HBSE Class 12th Chemistry Solved Question Paper 2022
Q1. If the density of lake water is 1.25 g mL-¹ and contains 92 g of Na+ ions per kg of water. Calculate the molality of Na+ ions in lake.
Ans. Mass of Na+ ions = 92 g
Molar mass of Na+ ions = 23 g/mol or 23 g mol-¹
Number of moles of Na+ ions = 92g/23gmol-¹ = 4
Mass of water = 1 kg
Molality = (number of moles of sodium ions) ÷
Mass of water (in kg)
Molality= 4/1 = 4 M
Q2. Calculate the half life of a first order reaction from rate constant 200 sec-¹.
Ans. t½ = 0.693/k = 0.693/200 = 0.003465 second or 3.4 × 10-³ second
Q3. What is Gabriel Phthalimide synthesis reaction ?
Ans. The reaction of phthalimide with ethanolic KOH gives potassium salt of phthalimide. It is then heated with alkyl halide to form N-alkyl phthalimide. Alkaline hydrolysis (or treatment with hydrazine) gives a primary amine. Secondary or tertiary amines are not obtained as over alkylation is avoided. Aromatic primary amines cannot be prepared as aryl halides do not undergo nucleophilic substitution with anion formed by phthalimide.
Q4. Atoms of element B form hep lattice and those of the element A occupy 2/3 of tetrahedral voids. What is the compound formed by A and B ?
Ans. The number of tetrahedral voids formed is equal to twice the number of atoms of element B. But only 2/3 of these tetrahedral voids are occupied by atoms of element A. Therefore the ratio of number of atoms of A and B is 2x(2/3) : 1 = 4 : 3
The formula of compound is A4B3
Q5. 1.00 g of a non-electrolyte solute dissolved in 50 g of benzene lowered the freezing point of benzene by 0.40 K. The freezing point depression constant of benzene is 5.12 K kg mol-¹. Find the molar mass of the solute.
Ans. Here , given that kf = 5.12 K kg mol-¹
Mass of solvent, W1 = 50 g
Mass of solute, W2 = 1 g
∆Tf = 0.4 K
We need to find M2 , the molar mass of solute.
From the relation , we have
∆Tf = (kf×W2×1000) ÷ (W1×M2)
M2 = (kf×W2×1000) ÷ (W1×∆Tf)
= (5.12 x1×1000) ÷ (50×0.4)
=5120 ÷ 20 = 256 g
Molar mass of solute (M2) = 256 g
Q6. Explain giving reasons transition metals generally form coloured compounds.
Ans. Colour of transistion metal is due to the excitation of an electron from a lower energy d-orbital to a higher energy d orbital. The energy of excitation corresponds to the frequency of light absorbed and the colour observed corresponds to the complementary color of the light absorbed (whose frequency lies on the visible region).
The frequency of the light absorbed depends on the nature of the ligand. Transition metals form colored compounds due to the presence of vacant d-orbitals from the d-d transition of electrons which causes the color.
Q7. What happens when
(i) n-butyl chloride is treated with alcoholic KOH ?
Ans. When n- butyl chloride reacts with alcoholic KOH, the product formed is butene. This reaction is known as hydrohalogenation.
CH3–CH2–CH2–CH2–Cl + KOH(alc) Dehydration → CH3–CH2–CH2=CH2 + H2O
(ii) Bromobenzene is treated with Mg in the presence of dry ether?
Ans. The reaction of bromobenzene with Mg in the presence of dry ether, the product of this reaction is Phenylmagnesium bromide.
Ph–Br + Mg + dry ether → Ph–MgBr
(iii) Ethylbromide is treated with Na in the presence of dry ether?
Ans. Butane is formed when ethyl bromide is treated with sodium metal in dry ether. When sodium metals are reacted with alkyl bromides in the presence of dry ether, alkanes are produced. This reaction is called Wurtz reaction.
2C2H5Br + 2Na + dry ether → C4H10 + 2NaBr
Q8. Write the mechanism of acid dehydration of ethanol to yield ethene.
Ans. Step I : Protonation of oxygen atom of −OH group.
Step II : Loss of a molecule of water to form carbonium ion.
Step III : Deprotonation to form carbon carbon double bond.
