CBSE Class 12 Chemistry Term-1 2021-22: 50 Important MCQ Questions With Solution

CBSE Class 12 Chemistry Term-1 2021-22:  50 Important MCQ Questions With Solution

In this post I have provided 50 important MCQs with answer key  for class 12 chemistry which are very important for coming board examination 2021-22. Each and every student must be practice these MCQs if they want to do good score in their chemistry examinations.

Given below are the 50 questions with four options and with answer key.

1. p-type semiconductors are formed When Si or Ge are doped with

(a) Group 14 elements

(b) Group 15 elements

(c) Group 13 elements

(d) Group 18 elements

Answer: (c) group 13 elements

2 Equimolar solutions in the same solvent have

(a) Same B.Ptbutdifferent F.Pt

(b) Same F. Pt, but different B.Pts.

(c) Same Boiling and same freezing point

(d) Different boiling and different freezing points.

Answer: (c) Same Boiling and same freezing point

3 Which of the following compounds has the highest boiling point?

(a)CH3CH2CH2Cl

(b) CH3CH2CH2CH2Cl

(c) CH3CH(CH3)CH2Cl

(d) (CH3)3CCl

Answer: (b) CH3CH2CH2CH2Cl

4 Acid catalysed dehydration of t-butanol is faster than that of n-butanol because

(a) tertiary carbocation is more stable than primary carbocation

(b) primary carbocation is more stable than tertiary carbocation

(c) t-butanol has a higher boiling point

(d) rearrangement takes place during dehydration of t- butanol

Answer: (a) tertiary carbocation is more stable than primary carbocation

5. Among the naturally occurring carbohydrates, furanose ring is found in the

(a) Glucose unit of cane sugar

(b) Glucose unit of cellulose

(c) Fructose unit of cane sugar

(d) Galactose unit of lactose

Answer: (c) Fructose unit of cane sugar

6. Fluorine differs from rest of the halogens in some of its properties. This is due to

(a) Its smaller size and high electronegativity.

(b) Lack of d-orbitals.

(c) Low bond dissociation energy.

(d) All of these.

Answer: (b) Lack of d-orbitals

7. The set with correct order of acidity is

(a) HClO < HClO2 < HClO3 < HClO4

(b) HClO4 < HClO3 < HClO2 < HClO

(c) HClO < HClO4 < HClO3 < HClO2

(d) HClO4 < HClO2 < HClO3 < HClO

Answer: (b) HClO4 < HClO3 < HClO2 < HClO

8. When chlorine reacts with cold and dilute solution of sodium hydroxide, it forms

(a) Cl and ClO

(b) Cl and ClO2

(c) Cl and ClO3

(d) Cl and ClO4

Answer: (a) Cl and ClO

9. The formation of O2+ [PtF6] is the basis for the formation of first xenon compound. This is because

(a) O2 and Xe have different sizes.

(b) Both O2 and Xe are gases.

(c) O2 and Xe have comparable electro-negativities.

(d) O2 and Xe have comparable ionisation enthalpies.

Answer: (d) O2 and Xe have comparable ionisation enthalpies

10 Globular proteins are present in

(a) Blood

(b) Eggs

(c) Milk

(d) All of these

Answer: (d) All of these

11. An alcohol X when treated with hot cone. H2SO4 gave an alkene Y with formula C4H8. This alkene on ozonolysis gives single product with molecular formula C2H4O. The alcohol is

(a) butan-1-ol,

(b) butan-2-ol

(c) 2-methylpropan-1-ol

(d) 2,2-dimethylbutynal-1-oI

Answer: (b) butan-2-ol

12 Arrange the following compounds in-decreasing order of their boiling points

(i) CH3Br

(ii) CH3CH2Br

(iii) CH3CH2CH2Br

(iv) CH2CH2CH2CH2Br

(a) (i) > (ii) > (iii) > (iv)

(b) (iv) > (iii) > (ii) > (i)

(c) (i) > (iii) > (ii) > (iv)

(d) (iii) > (iv) > (i) > (ii)

Answer: (b) (iv) > (iii) > (ii) > (i)

13 The vapour pressure of the two liquids ‘P’ and ‘Q’ are 80 and 60 torr respectively. The total vapour pressure of the solution obtained by mixing 3 mol of P and 2 mole of Q would be

