You all know that CBSE Board Exam is coming in February. So, I have brought CBSE Board Class 12 Chemistry Important Questions 2024 which are being asked the same for last 3-4 years. Try to solve these questions for securing high marks in your board examination.
You can also check the Important Questions for Hindi, English and Other Subjects.
CBSE Board Class 12 Chemistry Important Questions 2024: Objective
1. Toluene reacts with a halogen in the presence of iron (III) chloride giving ortho and para halo compounds. The reaction is
(a) Electrophilic elimination reaction
(b) Electrophilic substitution reaction
(c) Free radical addition reaction
(d) Nucleophilic substitution reaction
2. Which reagent will you use for the following reaction? CH3CH2CH2CH3 CH3CH2CH2CH2Cl + CH3CH2CHCICH3
(a) Cl2/UV light
(b) NaCl + H2SO4
(c) C12 gas in dark
(d) Cl2 gas in the presence of iron in dark
3. The position of -Br in the compound in CH3CH=CHC(Br)(CH3)2 can be classified as
(a) Allyl
(b) Aryl
(c) Vinyl
(d) Secondary
4. Chlorobenzene is formed by reaction of chlorine with benzene in the presence of AlCl3. Which of the following species attacks the benzene ring in this reaction?
(a) Cl-
(b) Cl+
(c) AlCl3
(d) [AICI4]-
5. Alkyl halides undergoing nucleophilic bimolecular substitution involve.
(a) Retention of configuration
(b) Racemic mixture
(C) Inversion of configuration
(d) Formation of carbocation
6. Polar solvents make the reaction faster as they:
(a) Destabilize transition state and decrease the activation energy.
(b) Destabilize transition state and increase the activation energy.
(c) Stabilize transition state and increase the activation energy.
(d) Stabilize transition state and decrease the activation energy.
7. Reaction of C6H5CH2Br with aqueous sodium hydroxide follows
(a) Sn1 mechanism
(b) Sn2 mechanism
(c) Any of the above two depending upon the temperature of reaction
(d) Saytzeff rule
8. Arrange the following compounds in increasing order of boiling point: Propan-1-01, butan-1-01, butan-2-01, pentan-ol
(a) Propan-1-01, butan-2-o1, butan-1-01, pentan-01
(b) Propan-1-01, butan-1-01, butan-2-01, pentan-1-01
(c) Pentan-1-01, butan-2-o1, butan-1-01, propan-1-01
(d) Pentan-1-01, butan-1-ol, butan-2-01, propan-1-01
9. What will be the rate equation for the reaction 2X + Y → Z, if the order of the reaction is zero?
(a) Rate = k[X][Y]
(b) Rate = k
(c) Rate = k[X]0[Y]
(d) Rate = k[X][Y]0
10. . If limiting molar conductivity of Ca2+ and Clare 119.0 and 76.3 S cm2 mol-1, then the value of limiting molar conductivity of CaCl2 will be
(a) 195.3 S cm2 mol-1
(b) 271.6 S cm2 mol-1
(c) 43.3 S cm2 mol-1
(d) 314.3 S cm2 Mol-1
11. The helical structure of protein is stabilized by:
(a) Peptide bond
(b) Dipeptide bond
(c) Hydrogen bonds
(d) Vander Waal’s forces
12. The term homogenous mixtures signifies that
(a) Its composition is uniform throughout the mixture.
(b) Its properties are uniform throughout the mixture.
(c) Both composition and properties are uniform throughout the mixture.
(d) Neither composition nor properties are uniform throughout the mixture.
13. For a reaction nx yz the rate of reaction becomes twenty seven times when the concentration of X is increased three times. What is the order of the reaction?
(a) 2
(b) 1
(c) 3
(d) 0
14. The overall rate of a complex reaction is governed by
(a) the rate of fastest intermediate step
(b) the sum total of the rates of all intermediate steps
(c) the average of the rates of all the intermediate steps
(d) the rate of slowest intermediate step
15. A reaction is found to be of second order with respect to concentration of carbon monoxide. If concentration of carbon monoxide is doubled, the rate of reaction will
(a) triple
(b) increase by a factor of 4
(c) double
(d) remain unchanged
16. Which of the following is not a neutral ligand?
(a) H2O
(b) NH3
(c) ONO
(d) CO2
17. Which among the following is a false statement?
(a) Rate of zero order reaction is independent of initial concentration of reactant.
