Pre board I (2023-24)

STUDENT’S NAME
DATE GRADE XII ROLL NO.
SUBJECT CHEMISTRY MARKS 70 TIME 3 HOURS

GENERAL INSTRUCTION:
Read the following instructions carefully and strictly follow them :
(i) This question paper contains 35 questions. All questions are compulsory.
(ii) This question paper is divided into five Sections A, B, C, D and E.
(iii) In Section A Questions no. 1 to 18 are multiple choice (MCQ) type questions, carrying 1 mark each.
(iv) In Section B Questions no. 19 to 25 very short answer (VSA) type questions, carrying 2 marks each.
(v) In Section C Questions no. 26 to 30 are short answer (SA) type questions, carrying 3 marks each.
(vi) In Section D Questions no. 31 and 32 are case-based questions carrying 4 marks each.
(vii) In Section E Questions no. 33 to 35 are long answer (LA) type questions carrying 5 marks each.
(viii) There is no overall choice. However, internal choices has been provided.
(ix) Use of calculators is not allowed.
(Section – A)
Questions no. 1 to 18 are Multiple Choice (MCQ) type Questions, carrying 1 mark each.
1 The van’t Hoff factor i accounts for
(a) degree of solubilisation of solute (b) the extent of dissociation of solute.
(c) the extent of dissolution of solute (d) the degree of decomposition of solution.
2 The emf of the cell:
Ni / Ni2+ (1.0 M) // Au3+ (1.0 M) / Au (E° = -0.25 V for Ni2+/Ni; E° = 1.5 V for Au3+/Au) is
(a) 1.25 V (b) -1.25 V (c) 1.75 V (d) 2.0 V

What type of reaction is this?

(a) Second order (b) Unimolecular (c) Pseudo-unimolecular (d) Third order
4 Anomalous electronic configuration in the 3d series are of
(a) Cr and Fe (b) Cu and Zn (c) Fe and Cu (d) Cr and Cu
51. The complex ions [Co(NH3)5(NO2)]2+ and [Co(NH3)5 (ONO)]2+ are called
(a) Ionization isomers (b) Linkage isomers (c) Co-ordination isomers (d) Geometrical isomers
62. Fitting reaction can be used to prepare
(a) Toluene (b) Acetophenone (c) Diphenyl (d) Chlorobenzene
7 The molal elevation constant depends upon
(a) nature of solute (b) nature of the solvent (c) vapour pressure of the solution (d) enthalpy change
8 The charge required for the reduction of 1 mol of MnO4– to MnO2 is
(a) 1 F (b) 3 F (c) 5 F (d) 6 F
9 What will be the fraction of molecules having energy equal to or greater than activation energy, Ea?
(a) K (b) A (c) Ae-Ea/Rt (d) e-Ea/Rt
10 Which of the following has the maximum number of unpaired electrons?
(a) Mg2+ (b) Ti3+ (c) V3+ (d) Fe2+
11 Mohr’s salt is
(a) Fe2(SO4) 3 . (NH4)2SO4 . 6H2O (b) FeSO4 . (NH4)2 . SO4 . 6H2O
(c) MgSO4 . 7H2O (d) FeSO4 . 7H2O
12 Identify the end product (C) in the following sequence:
1
13 Phenol reacts with Br2 in CS2 at low temperature to give
(a)o-Bromophenol
(b)o-and-p-bromophenols
(c)p-Bromophenol (d) 2, 4, 6Tribromophenol
14 Which of the following cannot reduce Fehling’s solution?
(a)Formic acid (b)Acetic acid
(c)Formaldehyde (d) Acetaldehyde
15 Oxidation of aniline with K2Cr2O7/H2SO4 gives
(a) phenylhydroxylamine (b) p-benzoquinone (c) nitrosobenzene (d) nitrobenzene
16 HVZ reaction is used to prepare
(a)ß-haloacid (b)α-haloacid (c)α,ß-unsaturated adduct (d) None of these
17 The functional group which is found in amino acids is
(a)COOH (b)NH2 (c)CH3 (d) both (a) and (b).
18 The protein responsible for blood clotting is
(a) Albumins (b) Globulins (c) Fibroin (d) Fibrinogen
(SECTION – B )
19 Explain why aquatic species are more comfortable in cold water rather than in warm water.
20 Given that the standard electrode potentials (E°) of metals are :
K+/K = -2.93 V, Ag+/Ag = 0.80 V, Cu2+/Cu = 0.34 V,
Mg2+/Mg = -2.37 V, Cr3+/Cr = -0.74 V, Fe2+/Fe = -0.44 V.
Arrange these metals in increasing order of their reducing power.
OR
What is the effect of adding a catalyst on
(a) Activation energy (Ea), and
(b) Gibbs energy (AG) of a reaction?
21 Express the rate of the following reaction in terms of the formation of ammonia :
N2(g) + 3H2(g) → 2NH3(g)
22 What is meant by chelate effect?
OR
Which of the following is more stable complex and why?
[Co(NH3)6]3+ and [Co(en)3]
23 How would you convert ethanol to ethene?
24 Draw the structural formula of 1-phenyl propan- 1-one molecule.
25 Write the structure of the product obtained when glucose is oxidised with nitric acid.