(a) 68 torr

(b) 140 torr

(c) 72 torr

(d) 20 torr

Answer: (c) 72 torr

14 Which of the following conditions favours the existence of a substance in the solid state?

(a) High temperature

(b) Low temperature

(c) High thermal energy

(d) Weak cohesive forces

Answer: (b) Low temperature

15 How many lithium atoms are present in a unit cell with edge length 3.5 Å and density 0.53 g cm-3? (Atomic mass of Li = 6.94):

(a) 2

(b) 1

(c) 4

(d) 6

Answer: (a) 2

16 If an aqueous solution of glucose is allowed to freeze, then crystals of which substance will be separated and first?

(a) Glucose

(b) Water

(c) Both of these

(d) None of these

Answer: (b) Water

17 Alkyl halides are immiscible in water though they are polar because

(a) They react with water to give alcohols

(b) They cannot form hydrogen bonds with water

(c) C -X bond cannot be broken easily

(d) They are stable compounds and are not reactive

Answer: (b) They cannot form hydrogen bonds with water

18 Vapours of an alcohol X when passed over hot reduced copper, produce an alkene, the alcohol is

(a) primary alcohol

(b) secondary alcohol

(c) tertiary alcohol

(d) dihydric alcohol

Answer: (c) tertiary alcohol

19 Which one of the amino acids can be synthesised in the body?

(a) Alanine

(b) Lysine

(c) Valine

(d) Histidine

Answer: (a) Alanine

20. Partial hydrolysis of XeF4 gives

(a) XeO3

(b) XeOF2

(c) XeOF4

(d) XeF2

Answer: (b) XeOF2

21 Among the 15th group elements, as we move from nitrogen to bismuth, the pentavalency becomes less pronounced and trivalency becomes more pronounced due to

(a) Non-metallic character

(b) Inert pair effect

(c) High electronegativity

(d) Large ionization energy

Answer: (b) Inert pair effect

22. Collectively the elements of group 15 are called –

(a) Pnicogens

(b) Pnicopens

(c) Nicopen

(d) None of these

Answer: (a) Pnicogens

23. Which one of the following elements is most metallic?

(a) P

(b) As

(c) Sb

(d) Bi

Answer: (d) Bi

24. Which of the following is not true about amino acids?

(a) They are constituents of all proteins

(b) Alanine having one amino and one carboxylic group

(c) Most naturally occurring amino acids have D-configuration

(d) Glycine is the only naturally occuring amino acid which is optically inactive.

Answer: (c) Most naturally occurring amino acids have D-configuration

25. Picricacid is a yellow coloured compound. Its chemical name is

(a) m-nitrobenzoic acid

(b) 2, 4, 6-trinitropheriol

(c) 2, 4, 6-tribromophenol

(d) p-nitrophenol

Answer: (b) 2, 4, 6-trinitropheriol

26. Which of the following compounds will have the highest melting point?

(a) Chlorobenzene

(b) o-Dichlorobenzene

(c) m-Dichlorobenzene

(d) p-Dichlorobenzene

Answer: (d) p-Dichlorobenzene

27 Two solutions of a substance (non-electrolyte) are mixed in the following mariner: 480 mL of 1.5 M of first solution + 520 mL of 1.2 M second solution. What is the molarity of the final mixture?

(a) 1.20 M

(b) 1.50 M

(c) 1.344 M

(d) 2.70 M

Answer: (c) 1.344 M

28. Fe3O4 (magnetite) is an example of

(a) Normal spinel structure

(b) Inverse spinel structure

(c) Fluoride structure

(d) Anti fluorite structure

Answer: (b) inverse spinel structure

29. Which of the following crystals does not exhibit Frenkel defect?

(a) AgBr

(b) AgCl

(c) KBr

(d) ZnS

Answer: (c) KBr

30. If a is the degree of dissociation of Na2SO4 the Can’t Hoff factor (i) used for calculating the molecular mass is

(a) 1 + α

(b) 1 – α

(c) 1 + 2α

(d) 1 – 2α

Answer: (c) 1 + 2α

31. Ethyl alcohol is obtained when ethyl chloride is boiled with

(a) Alcoholic KOH

(b) Aqueous KOH

(c) Water

(d) Aqueous KMnO4

Answer: (b) Aqueous KOH

32. Ortho-nitrophenol is less soluble in water than, p- and m- nitrophenols because

(a) o-nitrophenol shows intramolecular H-bonding

(b) o-nitrophenol shows intermolecular H-bonding

(c) the melting point of o-nitrophenol is lower than those of m- and p-isomers

(d) o-nitrophenol is more volatile in steam than those of m- and p-isomers

Answer: (a) o-nitrophenol shows intramolecular H-bonding

33. Proteins are condensation polymers of

(a) α-amino acids

(b) β-amino acids

(c) α-hydroxy acids

(d) β-hydroxy acids

Answer: (a) α-amino acids

34. Which of the following statement is incorrect for group 15 elements?

(a) Order of ionization enthalpies is ΔiH1 < ΔiH2 < ΔiH3

(b) The boiling point and melting point increases from top to bottom in the group

