Chemistry · 2019 · Set 56/3/1

CBSE Class 12 Chemistry 2019 — Set 56/3/1

CBSE Class XII Board 2019 · Set 56/3/1

Real board examination⚠ Old pattern · pre-2020 syllabus

Sets

About the 2019 exam: The 2019 exam used CBSE's older pattern — 27 questions for 70 marks, all subjective (no MCQs). All three series (56/1/1, 56/2/1, 56/3/1) are here in full (27/27), each verified against the official CBSE paper. Topics since removed from the syllabus are badged and filterable above.

This paper has 10 questions on a topic removed in CBSE’s 2023-24 syllabus update (each marked Not in syllabus). It’s kept for historical accuracy — the exam really asked it that year — but isn’t in the current syllabus and doesn’t count toward a concept’s importance. Switch to to focus on what’s still examinable.

About this paper

The real Class-12 board examination held in 2019. Every question below is solved the concept-first way. Sample papers are labelled honestly — never shown as a past exam.

Total marks: 70
Questions: 27
Duration: 180 min
Sections: 4

The marks / questions / duration above are the official exam pattern. We currently have 27 of this paper’s questions (100% of the full paper), with 27 fully solved. Questions we couldn’t yet extract or verify are held — never shown as complete.

Sections & marks

Section	Type	Questions	Marks each	Total
ASection A	Very short answer	5	1	5
BSection B	Short answer	7	2	14
CSection C	Short answer	12	3	36
DSection D	Long answer	3	5	15
Total		27		70

The question paper

The questions we hold for this paper, laid out by section. Solutions are on the Answers tab.

Board Examination

Chemistry

CBSE Class XII Board 2019 · Set 56/3/1

Series/Set: 56/3/1Roll No. ________

Time Allowed: 3 hoursMaximum Marks: 70

General Instructions

This question paper contains 27 questions divided into 4 sections — A, B, C, D.
Section A comprises 5 questions of 1 mark each (Very short answer).
Section B comprises 7 questions of 2 marks each (Short answer).
Section C comprises 12 questions of 3 marks each (Short answer).
Section D comprises 3 questions of 5 marks each (Long answer).

Above is the official exam pattern. The questions printed below are those we currently hold for this paper.

Section A

Very short answer · 1 mark each · 5 of 5 shown

Q1.

Write the IUPAC name of the following compound:

CH_2=CH-CO-CH_3

(where

-CO-

denotes a

C=O

carbonyl group)

[1]

Q2.

Arrange the following in increasing order of their acidic character : Benzoic acid, Phenol, Cresol

[1]

Q3.

Write IUPAC name of the complex

[Co(en)_2(H_2O)(CN)]^{2+}

(OR)

Using IUPAC norms, write the formula of Ammonium tetrafluoridocobaltate(II).

[1]

Q4.

What is the difference between a glycosidic linkage and a peptide linkage ?

(OR)

What is the difference between Nucleotide and Nucleoside ?

[1]

Q5.

Why is chloroform kept in dark coloured bottles ?

[1]

Page 1 of 5

Section B

Short answer · 2 marks each · 7 of 7 shown

Q1.

What happens when AgCl is doped with CdCl₂ ? What is the name of this defect ? OR What type of defect is shown by NaCl in (a) stoichiometric defects, and (b) non-stoichiometric defects ?

⚠ This question is not in the current syllabus — The Solid State (crystal defects) (removed 2023-24)

[2]

Q2.

(a) Out of 0.1 molal aqueous solution of glucose and 0.1 molal aqueous solution of KCl, which one will have higher boiling point and why ? (b) Predict whether van't Hoff factor, (i) is less than one or greater than one in the following : (i) CH₃COOH dissolved in water (ii) CH₃COOH dissolved in benzene

[2]

Q3.

Complete and balance the following equations : (a) C + H₂SO₄ (conc.) arrow (b) XeF₂ + PF₅ arrow OR Write balanced chemical equations involved in the following reactions : (a) Fluorine gas reacts with water. (b) Phosphine gas is absorbed in copper sulphate solution.

⚠ This question is not in the current syllabus — The p-Block Elements (removed 2023-24)

[2]

Q4.

Draw structures of the following : (a) H₂S₂O₇ (b) HClO₃

⚠ This question is not in the current syllabus — The p-Block Elements (removed 2023-24)

[2]

Q5.

Write anode and cathode reactions that occur in dry cell. How does a dry cell differ from a mercury cell ?

[2]

Q6.