Q9. A solution of Ni(NO3)2 is electrolysed between Platinum electrodes using a current of 5 amperes for 20 minutes. What mass of Ni is deposited at the Cathode ? (Ni^58.7)
Ans. Current, I = 5 amperes
Time = 20 × 60 = 1200 second
Charge = current × time = 5 × 1200 = 6000 C
According to the reaction,
Na²+(aq.) + 2e- → Ni(s)
Nickel deposit by (2×96487)C = 58.7 g
Nickel deposit by 6000 C = (58.7×6000) ÷ (2×96487) = 1.825 g
Hence 1.825g of nickel will be deposit at the cathode.
Q10. What are lyophilic and lyophobic sols ? Give one example of each type.
Ans. Lyophilic Sols– If dispersed phase (solid) tends to attract (i.e., like or love) dispersion medium (liquid), the resultant sol is termed as lyophilic sol. Examples : Sol of gum, gelatine, starch etc. are lyophilic sols.
Lyophobic Sols– On the other hand if dispersed phase tends to repel (i.e., dislike or hatred) dispersion medium, the resultant sol is termed as lyophobic sol. Examples : Sols of metals, metal hydroxides, metal sulphides etc. are lyophobic sols.
Q11.(a) Draw structure of 3-Hydroxy butanal.
(b) Describe Cannizzaro reaction.
Ans. Aldehydes which do not contain hydrogen when treated with a concentrated solution of an alkali undergo self oxidation-reduction. As a result, one molecule of aldehyde is reduced to corresponding alcohol while the other molecule is oxidized to the corresponding acid. This reaction is called Cannizzaro reaction.
(c) Describe Cross Aldol Condensation reaction.
Ans. When aldol condensation is carried out between two different aldehydes and or ketones, it is called cross aldol condensation. If both the reactants contain α-hydrogen atoms, it gives a mixture of four products. If both the reactants contain α-hydrogens, four compounds are obtained as products. For example, ethanal and propanal react to give four products.
(a) CH3COCH3 on reacting with the following will give what product ?
(i) NH2OH + CH3COCH3 →
Ans. CH3COOH + CH3NH2
(ii) HCN + CH3COCH3 →
(iii) NH2NHCONH2 + CH3COCH3 →
(b) Write the products of the following reactions :
Ans.(ii) C6H5CHO + HCl
Q12.(a) Give the reason for bleaching action of Cl2.
Ans. When chlorine reacts with water, it produces nascent oxygen. This nascent oxygen then combines with the coloured substances present in the organic matter to oxide them into colourless substances.
Cl2 + H2O → 2HCl + [O]
Coloured substances + [O] → Oxidized colourless substance
(b) What happens when SO2 is passed through an aqueous solution of Fe(Ill) salt ?
Ans. SO2 acts as a reducing agent when passed through an aqueous solution containing Fe(III) salt. It reduces Fe(III) to Fe(II) i.e., ferric ions to ferrous ions.
(c) Describe anomalous behaviour of Nitrogen.
Ans. Due to the small size of Nitrogen, it exhibits high ionization enthalpy, high electronegativity, and no d-orbitals. Nitrogen exists as a diatomic molecule as comprising of a triple bond whereas all the other elements of Group 15 exist as tetra-atomic molecules comprising a single bond.
(a) Write the order of thermal stability of hydrides of Group 16 elements.
Ans. The thermal stability of the hydrides of group 16 elements decreases down the group,
i.e. H2O > H2S > H2Se > H2Te > H2Po
This is because M-H bond dissociation energy decreases down the group with the increase in the size of central atom.
(b) Complete the following equations :
(i) PbS + 4O3 →
Ans. PbSO4 + 4O2
(ii) 8NH3(excess) + 3Cl2 →
Ans. N2 + 6NH4Cl
(iii) Zn + 4HNO3(conc.) →
Ans. Zn(NO3)2 + 2H2O + 2NO2
SET-A (Objective Questions)
Q1. Number of tetrahedral voids in the fcc unit cell is :
Q2. isotonic solutions are the solutions having same :
(B) Osmotic pressure
(C) Surface tension
Q3. For the given cell reaction Mg | Mg²+ || Cu²+ | Cu :
(A) Mg as cathode
(B) Cu as cathode
(C) Cu is oxidizing agent
(D) None of the above
Q4. Identify the order of reaction from given rate constant :
K = 2.6 x 10-⁴ L mol-¹ s-¹
(D) None of these
Q5. Which property of colloids is not dependent on charge on colloidal particles ?