(c) Dinitrogen is a gas while all others are solids

(d) All statements are correct

Answer: (b) melting point increase up to arsenic then decrease

35. Nitrogen is a relatively inactive element because

(a) Its atom has a stable electronic configuration

(b) It has a low atomic radius

(c) Its electronegativity is fairly high

(d) Dissociation energy of its molecule is fairly high

Answer: (d) Dissociation energy of its molecule is fairly high

36. In fibrous proteins, polypeptide chains are held together

(a) Van der waals forces

(b) Electrostatic forces of attraction

(c) Hydrogen bonds

(d) Covalent bonds

Answer: (c) Hydrogen bonds

37. Which compound can exist in a dipolar (zwitterion) structure?

(a) C6H5CH2CH (N = CH2) COOH

(b) (CH3)2 CHCH (NH2) COOH

(c) C6H5CONHCH2COOH

(d) HOOCCH2CH2COCOOH

Answer: (b) (CH3)2 CHCH (NH2) COOH

38. The best reagent to convert pent-3-en-2-ol into pent-3-en- 2-one is

(a) acidic permanganate

(b) acidic dichromate

(c) chromic anhydride in glacial acetic acid

(d) pyridiriium chlorochromate

Answer: (d) pyridiriium chlorochromate

39. Tertiary butyl alcohol gives tertiary butyl chloride on treatment with

(a) Conc HCl/anhydrous ZnCl3

(b) KCN

(c) NaOCl

(d) Cl2

Answer: (a) Conc HCl/anhydrous ZnCl3

40. Which of the following reactions will give the major and minor products?

(a) (a) is major product and (b) is minor product

(b) (a) is minor product and (b) is major product

(c) Both (a) and (b) are major products

(d) Only (b) is formed and (a) is not formed

Answer: (a) (a) is major product and (b) is minor product

41. Methyl bromide reacts with AgF to give methyl fluoride and silver bromide. This reaction is called

(a) Fitting reaction

(b) Swartz reaction

(c) Wurtz reaction

(d) Finkelstein reaction

Answer: (b) Swartz reaction

42. X is dissolved in water. Maximum boiling point is observed when X is ………… (0.1 M each)

(a) CuSO4

(b) BaCl2

(c) NaCl

(d) Urea

Answer: (b) BaCl2

43. The mole fraction of the solute in one molal aqueous solution is

(a) 0.027

(b) 0.036

(c) 0.018

(d) 0.019

Answer: (c) 0.018

44. NaCl type crystal (with coordination no. 6 : 6) can be converted into CsCl type crystal (with coordination no. 8 : 8) by applying

(a) High temperature

(b) High pressure

(c) High temperature and high pressure

(d) Low temperature and low pressure

Answer: (b) high pressure

45. In NaCl structure

(a) All octahedral and tetrahedral sites are occupied

(b) Only octahedral sites are occupied

(c) Only tetrahedral sites are occupied

(d) Neither octahedral nor tetrahedral sites are occupied

Answer: (b) only octahedral sites are occupied

46. What is the effect of Frenkel defect on the density of ionic solids?

(a) The density of the crystal increases

(b) The density of the crystal decreases

(c) The density of the crystal remains unchanged

(d) There is no relationship between density of a crystal and defect present in it

Answer: (c) The density of the crystal remains unchanged

47. To get n-type of semiconductor, germanium should be doped with

(a) Gallium

(b) Arsenic

(c) Aluminium

(d) Boron

Answer: (b) Arsenic

48. The atmospheric pollution is generally measured in the units of

(a) Mass percentage

(b) Volume percentage

(c) Volume fraction

(d) ppm

Answer: (d) ppm

49. A 5% solution of cane-sugar (molecular weight = 342) is isotonic with 1% solution of substance A. The molecular weight of X is

(a) 342

(b) 171.2

(c) 68.4

(d) 136.8

Answer: (c) 68.4

50. A mixture of 1-chloropropane and 2-chloropropane when treated with alcoholic KOH gives

(a) Prop-1-ene

(b) Prop-2-ene

(c) A mixture of prop-1 -ene and prop-2-ene

(d) Propanol

Answer: (a) Prop-1-ene

 

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