(SECTION- C)
26 Illustrate the following reactions giving a chemical equation for each :
(i) Kolbe’s reaction
(ii) Williamsons synthesis of an ether
27 Complete the following reaction equations :

28 (a) For a reaction A + B → P, the rate law is given by, r = k[A]1/2 [B]2.
What is the order of this reaction?
(b) A first order reaction is found to have a rate constant k = 5.5 × 10-14 s-1. Find the half life of the
2
 reaction.
29 18 g of glucose, C6H12O6 (Molar mass – 180 g mol-1) is dissolved in 1 kg of water in a sauce pan. At what
temperature will this solution boil? (Kb for water = 0.52 K kg mol-1, boiling point of pure water = 373.15
K)
OR
Derive expression for Raoult’s law when the solute is non-volatile.
30 [Fe(H2O)6]3+ is strongly paramagnetic whereas [Fe(CN)6]3- is weakly paramagnetic. Explain. (At. no. Fe =
26)
(SECTION – D)
31 Read the passage given below and answer the following questions:
Aldehydes and ketones are reduced to primary and secondary alcohols respectively by NaBH4 or
LiAIH4 as well as catalytic hydrogenation. The carbonyl group of aldehydes and ketones is reduced

to group on treatment with Zn-Hg and conc. HCI (Clemmensen reduction) or with hydrazine
followed by NaOH or KOH in highly boiling solvent such, as ethylene glycol (Wolff- Kishner reduction).
Aldehydes differ from ketones in their oxidation reactions. Aldehydes are easily oxidised to carboxylic
acids on treatment with HNO3, KMnO4, K2Cr2O7 etc. Even mild oxidising agents mainly Tollens' reagent
and Fehling's solution also oxidise aldehydes. Ketones are generally oxidised under vigorous conditions
i.e., strong oxidising agents and at elevated temperatures, to give mixture of carboxylic acids having lesser
number of C-atoms than the parent ketone.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Which of the following cannot be made by reduction of ketone or aldehyde with NaBH4 in methanol?
(a) 1-Butanol (b) 2-Butanol
(c) 2-Methyl-I-propanol (d) 2-Methyl-2-propanol
(ii) The carbonyl compound producing an optically active product by reaction with LiAlH 4 is
(a) propanone (b) butanone (c) 3-pentanone (d) benzophenone
(iii) A substance C4H10O(X) yields on oxidation a compound C4H8O which gives an oxime and a positive
iodoform test. The substance X on treatment with cone. H2S04 gives C4Hs. The structure of the
compound (X) is
(a) CH3CH2CH2CH2OH (b) CH3CH(OH)CH2CH3
(c) (CH3)3COH (d) CH3CH2-O-CH2CH3

(iv) In the oxidation of by acidified K2Cr2O7, the products are

32 Read the passage given below and answer the following questions:
When a protein in its native form, is subjected to physical changes like change in temperature or chemical
changes like change in pH, the hydrogen bonds are disturbed. Due to this, globules unfold and helix get
uncoiled and protein loses its biological activity. This is called denaturation of protein.
The denaturation causes change in secondary and tertiary structures but primary structures remains intact.
Examples of denaturation of protein are coagulation of egg white on boiling, curdling of milk, formation
of cheese when an acid is added to milk.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Mark the wrong statement about denaturation of proteins
(a) The primary structure of the protein does not change
(b) Globular proteins are converted into fibrous proteins.
(c) Fibrous proteins are converted into globular proteins.
3
 (d) The biological activity of the protein is destroyed.

(ii) Which structure(s) of proteins remains(s) intact during denaturation process?

(a) Both secondary and tertiary structures (b) Primary structure only
(c) Secondary structure only (d) Tertiary structure only
(iii) Cheese is a
(a) globular protein (b) conjugated protein
(c) denatured protein (d) derived protein
(iv) Secondary structure of protein refers to
(a) mainly denatured proteins and structure of prosthetic groups
(b) three-dimensional structure, especially the bond between amino acid residues that are distant from each other
(c) linear sequence of amino acid residues in the polypeptide chain
(d) regular folding patterns of continuous portions of the polypeptide chain
(SECTION – E)
33 (a) Define the following terms :
(i) Limiting molar conductivity (ii) Fuel cell
(b) Resistance of a conductivity cell filled with 0.1 mol L-1 KCl solution is 100 Ω. If the resistance of the
same cell when filled with 0.02 mol L-1 KCl solution is 520 Ω, calculate the conductivity and molar
conductivity of 0.02 mol L-1 KCl solution. The conductivity of 0.1 mol L-1 KCl solution is 1.29 × 10-2 Ω-
1
cm-1
34 (a) How would you account for the following :
(i) Many of the transition elements and their compounds can act as good catalysts.
(ii) The metallic radii of the third (5d) series of transition elements are virtually the same as those of
the corresponding members of the second series.
(iii) There is a greater range of oxidation states among the actinoids than among the lanthanoids.
(b) Complete the following chemical equations :
(i) MnO4 (aq) + S2O32- (aq) + H2O (1) →
(ii) Cr2O72- (aq) + Fe2+ (aq) + H+ (aq) →
OR
(a) (i) What is lanthanoid contraction? Mention its main consequences.
(ii) Write the balanced ionic equation for the reaction between ferrous sulphate and acidified
potassium permanganate solution.
(b) Complete the following chemical equations :

35 (a) Giving an example for each describe the following reactions :

(i) Hofmann’s bromamide reaction
(ii) Gatterman reaction
(iii) A coupling reaction
(b) In the following cases rearrange the compounds as directed :
(i) In an increasing order of basic strength :
C6H5NH2, C6H5 N(CH3)2, (C2H5)2NH and CH3NH2
(ii) In a decreasing order of basic strength :
Aniline, p-nitroaniline and p-toluidine
OR
(a) State reasons for the following :
(i) pKb value for aniline is more than that for methylamine.
(ii) Ethylamine is soluble in water whereas aniline is not soluble in water.
(iii) Primary amines have higher boiling points than tertiary amines.
(b) How will you convert the following :
(i) Nitrobenzene into aniline
(ii) Ethanoic acid into methanamine