HBSE Class 11th Chemistry Solved Question Paper 2021

HBSE Class 11th Chemistry Solved Question Paper 2021

HBSE Class 11 Chemistry Previous Year Question Paper with Answer. HBSE Board Solved Question Paper Class 11 Chemistry 2021. HBSE 11th Question Paper Download 2021. HBSE Class 11 Chemistry Paper Solution 2021. Haryana Board Class 11th Chemistry Question Paper 2021 Pdf Download with Answer.

Q1. Number of moles in 64 g of Oxygen are :

(A) 1.5

(B) 2.0

(D) 3.0

Ans. (B) 2.0

32gm = 1 mole

No. of moles = 64/32 = 2 moles

Q2. Find number of unpaired electrons in Nitrogen atom :

(A) 1

(B) 2

(D) 4

Ans. (C) 3

Q3. Arrange B, C, N, F and Si in correct order of their non-metallic character.

(A) B > C > Si > N > F

(B) Si > C > B > N > F

(D) F > N > C > Si > B

Ans. (C) F > N > C > B > Si

Q4. How many horizontal rows in Modern periodic table ?

(A) 2

(B) 6

(D) 8

Ans. (C) 7

Q5. Which compound shows zero dipole moment ?

(A) CCl4

(B) H2O

(D) H2S

Ans. (A) CCl4

Q6. Which type of intermolecular force exists in

(A) Dipole-dipole forces

(B) Dipole-induced dipole forces

(D) Hydrogen bond

Ans. (A) Dipole-dipole forces

Q7. A real gas acts as an ideal gas under which condition ?

(A) High temperature, low pressure

(B) Low temperature, high pressure

(D) Low temperature, low pressure

Ans. (A) High temperature, low pressure

Q8. The enthalpies of all elements in their standard states are :

(A) Unity

(B) Zero

(D) >0

Ans. (B) Zero

Q9. The pH of milk is :

(A) 7.4

(B) 9.2

(D) 6.8

Ans. (D) 6.8

Q10. The oxidation number of Mn in KMnO4 is :

(A) +1

(B) +5

(D) +3

Ans. (C) +7

1 + x + 4(-2) = 0

1 + x – 8 = 0

x = +7

Q11. The oxidation number of Nitrogen in NO3– is :

(A) −3

(B) +1

(D) +5

Ans. (D) +5

x + 3(-2) = -1

x – 6 = -1

x = +5

Q12. Which is heavy water ?

(A) H2O

(B) H2O2

(D) D2O2

Ans. (C) D2O

Q13. Which metal is used to prepare H2 with dil. H2SO4 ?

(A) Cu

(B) Hg

(D) Zn

Ans. (D) Zn

Q14. What is formula of Baking Soda ?

(A) NaHCO3

(B) Na2CO3

(D) KOH

Ans. (A) NaHCO3

Q15. Which alkali metal gives hydrated salt ?

(A) Li

(B) Na

(D) Cs

Ans. (A) Li

Q16. Thermodynamically the most stable form of Carbon is :

(A) Coal

(B) Graphites

(D) Diamond

Ans. (B) Graphites

Q17. CnH2n is general formula of :

(A) Alkene

(B) Alkane

(D) Arene

Ans. (A) Alkene

Q18. Heating a mixture of sodium benzoate with soda-lime gives :

(A) Methane

(B) Benzene

(D) Propane

Ans. (B) Benzene

Q19. Round up 10.4107 upto three significant figures.

Ans. 10.4

Q20. Which of the following species will have smallest size ?

Mg, Mg2+, Al, Al3+

Ans. Al³+

Mg > Al > Mg²+ > Al³+

Q21. Write general electronic configuration of S-block elements.

Ans. ns¹-²

Q22. What is Charle’s Law ?

Ans. Charles’s law states that if a given quantity of gas is held at a constant pressure, its volume is directly proportional to the absolute temperature.

V ∝ T (Pressure = Constant)

Q23. What is Constant in Boyle’s Law ?