(C) Tyndall effect
(D) None of these
Q6. Which of the following is strongest acid ?
Q7. Which of the following element does not show allotropy ?
Ans. (A) Nitrogen
Q8. Which element does not show variable oxidation state ?
Q9. Which of the following oxidation state is most common among the lanthanoids ?
Q10. What is the co-ordination number in the [Co(NH3)5(CO3)]CI compound ?
(C) 4(D) 2
For oxidation no of Co,
x + (5×0) + (-2) + (-1) = 0
x + 0 – 2 – 1 = 0
x – 3 = 0
x = 3
Q11. The oxidation number of Cobalt in K[Co(CO)4] is
For oxidation number of Cobalt,
1 + x + (4×0) = 0
1 + x = 0
x = -1
Q12. A primary alkyl halide would prefer to undergo :
(D) None of these
Q13. Molecular formula of ethers is :
Q14. Which is strongest acid in the following ?
Q15. lodoform test is not given by :
Q16. Hoffmann Bromamide degradation reaction form :
Q17. Which base is present in RNA but not in DNA ?
Q18. The Vitamin responsible for the coagulation of blood is :
(A) Vitamin C
(B) Vitamin D
(C) Vitamin B1
(D) Vitamin K
Q19. What is Frenkel defect ?
Ans. When some cations leave their normal lattice and occupy intertitial site.
Q20. Why gases less soluble in liquids as temperature is raised ?
Ans. Dissolution of gas is an exothermic process. As the temperature is raised, the equilibrium (⇌)shifts in reverse direction (Le-Chatelier’s principle). It results in decrease of solubility of gases in liquid.
Q21. What is strong electrolyte ?
Ans. A strong electrolyte is defined as a substance which dissociates almost completely into ions in aqueous solution and hence is a very good conductor of electricity. e.g. NaOH, KOH, HCI.
Q22. Define activation energy.
Ans. The minimum amount of energy needed to activate or energize molecules or atoms so that they can undergo a chemical reaction or transformation.
Q23. What is observed when a beam of light passed through a colloidal sol ?
Ans. Scattering of light (Tyndall effect)
Q24. What are ambidentate ligands ?
Ans. Ambidentate ligand is a type of ligand which can attach to the central metal atom through atoms of two different elements. More specifically ambidentate ligands have more than one donor atom but during coordinate bond formation only one of them attaches itself to the central metal atom.
Q25. What is Carbylamine Reaction ?
Ans. The carbylamine reaction, also known as Hofmann’s isocyanide test is a chemical test for the detection of primary amines. In this reaction, the analyte is heated with alcoholic potassium hydroxide and chloroform. If a primary amine is present, the isocyanide (carbylamine) is formed which are foul smelling substances.
Q26. What are the expected products of hydrolysis of lactose ?
Ans. β-D galactose and β-D glucose
Q27. Ionic solids conduct electricity in ……….. state.
Q28. Rate of reaction controlled by slowest step called …………
Ans. Rate Determining Step
Q29. The general electronic configuration of transition element is …………..
Q30. …………. ions produced from complex compound [Cu(NH3)4]SO4.
Q31. CH3CH2Br + Nal → ………… + NaBr
Q32. CH3CH2OH (ethanol) + H2SO4 + 443K → …………
Ans. CH2=CH2 (ethane)
Q33. ……….. is the IUPAC name of the compound CH3 – CH = CHCHO.
The common name for it is crotonaldehyde.
Q34. ………… is the IUPAC name of the complex compound K3[Al(C2O4)3].
Ans. Potassium Trioxalato Aluminate (III)
Q35. ………… is the deficiency disease of Vitamn C.
