KENDRIYA VIDYALAYA SANGATHAN, RAIPUR REGION
Ist PRE-BOARD EXAMINATION - 2020-21
CLASS - XII M.M.70 SUB.– CHEMISTRY TIME: 3 HRS
General Instructions:
· There are 33 questions in this question paper. All questions are compulsory.
· Section A: Q No. 1 to 16 are objective type questions. Q.No. 1 & 2 are passage based questions carrying 4 marks each while Q.No 3 to 16 carry 1 mark each.
· Section B: Q. No. 17 to 25 are short answer questions and carry 2 marks each.
· Section C: Q. No. 26 to 30 are short answer questions and carry 3 marks each.
· Section D: Q.No. 31 to 33 are long answer questions and carry 5 marks each.
· There is no overall choice. However, internal choices have been provided
 |
SECTION A (OBJECTIVE TYPE)
1.
Read the passage
given below and answer the following questions:
Alcohols, phenols and ethers are widely used in our day
to day life. Alcohols are classified as mono, di, tri or polyhydric alcohols.
Monohydric alcohols are further classified as primary, secondary, tertiary,
allylic, vinylic and benzylic alcohols. Alcohols can be prepared by various
methods e.g. acid catalyzed hydration of alkenes, reduction of carbonyl
compounds, reduction of carboxylic acids, and reaction of Grignard’s reagent
with carbonyl compounds. On comparing acidity of phenols and alcohols we find
that phenol is more acidic because it gives H+ ion more
easily and phenoxide ion gets stability due to resonance. Alcohols can be
transformed into carbonyl compounds by oxidation and dehydrogenation process.
Phenols and aromatic ethers are o- & p- directing towards electrophilic
substitution reactions.
The following questions are multiple choice questions. Choose the appropriate option.(i) With dilute HNO3 at low temperature (298K), phenol gives:
(a) O-nitrophenol
(b) 0- & p- nitro phenol
(c) m- nitro phenol
(d) picric acid
(ii) Ethanol on dehydrogenation using Cu based catalyst gives a carbonyl compound “X”. The compound “X” can also be obtained by the ozonolysis of :
(a) But-1-ene
(b) Ethene
(c) But-2-ene
(d) Propene
OR
Correct increasing order of acidic strength is:
(a) Ethanol<Phenol<p- Cresol
(b) Phenol<Ethanol<p- Cresol
(c) p- Cresol<Phenol<p- nitro phenol
(d) p- nitro phenol<Phenol<p- cresol
(iii) Reaction of propanone with CH3-Mg-Br followed by hydrolysis gives:
(a) Butan-2-ol
(b) 2-Methylpropanol
(c) Propan-2-ol
(d) 2-Methyl-2-propanol
(iv) An alcohol (in excess) when heated with conc. H2SO4 at 413K gives an ether X, which on reacting with excess of HI gives only Ethyl iodide. The alcohol and ether would be:
(a) Ethanol & Ethoxy ethane
(b) Propanol & Ethoxy ethane
(c)Propanol & Methoxyethane
(d) Ethanol & Methoxy ethane
2. Read the passage given below
and answer the following questions (Assertion-reason based):
Adsorption is a surface phenomenon
and are of two types- Physical & chemical adsorption. On the basis of Cause
of adsorption, specificity, enthalpy of adsorption, temperature dependence etc,
physical and chemical adsorptions can be differentiated. Rate of adsorption of
a gas on solid adsorbent can be studied by plotting an isotherm called
Freundlich”s adsorption isotherm. Colloids are the heterogeneous system in
which one substance is dispersed in another substance. Colloids can be
classified on the basis of nature of interaction between dispersed phase and
dispersion medium, based on physical states of dispersed phase and dispersion
medium etc. There are so many properties of colloids have importance like-
peptization, coagulation, Tyndal effect, Brownian movement, electrophoresis
etc.
In these questions, a statement of assertion followed by a statement
of reason is given.
Choose the correct answer out of the following choices GIVEN.
(A) – Assertion & reason both statements are correct and reason is the correct explanation of assertion.
(B) – Assertion & reason both are the correct statements but reason is not the correct explanation of the assertion.
(C) – Assertion is correct statement and assertion is incorrect statement.
(D) – Assertion is incorrect statement and reason is correct statement
(v) Assertion - Enthalpy of chemisorption is high.
Reason – Chemisorption is caused by chemical bond formation.
(a) A (b) B (c) C (d) D
(vi) Assertion – Gas mask is usually used for breathing in coal mines to adsorb poisonous gases.
Reason - Physisorption decreases with increase of temperature.
(a) A (b) B (c) C (d) D
(vii) Assertion – Desorption is the process of removal of products from the catalyst’s surface
Reason – Desorption is not essential for further adsorption.
(a) A (b) B (c) C (d)
(viii) Assertion - The process of settling of colloidal particles is called peptization.
Reason – Coagulation power of an ion is directly proportional to its valency.
