)) : Potassium tetracyanocuprate

Question # 8

Fehling solution reacts with aldehydes to give red ppt,Justify it?

Ans 1: Aliphatic aldehydes form a brick red precipitate with Fehling solution,To an aldehyde solution and Fehling solution and boil .A brick red precipitate of cuprous oxide id formed. Ketones do not give this test,.

Question # 9

Define nucleophilic addition reaction with an example?

Ans 1: Addition of nucleophillic reagent to the substrate in the presence of some catalyst is called nbucleophilic addition reaction.It is due to the unsymmetrical electronics configuration about the carbonyl group,the nucleophilic reagent can start the initial attack on the carbon.

Question # 10

What are ferons and Teflons?

Ans 1: Ferons: Fluorine is used for the preparation of freons,Freons is the commercial name of low molecular mass fluoro chloro carbons.These are being used as the refrigerants and aerosol propellants.
Teflons:Fluorine is used for the preparation of Teflon,It is polymerized tetrafluoroethylene compound.It is valuable plastic which resists the action of oxidants,acid and alkalies.

Question # 11

Which ester gives banana and orange smell?

Ans 1: Amylacetate gives banana while octyl acetate gives orange smell.

Question # 12

The elements of group VIII-A are called noble gases.Comment?

Ans 1: Elements of group VIII-A are called noble gases because,these elements are colourless,odourless monoatomic gases which are chemically un-reactive.

Question # 13

Define ecosystem.

Ans 1: Ecosystem is a similar unit of biosphere which consists of community of organisms and their zone and depend on physical factor such as soil water and air.

Question # 14

What is meant by Polypeptide and protein?

Ans 1: The formation of peptide bonds can continue until a molecule containing a several hundred thousand amino acid is formed,Such a molecule is called polyptide or protein.By convention a peptide having molecule is called a polypeptide which peptide having molecular mass more than 10,000 is called protein.

Question # 15

What are the following
1.Isoenzyme
2.Nucleotide

Ans 1: Isoenzyme:These are the enzymes from the same organisms which catalyze same reaction but are chemically and physically distinct from each other.
Nucleotide:Both DNA and RNA are formed by joining together a large number of Nucleotide units ,each of which is a nitrogenous base sugar phosphoric acid complex.

Question # 16

Mention four uses of ethene.

Ans 1: i) For the manufacture of polythene,a plastic material used of making toys,cables,bags,boxes etc.
Ans 2: ii) For a artificial ripening of the fruits.
Ans 3: iii) As a general anesthetic.
Ans 4: iv) For preparing Mustard gas a chemical used in Word War I,the name comes from its mustard like odour,it is not a gas,but a high boiling liquid that is dispersed as a mist of tiny droplest.

Question # 17

Define open chain compound.

Ans 1: Open chain may be branched or non branched .Open chain hydrocarbons are also called aliphatic compounds.
Branched chain compounds: Those organic compounds in which the carbon atom are attached on the side of the chain.

Question # 18

What are the primary pollutants?

Ans 1: The waste product given out from chimneys of industrial units and exhaust of automobiles may contain gases such as sulphur dioxide.sulphur trioxide,nitrogen oxides,carbon monoxide compound of fluorine and radioactive material .The waste products are called primary pollutants.

Question # 19

What do you know about reducing smog and oxidizing smog?

Ans 1: The smog contain high content of So₂it is chemically reducing in nature and is known as reducing smog,The main cause of reducing smog is combustion of coal.Photochemical smog consists of higher concentration of oxidants like ozone and is also termed as oxidizing smog,

Question # 20

How clinker is converted into cement?

Ans 1: The cement clinker are air cooled and groud with required of gypsum into fine powder.

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