Ans. The pressure and volume of a gas are inversely proportional to each other as long as the temperature and the quantity of gas are kept constant.

P ∝ 1/V (Temperature = Constant)

P1/P2 = V2/V1 = constant

Q24. What is reduction process ?

Ans. Reduction is the transfer of electrons between species in a chemical reaction where there is a process of gaining electrons or a decrease in the oxidation state by an element.

(Gain of Electron or Removal of Oxygen or Addition of Hydrogen)

Q25. Which is oxidizing agent in the following reaction ?

Zn + 2HCl → ZnCl2 + H2

Ans. HCl is oxidising agent.

Q26. Why are alkali metals not found in nature ?

Ans. Highly Reactive (so they make compound)

Q27. 1 milligram = ………. kilogram

Ans. 1/1000000 or 10-⁶

Q28. Binary compound formed by Mg and N is ……….

Ans. Mg3N2

Q29. Each line of V vs T graph at constant pressure is called ……….

Ans. isobar

Q30. In a reaction donor of electrons called …………

Ans. Nucleophiles or electron donor or Lone pair or Base

Q31. ………… number of coordinated bonded water molecules in CuSO4.5H2O.

Ans. Four

Q32. Group 15, 16, 17 hydrides called ………….

Ans. e-rich hydrides or Covalent hydride or Non-Metal hydride

Q33. ………… is oxidation state of Na in Na2O.

Ans.

2x + (-2) = 0

2x = 2

x = +1

Oxidation state of Na in Na2O is +1.

Q34. Group 2 Be, Mg, Ca, Sr, Ba are called …………… metals.

Ans. Alkaline Earth

Q35. The type of hybridization of carbon in graphite is …………..

Ans. sp²

Q36. Calculate the molarity of KOH in the solution prepared by dissolving its 5.6 g in water to form 250 mL of solution.

Ans. Weight of KOH (W) = 5.6g

Molecular weight of KOH (MW) = 56g

Volume of solution (V) = 250mL

Molarity (M) = W/MW × 1000/V = 5.6/56 × 1000/250 = 4/10 = 0.4 M

Q37. Calculate frequency of radiation having wavelength 5800 Å.

Ans. v = c/λ = (3×10⁸) ÷ (5800×10-¹⁰) = 5.172 × 10¹⁴ s-¹

Q38. What is enthalpy of Combustion ? Give one example.

Ans. Enthalpy of combustion of a substance is the change in enthalpy produced when one mole of the substance is completely burnt in air or oxygen at a given temperature. e.g.

C(s) + ½O2(g) → CO(g) ∆H = -110.5 kJ mol-¹

Q39. What will be the conjugate bases for the Bronsted acids HF and H2SO4 ?

Ans.

Conjugate Acid → Bronsted Base

HF → F-

H2SO4 → HSO4–

Q40. What are Nucleophiles ? Give its types with examples.

Ans. A nucleophile is a reactant which gives an electron pair to form a covalent bond. A nucleophile is usually charged negatively or is neutral with a lone couple of donatable electrons. e.g. H2O

Overall, the electron-rich species is a nucleophile.

Types– Negatively Charged Nucleophiles, All Lewis base which contains lone pairs, Ambident Nucleophile, Amphiphile Nucleophile

Q41. Explain Pauli Exclusion principle with example.

Ans. The Pauli exclusion principle states that in a single atom no two electrons will have an identical set or the same quantum numbers (n, l, ml, and ms). To put it in simple terms, every electron should have or be in its own unique state (singlet state). e.g.

Q42. Define open system, extensive properties and enthalpy.

Ans. Open system– The system which allows the exchange of both matter and energy with the surroundings is called an open system.

Extensive properties– The properties which depend upon the quantity of matter or substance present in the system. For example: number of moles, mass, volume etc.

Enthalpy– The heat absorbed or released during a process at constant pressure is equal to the change in enthalpy. Sometimes referred to as “heat content,” enthalpy is a fascinating and uncommon word that most people prefer to use.