Account for the following : (a) Gabriel phthalimide synthesis is not preferred for preparing aromatic primary amines. (b) On reaction with benzene sulphonyl chloride, primary amine yields product soluble in alkali whereas secondary amine yields product insoluble in alkali.

[2]

Q7.

Write structures of compounds A and B in each of the following reactions: (a) Aniline, C₆H₅NH₂ xrightarrowConc.H₂SO₄ A xrightarrowheat to 453-473K B (b) Benzamide, C₆H₅CONH₂ xrightarrowBr₂/NaOH A xrightarrow(CH₃CO)₂O/pyridine B

[2]

Page 2 of 5

Section C

Short answer · 3 marks each · 12 of 12 shown

Q1.

(a) Following reaction takes place in the cell : Zn(s) + Ag₂O(s) + H₂O(l) arrow Zn²⁺(aq) + 2Ag(s) + 2OH^-(aq) Calculate Δr G° of the reaction. [Given : E°(Zn²⁺/Zn) = -0.76V, E°(Ag^+/Ag) = 0.80V, 1F = 96,500Cmol⁻¹] (b) How can you determine limiting molar conductivity, (Lambda°m) for strong electrolyte and weak electrolyte ?

[3]

Q2.

Define the following with a suitable example, of each : (a) Coagulation (b) Multimolecular colloid (c) Gel OR (a) Out of starch and ferric hydroxide sol, which one can easily be coagulated and why ? (b) What is observed when an emulsion is centrifuged ? (c) What is the role of promoters and poisons in catalysis ?

⚠ This question is not in the current syllabus — Surface Chemistry (removed 2023-24)

[3]

Q3.

(a) An element crystallises in bcc lattice with a cell edge of 3 × 10⁻⁸ cm. The density of the element is 6.89gcm⁻³. Calculate the molar mass of the element. (NA = 6.022 × 10²³mol⁻¹) (b) What type of semiconductor is obtained when (i) Ge is doped with In ? (ii) Si is doped with P ?

⚠ This question is not in the current syllabus — The Solid State (removed 2023-24)

[3]

Q4.

A solution 0.1 M of Na₂SO₄ is dissolved to the extent of 95%. What would be its osmotic pressure at 27°C ? (R = 0.0821LatmK⁻¹mol⁻¹)

[3]

Q5.

Write down the reactions taking place in blast furnace related to the metallurgy of iron in the temperature range 500 K – 800 K. What is the role of limestone in the metallurgy of iron ? OR What happens when (a) Silver is leached with NaCN in the presence of air ? (b) Copper matte is charged into silica lined converter and hot air blast is blown ? (c) NaCN is added in an ore containing PbS and ZnS during concentration by froth floatation method ?

⚠ This question is not in the current syllabus — General Principles and Processes of Isolation of Elements (removed 2023-24)

[3]

Q6.

Give reasons for the following : (a) Dioxygen is a gas but sulphur a solid. (b) NO (g) released by jet aeroplanes is slowly depleting the ozone layer. (c) Interhalogens are more reactive than pure halogens.

⚠ This question is not in the current syllabus — The p-Block Elements (removed 2023-24)

[3]

Page 3 of 5

Q7.

Write the structures of monomers used to obtain the following polymers: (a) Neoprene (b) PHBV (c) Bakelite OR (a) Arrange the following polymers in decreasing order of their intermolecular forces: Bakelite, Polythene, Buna-S, Nylon-6,6 (b) Write the monomers of the following polymer: -[O-CH₂-CH₂-O-CO-C₆H₄-CO]ₙ- (a polyester in which a benzene ring, C₆H₄, links the two -CO- carbonyl groups). (c) What is the structural difference between high density polythene (HDP) and low density polythene (LDP)?

⚠ This question is not in the current syllabus — Polymers (removed 2023-24)

[3]

Q8.

(a) Why are metal hydroxides better alternatives than sodium hydrogen carbonate in antacids ? (b) Why is aspirin used in the prevention of heart-attacks ? (c) Why antihistamines do not affect the secretion of acid in stomach ? OR Define the following terms with a suitable example of each : (a) Tranquilizers (b) Antibiotics (c) Non-ionic detergents

⚠ This question is not in the current syllabus — Chemistry in Everyday Life (removed 2023-24)

[3]

Q9.

