This Practice Paper provides an organized approach for students taking the CBSE board exams to prepare for their examinations by analysing all pertinent information. It also specifically addresses many common obstacles students encounter during exams; for example, students often find it difficult to differentiate between several types of questions, manage their time efficiently throughout the examination period, and create clear and well-constructed responses to these questions.
The format of the Practice Paper has been developed in a manner that is conducive to student learning, as it is laid out in an easy-to-read, easy-to-follow, and easy-to-complete format. The contents of the Practice Paper are written using exactly what the CBSE Board has listed as the most up-to-date version of the CBSE syllabus for Class XII, so that it follows exactly the way the CBSE Board structures its examinations and organizes its subject curriculum.
The Practice Paper includes key areas from the CBSE curriculum that students could be asked about in the examination and includes all different kinds of questions students may be presented with.
The intent of this Practice Paper is to give students an opportunity to prepare and to help students have a good experience while taking their examinations.
Furthermore, the Practice Paper includes a complete blend of objective, short-answer, and long-answer questions so that students are able to prepare for every question type without missing any. This allows students to determine how well they understand a topic, identify areas of weakness, and continue to strengthen their understanding through practice and self-reflection.
CBSE – Class XII
Chemistry (Model Practice Question Paper)
Time: 3 Hours
Maximum Marks: 70
GENERAL INSTRUCTIONS:
Read the following instructions carefully.
1. There are 33 questions in this question paper with internal choice.All questions are compulsory.
2. Section A consists of 16 multiple-choice questions carrying 1 mark each.
3. Section B consists of 5 short answer questions carrying 2 marks each,
4. Section C consists of 7 short answer questions carrying 3 marks each.
5. Section D consists of 2 case-based questions carrying 4 marks each.
6. Section E consists of 3 long answer questions carrying 5 marks each.
7. Use of log tables and calculators is not allowed.
Section A (1 × 16 = 16 Marks)
(Attempt all questions)
Q.1 Which factor is responsible for the depression in freezing point of a solution?
A. Nature of solvent
B. Nature of solute
C. Number of solute particles
D. Temperature of solution
Q.2 What is meant by van’t Hoff factor?
A. Ratio of mass of solute to solvent
B. Ratio of observed colligative property to calculated value
C. Moles of solute dissolved
D. Degree of ionisation
Q.3 What is the unit of molar conductivity?
A. S m⁻¹
B. S m² mol⁻¹
C. Ω m²
D. Ω⁻¹ m⁻¹
Q.4 One reason why electrochemical cells stop working after some time is:
A. Increase in temperature
B. Decrease in pressure
C. Accumulation of reaction products
D. Increase in electrode size
Q.5 The rate of reaction is defined as:
A. Change in temperature per unit time
B. Change in concentration per unit time
C. Change in volume per unit time
D. Change in pressure per unit time
Q.6 The relation between rate constant and activation energy is given by:
A. Boyle’s law
B. Faraday’s law
C. Arrhenius equation
D. Hess’s law
Q.7 Transition metals are coloured due to:
A. Presence of paired electrons
B. High atomic mass
C. d–d electronic transitions
D. Metallic bonding
Q.8 Denticity of a ligand refers to:
A. Number of metal atoms bonded
B. Charge on the ligand
C. Number of donor atoms present
D. Shape of the ligand
Q.9 Zinc is not considered a transition element because:
A. It has low melting point
B. It shows variable oxidation states
C. It has completely filled d-orbitals
D. It forms coloured compounds
Q.10 The SN1 reaction is a:
A. Bimolecular reaction
B. Termolecular reaction
C. Unimolecular reaction
D. Chain reaction
Q.11 Which carbocation is more stable?
A. Methyl carbocation
B. Primary carbocation
C. Secondary carbocation
D. Tertiary carbocation
Q.12 The reagent used in Reimer–Tiemann reaction is:
A. CHCl₃ and KOH
B. HCl and ZnCl₂
C. NaOH and CO₂
D. Cl₂ and sunlight
Q.13 Which vitamin is synthesised in the human body?
A. Vitamin A
B. Vitamin B₁₂
C. Vitamin C
D. Vitamin D
Q.14 The water-soluble fraction of starch is:
A. Cellulose
B. Glycogen
C. Amylose
D. Amylopectin
Q.15 A zwitter ion is a molecule which:
A. Has only positive charge
B. Has only negative charge
C. Has both positive and negative charges
D. Has no charge
Q.16 A pseudo-first-order reaction is one which:
A. Has zero activation energy
B. Appears to be first order though actually higher order
C. Is always irreversible
D. Occurs in a single step
Section B (2 × 5= 10 Marks)
(Attempt all questions)
Q.17 (a) Explain the effect of dilution on molar conductivity of strong electrolytes.