(a) A (b) B (c) C (d) D
OR
Assertion – Preferential adsorption is not required to get charge on colloidal particles. Reason – Potential difference between fixed layer and the diffused layer of opposite charges is called Zeta potential.
(a) A (b) B (c) C (d) D
*** Following questions (No 3 to
11) are multiple choice questions carrying 1 mark each.
3. Limiting molar conductivities of NaOH and KOH are 249.2 and 272.6 S cm2 mol-1 respectively. The difference of limiting molar conductivities of K+ & Na+ ion is-
(a) 23.4 S cm2 mol-1 (b) 14.4 S cm2 mol-1
(c) 33.4 S cm2 mol-1 (d) 46.4 S cm2 mol-1
4. Which of the following is an example of denaturation of protein?
(a) Boiling egg (b) Curding milk
(c) Both of these (d) None of these
OR
The bond between two units of monosaccharide through O atom is called
(a) Peptide linkage
(b) Pyranose ring
(c) Glycosidic linkage
(d) Furanose ring
(a) Ideal solution (b) non ideal solution
(c) Dilute solution (d) Concentrate solution
6. Zn is not considered as a transition element, because of –
(a) Inert pair effect (b) Filled 4s sub shell
(c) filled 3d sub shell (d) Common ion effect
OR
Which of the following ion has electronic configuration [Ar] 3d6?
(a) Ni2+ (b) Co2+
(c) Co3+ (d) Mn3+
7. Which of the following compound gives
ethanamine on reaction with Br2& KOH?
(a) Ethanamide (b)
Propanamide (c) Butanamide (d) Ethane nitrile
OR
IUPAC name of the product formed when
benzyl amine reacts with 2 moles CH3-Cl:
(a) N,N- dimethylaniline (b) N,N-
dimethylphenylmethanamine
(c) N-
methyl-N phenylmethanamine (d)
N,N- dimethylbenzenamine
8. Which of the following ligands is ambidentate ligand?
(a) OH- (b) NO2-
(c) NH4+ (d) H2O
OR
Oxidation number & coordination number of central metal atom in
the complex [Co(NH3)4H2OCl]Cl2 –
(a) +3 & 4 (b) +3
& 6 (c) +2 & 6 (d) +2 & 4
9. In which of the following pairs, both the ions are coloured in aqueous solutions?
(a) Ni2+& Ti3+
(b) Sc3+& Ti3+
(c) Sc3+& Co2+
(d) Ni2+& Cu+
10. C2H5-Cl on reacting with alcoholic KOH and aqueous KOH separately gives-
(a) C2H4& C2H5OH
(b) C2H2& C2H5OH
(c) C2H6& C2H5OH
(d) C2H4& C2H6
11. F – centers in an ionic crystal are –
(a) Lattice
sites containing e- (b) Interstitial sites containing e-
(c) Lattice
sites that are vacant (d)
interstitial sites that are vacant
*** Following questions (No 12 to
16) are Assertion- Reason type questions carrying 1 mark each.
(Instructions
for these questions are as same as given in question no.2)
12. Assertion – The H- bonds are formed between specific pair of
bases in DNA.
Reason – Uracil is not present in DNA.
(a) A (b) B (c) C (d) D
13. Assertion – Sulphur in vapour phase show paramagnetism.
Reason – In vapour phase S has unpaired electrons in its antibonding molecular orbitals. (a) A (b) B (c) C (d) D
14. Assertion–Henry’s constant for all the gases are same.
Reason – Mole fraction of a gas in a solution is directly proportional to the partial pressure of the gas in vapour phase.
(a) A (b) B (c) C (d) D
OR
Assertion – Ethanol and water forms maximum boiling azeotrope.
Reason – Mixture of ethanol and water shows positive deviation from Roult’s law
(a) A (b) B (c) C (d) D
15. Assertion – Carboxylic acids are more acidic than phenol.
Reason – Carboxylate ion is more stable due to delocalization of negative charge on both the oxygen atoms.
(a) A (b) B (c) C (d) D
16. Assertion – Anisole (Methoxy benzene) gives Iodobenzene and CH3-OH on reacting with HI.
Reason–Anisole gives o- & p- substituted product on electrophilic substitution reactions. (a) A (b) B (c) C (d) D
SECTION B (SHORT ANSWER - I TYPE)
*** Q.No 17 to 25 are short answer I type carrying 2 marks each.
17. Although chlorine is an electron withdrawing group, yet it is o- & p- directing in electrophilic substitution reactions. Why?
OR
Carry out the following conversions (not more than two steps)
(i) Propene to propan-1-ol
(ii) Benzene to p-bromonitrobenzene
18. The vapour pressure of pure benzene at a temperature is 0.850 bar. Vapour pressure of a solution containing 0.5g of a non volatile solid in 39g of benzene is 0.845 bar. What is the molar mass of the non volatile solid? (Molar mass of benzene = 78g/mol)
19.(a) Using CFT, write the electronic configuration of iron ion in the following complex ion: [Fe(CN)6]4-.
(b) Write the formula of the complex – Pentaamminenitriro-N-cobalt (III).