Q43. Define acid and base with example in Arrhenius concept.

Ans. Acid– Acid are those substances which release H+ ions when dissolved in water. e.g. HCL, HNO3

Base– Bases are those substances which release OH− ions when dissolved in water. e.g. NaOH, KOH

Q44. What do you understand by the following ?

(a) inert pair effect

Ans. On moving down the group, the tendency of s electrons to participate in chemical bonding decreases. This effect is called inert pair effect. Due to this, in group 13, the stability of +3 oxidation state decreases and the stability of +1 oxidation state increases.

(b) allotropy

Ans. Allotropy is the phenomenon in which an element exist in more than one form having same chemical properties by different physical properties. For example, diamond, graphite and fullerenes are allotropes of carbon.

Ans. Atoms of carbon and some other elements link with one another through strong covalent bonds to form long chains or branches. This is called catenation. Usually, it is shown by C, S and Si.

Q45. Give IUPAC names of the following :

Ans.

(a) 3-methyl pentane nitrile

(b) 3-methyl butanoic acid

Q46. What is meant by the term Bond Order ? Calculate the bond order of N2, O2, O2+ and O2-.

Ans. Bond order– The number of chemical bonds present between two atoms of a molecule or one half of the difference between the number of electrons present in the bonding and anti-bonding orbitals of a molecule.

Bond order of N2 = (10-4)/2 = 6/2 = 3

Bond order of O2 = (10-6)/2 = 4/2 = 2

Bond order of O2+ = (9-6)/2 = 3/2 = 1.5

Bond order of O2– = (10-7)/2 = 3/2 = 1.5

What is meant by hybridization of atomic orbitals ? Describe the shapes of sp, sp² and sp³ hybrid orbitals with example.

Ans. Hybridization is defined as an intermixing of a set of atomic orbitals of slightly different energies, thereby forming a new set of orbitals having equivalent energies and shapes.

For example, one 2s-orbital hybridizes with two 2p-orbitals of carbon to form three new sp² hybrid orbitals.

These hybrid orbitals have minimum repulsion between their electron pairs and thus, are more stable. Hybridization helps indicate the geometry of the molecule.

Shape of sp hybrid orbitals– sp hybrid orbitals have a linear shape. They are formed by the intermixing of s and p orbitals as :

Shape of sp² hybrid orbitals– sp² hybrid orbitals are formed as a result of the intermixing of one s-orbital and two 2p-orbitals. The hybrid orbitals are oriented in a trigonal planar arrangement as:

Shape of sp³ hybrid orbitals– Four sp³ hybrid orbitals are formed by intermixing one s-orbital with three p-orbitals. The four sp3 hybrid orbitals are arranged in the form of a tetrahedron as :

Q47(i) What is Friedel-Crafts alkylation reaction ?

Ans. Friedel-Crafts Alkylation refers to the replacement of an aromatic proton with an alkyl group. This is done through an electrophilic attack on the aromatic ring with the help of a carbocation. The Friedel-Crafts alkylation reaction is a method of generating alkylbenzenes by using alkyl halides as reactants.

(ii) What is Markovnikov’s rule ? Explain with example.

Ans. When an unsymmetrical reagent is added to an unsymmetrical alkene, the negative part of the reagent is attached to the unsaturated C atom having less number of hydrogen atoms. Thus, when HBr is added to propene, isopropyl bromide is obtained as major product.

CH3−CH=CH2 + HBr → CH3−CH(Br)–CH3

(i) What is Wurtz reaction ?

Ans. Wurtz’s reaction is an organic chemical coupling reaction wherein sodium metal is reacted with two alkyl halides in the environment provided by a solution of dry ether in order to form a higher alkane along with a compound containing sodium and the halogen.

R–X + 2Na + X–R → R–R + 2Na–X (Basic reaction)

R = alkyl group, X = halogen (F, Cl, Br, I)

(ii) What is anti-Markovnikov’s rule ? Explain with example.

CH3−CH=CH2 + HBr → CH3−CH(H)–CH2(Br)

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