(b) Write chemical equations to explain the following reactions:
(a) Kolbe reaction
(b) Williamson ether synthesis
(c) Reimer–Tiemann reaction
(d) Friedel–Crafts reaction
Q.18 State any two differences between the order of a reaction and its molecularity.
Q.19 (a) Give a reason why manganese exhibits the highest oxidation state among transition elements.
(b) Write the IUPAC name of an ionization isomer of a coordination compound.
Q.20 (a) Distinguish between SN1 and SN2 reactions on the basis of kinetics.
(b) Describe the reactions occurring when:
(a) Chlorobenzene is treated with chlorine in presence of catalyst
(b) Ethyl chloride reacts with silver nitrite
(c) 2-Bromopentane is treated with alcoholic potassium hydroxide
Q.21 (a) Why are aldehydes more reactive than ketones towards nucleophilic addition reactions?
(b) Explain why benzoic acid is meta-directing in electrophilic substitution reactions.
Section C (3 × 7 = 21 Marks)
(Attempt all questions)
Q.22 Calculate the depression in freezing point for an aqueous solution of sodium sulphate having molality 0.0711 m. If the freezing point is −0.320 °C, determine the van’t Hoff factor.
(Given: Kf for water = 1.86 K kg mol⁻¹)
Q.23 (a) Using the given conductivity data of dilute methanoic acid, calculate its molar conductivity and degree of ionisation.
(b) Predict the products formed during electrolysis of:
(i) Aqueous silver nitrate using silver electrodes
(ii) Dilute sulphuric acid using platinum electrodes
Q.24 (a) Explain lanthanoid contraction.
(b) Why do actinoids show a wider range of oxidation states than lanthanoids?
Q.25 (a) Explain the mechanism and stereochemical outcome of SN1 reaction.
(b) State one chemical test to distinguish between:
(a) Ethanal and Propanal
(b) Acetophenone and Benzaldehyde
(c) Propanal and Propanone
(d) Benzoic acid and Ethyl benzoate
Q.26 Give one chemical test to distinguish between:
(a) Ethanal and Propanal
(b) Acetophenone and Benzaldehyde
Q.27 Write equations for the following reactions:
(a) Wolff–Kishner reduction
(b) Hell–Volhard–Zelinsky reaction
(c) Clemmensen reduction
(d) Cannizzaro reaction
(e) Aldol condensation
Q.28 (a)Explain the complementary nature of DNA.
(b)Write reactions of glucose with suitable reagents to support its structure.
Section D (4 × 2 = 8 Marks)
(Attempt all questions)
Q.29 (a) Calculate the EMF of the electrochemical cell:
Fe | Fe²⁺ (0.001 M) || H⁺ (0.01 M) | H₂ (1 bar) | Pt at 25 °C
(Given: Standard electrode potentials)
(b) Explain why Cu⁺ ions are unstable in aqueous solution.
(c) Why do transition metals have high enthalpy of atomisation?
Q.30 (a) What are fuel cells? Explain the working of hydrogen–oxygen fuel cell with electrode reactions.
(b) State one advantage of fuel cells.
Section E (5 × 3= 15 Marks)
(Attempt all questions)
Q.31 (a) Name the components of starch and identify the soluble fraction
(b) State the glycosidic linkage in sucrose
(c) Explain protein change during boiling of egg
(d) Name a water-soluble antioxidant vitamin with source
(e) Explain primary and secondary structure of proteins
(f) Name the vitamin synthesised in human body and one deficiency disease
Q.32 (a) Describe the factors affecting nucleophilic substitution reactions.
(b) Name the components of starch and identify its water-soluble fraction.
Or
Give reasons for the following:
(a) Meta-directing nature of benzoic acid
(b) High boiling point of carboxylic acids
(c) Higher reactivity of aldehydes than ketones
(d) Absence of aldol reaction in formaldehyde
(e) Lower boiling points of aldehydes and ketones compared to alcohols
(f) Non-typical carbonyl behaviour of carboxylic acids
Q.33 (a) Explain the primary and secondary structure of proteins.
(b) State the glycosidic linkage present in sucrose.
Or
Explain how the following transformations can be achieved:
(a) Benzyl chloride to benzyl alcohol
(b) Propan-2-ol to propanone
(c) Phenol to picric acid
(d) 2-Methylpropene to 2-methylpropanol
(e) Phenol to 2,4,6-tribromophenol
JAC Board Class XII Physics: Most Important Guess Questions (Long Answer Type)