SET-B (Objective Questions)
Q1. The percentage of space unoccupied in BCC Unit cell is :
Ans. (B) 32%
Q2. Symbol for Cryoscopic constant is :
(D) None of these
Ans. (C) Kf
Q3. The SI Units of molar conductivity are :
(A) S m-¹ mol-1
(B) S m³ mol-¹
(C) S m-² mol
(D) S m² mol-¹
Ans. (D) S m² mol-¹
Q4. The units of rate constant for first order reaction is:
(A) Concentration² Time-²
(C) Concentration-¹ Time-¹
(D) Concentration Time-¹
Ans. (B) Time-¹
Q5. If rate of a reaction is independent of the concentration of reactants, then reaction is :
(A) Zero order
(B) First order
(C) Second order
(D) None of these
Ans. (A) Zero order
Q6. Which one is coloured ?
Ans. (A) [Ti(H2O)6]³+
Q7. Which type of Isomerism present in [Cr(NH3)5Cl]Br and [Cr(NH3)5Br]Cl ?
Ans. (D) ionic
Q8. In the following complexes which metal has zero oxidation number ?
Ans. (C) [Ni(CO)4]
Q9. In the following which is strongest Ligand ?
Ans. (C) CN-
Q10. Williamson synthesis is used to prepare :
Ans. (A) Ether
Q11. Which one is the strongest acid ?
Ans. (D) p-Nitrophenol
Q12. C2H5OC2H5 + HI → A + B, A and B are :
(A) C2H5OH, C2H5I
(B) C2H5OH, CH3I
(C) C2H5CHO, CH3I
(D) C2H5I, CH3OH
Ans. (A) C2H5OH, C2H5I
Q13. This reaction is :
(A) Etard reaction
(B) HVZ reaction
(C) Rosenmund reduction
(D) Gatterman reaction
Ans. (C) Rosenmund reduction
Q14. P is :
Ans. Option (A)
Q15. Aldehydes and Ketones can be distinguished by :
(A) Conc. H2SO4
(B) Anhyd. ZnCl2
(C) Tollens’ Reagent
(D) Conc. HCl
Ans. (C) Tollens’ Reagent
Q16. Reaction of Benzene diazonium chloride with ethanol will give :
Ans. (D) Phenol
Q17. Vitamin B1, is known as :
(A) Ascorbic acid
Ans. (B) Thiamine
Q18. Which vitamin is soluble in water ?
(A) Vitamin K
(B) Vitamin D
(C) Vitamin B
(D) Vitamin E
Ans. (C) Vitamin B
Q19. Which type of semiconductor is obtained when Silicon doped with Boron ?
Q20. What is the molality of pure water ?
Ans. 55.5 M
Q21. H2 + Br2 → 2HBr, For this Reaction Rate = K[H2][Br2]^½ . What is order of reaction ?
Q22. Smoke is which type of colloid ?
Q23. Among AsH3, NH3, PH3 and BiH3, which is strongest reducing agent ?
Q24. What is ZSM-5 ?
Ans. ZSM-5 which is a nanometer sized shape selective zeolite catalyst, is used as a highly effective isomerisation, polymerisation and a dehydration catalyst. It is used to convert methanol directly into gasoline (synthetic) along with a mixture of aromatic and aliphatic hydrocarbons on dehydrating. ZSM-5 is a zeolite which converts alcohol directly into gasoline (petrol).
Q25. In the following which is Dibasic acid ?
HClO4, H3PO3, H3PO2 and H3PO4
Q26. How many bases are present in DNA and RNA each ?
Q27. ionic solids have ……….. shape.
Q28. Chemical reaction Zn → Zn²+ + 2e- is an example of ………… process.
Q29. In Cr2O7²- , the oxidation number of Cr is ………….
Ans. x + (-14) = -2
x – 14 = -2
x = – 2 + 14 = 12
two chromium atoms have oxidation number +12.
one chromium atom has oxidation number 12/2 = +6.
Q30. …………. type of isomerism is present in [Cr(H2O)5CN]Cl2 and [Cr(H2O)5NC]Cl2.
Q31. Highest oxidation state shown by Mn is …………
Q32. Among Cl-, OH-, CO and NO2– only ………… is Ambidentate Ligand.
Q33. In CH3Br + KCN → A + LiAlH4 → B, here A and B are …………
Ans. A = CH3CN and B = CH3CH2NH2
Q34. Full name of ATP is ………….
Ans. Adenosine Triphosphate
Q35. Among C2H5I, C2H5Br, C2H5F and C2H5Cl, ………….. has minimum boiling point.