(a) Out of chlorobenzene (C₆H₅Cl) and benzyl chloride (C₆H₅CH₂Cl), which one is more reactive towards SN2 reaction and why? (b) Out of chlorobenzene (C₆H₅Cl) and p-nitrochlorobenzene (O₂N-C₆H₄-Cl), which one is more reactive towards nucleophilic substitution reaction and why? (c) Out of 3-methylbutan-1-ol, (CH₃)₂CH-CH₂-CH₂-OH, and 3-methylbutan-2-ol, (CH₃)₂CH-CH(OH)-CH₃, which one is optically active and why?

[3]

Q10.

What happens when (a) Salicylic acid is treated with (CH₃CO)₂O/H^+ ? (b) Phenol is oxidised with Na₂Cr₂O₇/H^+ ? (c) Anisole is treated with CH₃Cl/anhydrous AlCl₃ ? Write chemical equation in support of your answer.

[3]

Q11.

(a) Give one chemical test as an evidence to show that [Co(NH₃)₅Cl]SO₄ and [Co(NH₃)₅(SO₄)]Cl are ionisation isomers. (b) [NiCl₄]²⁻ is paramagnetic while [Ni(CO)₄] is diamagnetic though both are tetrahedral. Why ? (Atomic no. of Ni = 28) (c) Write the electronic configuration of Fe(III) on the basis of crystal field theory when it forms an octahedral complex in the presence of (i) strong field ligand, and (ii) weak field ligand. (Atomic no. of Fe = 26)

[3]

Q12.

Define the following terms with a suitable example of each : (a) Anomers (b) Essential amino acids (c) Denaturation of protein

[3]

Page 4 of 5

Section D

Long answer · 5 marks each · 3 of 3 shown

Q1.

(a) Define order of reaction. How does order of a reaction differ from molecularity for a complex reaction ? (b) A first order reaction is 50% complete in 25 minutes. Calculate the time for 80% completion of the reaction. OR (a) The decomposition of a hydrocarbon has value of rate constant as 2.5 × 10⁴s⁻¹ at 27°C. At what temperature would rate constant be 7.5 × 10⁴s⁻¹ if energy of activation is 19.147 × 10³Jmol⁻¹ ? (b) Write a condition under which a bimolecular reaction is kinetically first order. Give an example of such a reaction. (Given : log 2 = 0.3010, log 3 = 0.4771, log 5 = 0.6990)

[5]

Q2.

(a) Predict the main product of the following reactions: (i) 3-oxocyclohexane-1-carbaldehyde (a cyclohexanone ring bearing a -CHO group) xrightarrow[Ag(NH₃)₂]^+ (ii) CH₃-CO-CH₂-CO-OCH₃ (methyl 3-oxobutanoate) xrightarrow[(ii)H^+](i)NaBH₄ (iii) C₆H₅CHO + CH₃CHO xrightarrowdilNaOH (b) Give a simple chemical test to distinguish between acetophenone (C₆H₅-CO-CH₃) and benzophenone (C₆H₅-CO-C₆H₅). (c) Why is alpha (α) hydrogen of carbonyl compounds acidic in nature? OR (a) Write the main product formed when propanal reacts with the following reagents: (i) 2 moles of CH₃OH in presence of dry HCl (ii) Dilute NaOH (iii) H₂N-NH₂ followed by heating with KOH in ethylene glycol (b) Arrange the following compounds in increasing order of their property as indicated: (i) F-CH₂COOH, O₂N-CH₂COOH, CH₃COOH, HCOOH — acid character (ii) Acetone, Acetaldehyde, Benzaldehyde, Acetophenone — reactivity towards addition of HCN

[5]

Q3.

(a) Account for the following : (i) Manganese shows maximum number of oxidation states in 3d series. (ii) E° value for Mn³⁺/Mn²⁺ couple is much more positive than that for Cr³⁺/Cr²⁺. (iii) Ti⁴⁺ is colourless whereas V⁴⁺ is coloured in an aqueous solution. (b) Write the chemical equations for the preparation of KMnO₄ from MnO₂. Why does purple colour of acidified permanganate solution decolourise when it oxidises Fe²⁺ to Fe³⁺ ? OR (a) Write one difference between transition elements and p-block elements with reference to variability of oxidation states. (b) Why do transition metals exhibit higher enthalpies of atomization ? (c) Name an element of lanthanoid series which is well known to shown +4 oxidation state. Is it a strong oxidising agent or reducing agent ? (d) What is lanthanoid contraction ? Write its one consequence. (e) Write the ionic equation showing the oxidation of Fe(II) salt by acidified dichromate solution.

⚠ This question is not in the current syllabus — The p-Block Elements (removed 2023-24)

[5]

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