(b) Half life of a third order reaction is inversely proportional to square of initial concentration of the reactant.
(c) Molecularity of a reaction may be zero or fraction. (d) For a first order reaction, t1/2 =0.693/K.
18. Coordination number is a characteristic of which of the following?
(a) Central atom
(b) Ligand
(c) Coordination entity
(d) Coordination compound
19. Which of the following would be diamagnetic?
(a) Cu2+
(b) Ni2+
(c) Cr3+
(d) Ti3+
20. A first order reaction is 20% complete in 10 minutes. What is the specific rate constant for the reaction?
(a) 0.0970 min-1
(b) 0.009 min-1
(c) 0.0223 min-1
d) 2.223 min-1
21. Which of the following solutions has highest osmotic pressure?
(a) 1 M NaCI
(b) 1 M MgCl2
(c) 1 M urea
(d) 1M glucose.
22. Which of the following statements is false in the following?
(a) Order of a reaction may be even zero.
(b) Molecularity of a reaction is always a whole number.
(c) Molecularity and order always have same values for a reaction.
(d) Order of a reaction depends upon the mechanism of the reaction.
23. Primary and secondary valency of Pt in [Pt(en)2C12] are
(a) 4, 4
(b) 4, 6
(c) 6, 4
(d) 2, 6
24. Which of the following is correct?
(a) Valence bond theory explains the colour of the coordination compounds.
(b) [NiCl4]2-is diamagnetic in nature.
(c) EDTA is a chelating ligand.
(d) A bidentate ligand can have four coordination sites.
25. . In which of the following elements, 5f orbitals are progressively filled?
(a) Alkaline earth metals
(b) Actinoids
(c) Lanthanoids
(d) Transition elements
26. Select the correct option, among Sc(III), Ti(IV), Mn(II) and Cu(II) ions,
(a) all are paramagnetic
(b) all are diamagnetic
(c) Sc(III), Ti(IV) are paramagnetic and Mn(II), Cu(II) are diamagnetic
(d) Sc(III), Ti(IV) are diamagnetic and Mn(II), Cu(II) are paramagnetic.
27. During decomposition of an activated complex
(a) energy is always released
(b) energy is always absorbed
(c) energy does not change
(d) All of the above
28. Dichromates are generally prepared by the fusion of chromite ore with
(a) sodium carbonate
(b) potassium carbonate
(c) Both (a) and (b)
(d) Neither (a) nor (b)
29. Strong field ligands such as CN-:
(a) usually produce high spin complexes and small crystal field splittings.
(b) usually produce low spin complexes and small crystal field splittings.
(c) usually produce low spin complexes and high crystal field splittings.
(d) usually produce high spin complexes and high crystal field splittings.
30. Methyl bromide reacts with AgF to give methyl fluoride and silver bromide. This reaction is called.
(a) Fittig reaction
(b) Swartz reaction
(c) Wurtz reaction
(d) Finkelstein reaction
CBSE Board Class 12 Chemistry Important Questions 2024: Subjective
1. Assign reason for each of the following:
(i) Manganese exhibits the highest oxidation state of +7 among the 3d series of transition elements.
(ii) Transition metals and their compounds are generally found to be good catalysts in chemical reactions.
(iii) Cr²+ is reducing in nature while with the same d-orbital configuration (d¹) Mn³+ is an oxidising agent.
(iv) Zn has lowest enthalpy of atomization.
(v) Cut is unstable in an aqueous solution.
2. An alkene with molecular formula C₂H10 on ozonolysis gives a mixture of two compounds ‘B’ and ‘C’. Compound ‘B’ gives positive Fehling test and also reacts with iodine and NaOH
solution. Compound ‘C’ does not give Fehling solution test but forms iodoform. Identify the compounds ‘A’, ‘B’ and ‘C’.