SET-C (Objective Questions)
Q1. In a face centred unit cell (FCC) the number of Octahedral Voids :
Ans. (A) 4
Q2. What is the value of Van’t Hoff factor (i) for K4[Fe(CN)6] ?
Ans. (B) 5
Q3. Standard Electrode potential for Standard Hydrogen Electrode (SHE) is :
(A) -0.5 V
(B) +1.0 V
(C) 0.0 V
(D) +2.0 V
Ans. (C) 0.0 V
Q4. Rate constant for a reaction is Rate = K[A]²[B]^-3/2 the order of reaction is :
Ans. (B) 0.5
2 + (-3/2) = 2 – 3/2 = 1/2 = 0.5
Q5. Dispersion medium in Aerosol Colloid is :
Ans. (A) Air
Q6. Which is most Basic ?
Ans. (C) NH3
Q7. Haber’s process is used to prepare :
Ans. (B) NH3
N2(g) + 3H2(g)⇌2NH3(g)
Q8. Which Element will show highest oxidation number ?
Ans. (B) Mn
Manganese shows the highest oxidation state +7.
Q9. Which is Ambidentate Ligand ?
Ans. (B) CN-
Q10. What is the magnetic moment of Sc³+ ion ?
(A) 1.73 BM
(B) 0 BM
(C) 5.92 BM
(D) 2.83 BM
Ans. (B) 0 BM
Magnetic moment (μ) = √n(n+2) = √0(0+2) = √0 = 0
Q11. The oxidation number of Cr in [Cr(NH3)4Cl2]Cl is :
Ans. (C) +3
x + (4×0) + (-1×2) = +1
x + 0 – 2 = +1
x = +1+2 = +3
Q12. What is the name of this reaction ?
ArN2 + X- + Cu/HCI → ArCl + N2 + CuX
(A) Coupling reaction
(B) Balz-Schiemann Reaction
(C) Gattermann reaction
(D) Sendmeyer reaction
Ans. (C) Gattermann reaction
Q13. Which has Highest Boiling point ?
Ans. (A) CH3CH2CH2CH2OH
Q14. Which one is Bidentate Ligand ?
Ans. (A) NH2CH2CH2NH2
Bidentate Ligands – When a ligand is bonded with two donor sites to the central metal atom/ion, it is called bidentate ligand, e.g. 1, 2-ethane diamine (en).
Q15. Which is Least Acidic ?
Ans. (A) C2H5OH
Q16. CH3CONH2 + Br2/KOH → P, P is :
Ans. (B) CH3NH2
Q17. Disaccharide is :
Ans. (C) Lactose
Q18. Enzymes are :
(A) Nucleic acids
Ans. (D) Proteins
Q19. What type of semiconductor formed when Si is doped with P ?
Q20. MnO4– → Mn+² for this reaction, how many Faraday are required ?
Q21. Is it possible that Molecularity of a reaction can be zero ?
Q22. Write IUPAC name of Zn2[Fe(CN)6].
Ans. Zinc Hexacynoferrate (II)
Q23. Among CH3CH2CH2CH2I and CH3CH2CH2CH2Cl will show SN² reaction fast.
Ans. CH3CH2CH2CH2I is faster as iodine is a better leaving group.
Q24. Write acidic order of Primary, Secondary and Tertiary alcohols.
Ans. Primary Alcohol (1°) > Secondary Alcohol (2°) > Tertiary Alcohol (3°)
Q25. Write its IUPAC name.
Q26. Write the names of two vitamins soluble in fats.
Ans. Vitamins A, D, E, K
Q27. Packing efficiency in BCC crystal is ………….. percent.
Q28. If 5g NaOH dissolved in 500 ml solution the molality of solution will be ………..
Ans. Molality = (5/40) ÷ (500/1000) = 5/40 × 1000/500 = 1/4 = 0.25 M
Q29. …………….. is the most Electronegative element in periodic table.
(Most Electopositive element in periodic table is Cesium)
Q30. If K = 0.693/t½ the order of reaction will be …………..
Ans. First Order
Q31. A catalyst ………….. the activation Energy.
32. P is :
33. Tollen’s reagent is …………..
Q34. Among (C2H5)2NH and C2H5NH2, …………… is more basic.
Q35. In RNA, the four basis present are Adenine, Guanine, Cytosine and ………….
SET-D (Objective Questions)
Q1. In a face centred unit cell (FCC) the number of Tetrahedral Voids :
Ans. (A) 8
Q2. Number of Faraday (F) required to reduce 1 mole of MnO4²- into Mn²+ :
Ans. (A) 5F
Q3. Identify the order of reaction from the given rate constant :
K = 1.6 x 10-⁶ L mol-¹ s-¹
(D) None of these
Ans. (C) Second
Q4. What is the value of Van’t Hoff factor (i) for dilute solution of Al2(SO4)3 ?
Ans. (C) 5
Q5. In which Bond Angle is maximum ?
Ans. (B) H2O
Q6. Adsorption is :
(A) Surface phenomenon
(B) Colligative property
(C) Oxidation process
(D) Reduction process
Ans. (A) Surface phenomenon
Q7. Number of Unpaired Electrons in Ni²+ are :
Ans. (B) 2
Q8. Which is the strongest acid ?
Ans. (A) HCIO4
Q9. Oxidation number of Pt in K2[PtCl6] is :
Ans. (C) +4
Q10. Which is Ambidentate Ligand ?
Ans. (A) NO2–
Q11. In the following which has Highest Boiling point ?
Ans. (B) CH3I
Q12. CH3CI + KCN → A + Na/C2H5OH → P, P is :
Ans. (B) CH3CH2NH2
Q13. What is the co-ordination number of Cr in [Cr(en)3]³+ complex ?
Ans. (C) 6
Q14. Which is the strongest acid ?
Ans. (D) FCH2COOH
Q15. What is the magnetic moment of [NiCl4]²- complex ?
(A) 2.82 BM
(B) 1.82 BM
(C) 5.92 BM
(D) 1.41 BM
Ans. (A) 2.82 BM
Q16. C2H5NH2 + CHCl3 + KOH + ∆ → P, P is :
Ans. (C) C2H5NC
Q17. Riboflavin is :
(A) Vitamin B
(B) Vitamin A
(C) Vitamin C
(D) Vitamin D
Ans. (A) Vitamin B
Q18. Which is not a carbohydrate ?
Ans. (C) Starch
Q19. Give one example of ionic Solid.
Ans. NaCl, KCl
Q20. Write units of specific conductance.
Ans. S/m or Siemen Per Meter
Q21. What is effect of temperature on rate of a reaction ?
Ans. Temperature ∝ Rate of reaction,
An increase in temperature typically increases the rate of reaction.
Q22. Write IUPAC name of [Pt(NH3)4NO2Cl]SO4.
Ans. tetramminechloronitroplatinum (IV) sulphate
Q23. Write chemical equation for a Wurtz reaction.
Ans. R–X + 2Na + X–R + Dry Ether → R–R + 2NaX
CH3–Br + 2Na + Br–CH3 + Dry Ether → CH3–CH3 + 2NaBr
Q24. What happens when formaldehyde reacted with conc. KOH solution ?
Ans. Formaldehyde when treated with KOH gives Methanol and Potassium Formate.
Q25. What is Denatured alcohol ?
Ans. Denatured alcohol is ethyl alcohol which has been made unfit for drinking purpose by adding poisonous substance like metanol, pyridine , copper sulphate etc. Ethanol is an important chemicalo. It is supplied at concessional rates to industries. It is therfore, made unfit for drinking purposes to prevent its misuse.
Q26. Write the name of two vitamins which are soluble in fat.
Ans. Vitamins A, D, E, K
Q27. …………. solids are electrical conductors, malleable and ductile.
Q28. Molal Elevation constant is also known as ……………
Ans. Ebullioscopic Constant
Q29. In SF6 hybridisation of Sulphur is …………
Q30. In the equation K = Ae^(-Ea/RT), Ea is …………….
Ans. Activation Energy
Q31. Among Cheese, Cloud, Smoke, ………….. is Gel.
Q32. IUPAC name is :
Q33. …………… type of Isomerism present in CH3CH2CHO and CH3COCH3.
Ans. Functional isomer
Q34. Primary, Secondary and Tertiary amines differentiated by …………….
Ans. Hinsberg Test
Q35. The disease caused by deficiency of Vitamin D is …………