3. The rate of reaction is concerned with decrease in concentration of reactants or increase in the concentration of products per unit time. It can be expressed as instantaneous rate at a particular instant of time and average rate over a large interval of time. Mathematical representation of rate of reaction is given by rate law. Rate constant and order of a reaction can be determined from rate law or its integrated rate equation.
4. In coordination compounds, metals show two types of linkages, primary and secondary. Primary valencies are ionisable and are satisfied by negatively charged ions. Secondary valencies are non-ionisable and are satisfied by neutral or negative ions having lone pair of electrons. Primary valencies are non-directional while secondary valencies decide the shape of the complexes.
(1) If PtCl2. 2NH3 does not react with AgNO3, what will be its formula?
(ii) What is the secondary valency of [Co(en)³+?
(iii) (i) Write the formula of Iron(III) hexacyanidoferrate(II).
(ii) Write the IUPAC name of [Co(NH3)CI] Cl2.
5. What are the hydrolysis products of (i) Lactose, (ii) Maltose?
6. Give the basic structural difference between starch and cellulose.
7. An organic compound ‘A’, having the molecular formula C3H8O on treatment with Cu at 573 K, gives ‘B’. ‘B’ does not reduce Fehling’s solution but gives a yellow precipitate of the compound ‘C’ with 12/NaOH. Deduce the structures of A, B and C.
8. Give reason:
(a) Measurement of osmotic pressure method is preferred for the determination of molar masses of macromolecules such as proteins and polymers.
(b) Aquatic animals are more comfortable in cold water than in warm water.
(c) Elevation of boiling point of 1 M KCl solution is nearly double than that of 1 M sugar solution.
9. Define denaturation of protein. What is the effect of denaturation on the structure of protein?
10. Predict the stereochemistry of the product formed if an optically active alkyl halide undergoes substitution reaction by Sy2 mechanism.
11. Write the structures of the products formed when anisole is treated with HI.
12. Predict the major product formed when 2-Bromobutane undergoes a reaction with alcoholic KОН.
13. Name the instrument used for measuring the angle by which the plane polarised light is rotated.
14. Give one use of CHI.
15. Which structural unit present in a detergent makes it non-biodegradable?
16. Give the structure of the monomer of polypropene.
17. Identify which liquid will have a higher vapour pressure at 90°C if the boiling points of two liquids A and B are 140°C and 180°C, respectively.
18. Will the rate constant of the reaction depend upon T if the E (activation energy) of the reaction is zero?
19. Out of zine and tin, whose coating is better to protect iron objects ?
20. For a 5% solution of urea (Molar mass = 60 g/mol), calculate the osmotic pressure at 300 K. [R0-0821 Latm K-¹ mol-1]
21. Visha took two aqueous solutions one containing 7.5 g of urea (Molar mass 60 g/mol) and the other containing 42.75 g of substance Z in 100 g of water, respectively. It was observed that both the solutions froze at the same temperature. Calculate the molar mass of Z.
22. Calculate the mass of ascorbic acid (Molar mass 176 g mol¹) to be dissolved in 75 g of acetic acid, to lower its freezing point by 1.5°C. (K=3.9 K kg mol-¹)
23. Why is glass considered a supercooled liquid?
24. Write the dispersed phase and dispersion medium of Fog.
25. Why is it necessary to avoid even traces of moisture during the use of Grignard’s Reagent?
26. When coordination compound PdC/2.3NH3 is mixed with AgNO3 solution, I mole of AgC/ is precipitated per mole of the compound. Write the structural formula of the complex.
27. Why a mixture of Carbon disulphide and acetone shows positive deviation from Raoult’s law? What type of azeotrope is formed by this mixture?
28. A current of 1.50 A was passed through an clectrolytic cell containing AgNO, solution with inert electrodes. The weight of silver deposited was 1.50 g. How long did the current flow? (Molar mass of Ag = 108 g mol, IF=96500 C mol),
29. The conductivity of a 0.01 M solution of acetic acid at 298 K is 1.65 x 104 Scr Calculate molar conductivity () of the solution.
30. An aromatic organic compound “A with molecular formula C₂H₂O gives positive DNP and iodoform tests. It neither reduces Tollens” reagent nor does it decolourise bromine water, Write the structure of “A”.