OR
(a) [NiCl4]2- & [Ni(CO)4] both have tetrahedral geometry but different magnetic behaviour. Why?
(b) Write the IUPAC name of [Fe(NH3)2(CN)4]- ion.
20. A reaction is 2nd order with respect to a reactant. How is the rate affected, if the concentration of the reactant is – (i) doubled (ii) reduced to half?
OR
The following results have been obtained during the kinetic study of the reaction- A + 2B > C + 2D
|
EXPERIMENT |
INITIAL
CONC. OF [A] |
INITIAL
CONC. OF [B] |
INITIAL
RATE |
|
1 |
0.10 |
0.10 |
3.0 X 10-4 |
|
2 |
0.30 |
0.30 |
9.0 X 10-4 |
|
3 |
0.10 |
0.30 |
3.0 X 10-4 |
|
4 |
0.20 |
0.40 |
6.0 X 10-4 |
21. The half life for radioactive decay of 14C is 5730 years. An archaeological artifact containing wood had only 80% of the 14C found in living tree. Estimate the age of the sample.(Log 5 = 0.6990, log 4 = 0.6021)
22. When ethanol is treated with HBr, the following reaction takes place-
C2H5-OH + HBr--------------------------- > C2H5-Br+ H2O
Give a mechanism for this reaction.
23. Draw the structures of followings –
(a) XeF6 (b) XeOF4
24.The following haloalkanes are hydrolysed with aq. KOH.
(a) 2- Chlorobutane (b) 2- Chloro- 2- methylpropane
Which of the above is most likely to give
a racemic mixture? Justify your answer.
25. Atoms of element B form hcp lattice and the
atoms of element A occupy 2/3rd of the
tetrahedral
voids. What is the formula of the compound formed by the element A & B?
SECTION C (SHORT ANSWER – II TYPE)
***Q.no. 26-30 are short answer II type carrying 3 marks each.
26. Give reason-
(a) Zn has the lowest enthalpy of atomization in the series Sc (21) – Zn (30).
(b) Mn can exhibit highest number of oxidation states in 3-d series.
(c) Cr2+ is reducing and Mn3+ is oxidizing when both are having d4 configuration.
OR
(a) E° (M2+/M) values for 3-d series elements are irregular.
(b) E° for Mn3+/Mn2+ is much more positive than E° Cr3+/Cr2+ or E° Fe3+/Fe2+.
(c) A transition metal can exhibit highest oxidation state in its oxides and fluorides.
27. Arrange the following in increasing order of property specified.
(a) C2H5-NH2, (C2H5)2NH, (C2H5)3N, NH3- basic strength in gaseous phase.
(b) C2H5-OH, C2H5-NH2, CH3-COOH – boiling point
(c) C6H5-NH2, C2H5-NH2 and C2H5-NH-C2H5 – pKb
OR
(a) Give a chemical test to distinguish between methanamine and N-methyl methanamine.
(b) Write a chemical equation of aniline reacts with NaNO2 and HCl followed by warming with water.
(c) Aniline gives m- nitro aniline in appreciable amount along with o- & p- nitro aniline on nitration. Why?
28. A metal crystallizes into cubic system FCC and BCC having edge lengths 3.5A°& 3.0A° respectively. Calculate the ratio of densities of FCC & BCC unit cells.
29. (a) Represent Zwitter ionic form of the simplest amino acid (Glycine).
(b) Write chemical equations of the reactions of Glucose with –
(i) HI
(ii) Bromine water
30. (a) Arrange F2, Cl2, Br2& I2 in increasing order of bond dissociation enthalpy.
(b) N & Bi do not form pentahalides. Why?
(c) Oxygen has less negative electron gain enthalpy than S. why?
SECTION D (LONG ANSWER TYPE)
***Q.no. 30-33 are long answer type carrying 5 marks each.
31. (a) Answer the following questions.
(i) What happens, when Cu reacts with hot &conc, HNO3?
(ii) Interhalogen compounds are more reactive than pure halogens. Why? (b)Element X has lowest boiling point (4.2K). It is used as a diluent for O2 in modern diving apparatus. Identify X. Which property of this element makes it usable as diluent? Why the boiling point of gas X is so low?
OR
(a) Answer the following questions.
(i) Arrange the oxoacids of chlorine in decreasing order of acidic strength.
(ii) What happens, when chlorine gas is passed through hot & conc. NaOH?
(b) A greenish yellow gas “A” with pungent & suffocating odour is a powerful bleaching agent. “A’ on treatment with dry slaked lime gives bleaching powder. Identify “A” and explain the reason for its bleaching action. State its bleaching action is permanent or temporary.
32. (a) An organic compound “A” (C4H8O2) is hydrolysed with dilute H2SO4 to
give a carboxylic acid “B” and an alcohol “C”. Oxidation of “C” with chromic acid
gives back “B”. “C” on dehydrogenation gives ethane (C2H4). Write the chemical
equations of the reactions involved.
(b) Give a chemical test to distinguish between
following pair of compounds:
(i) Propanal and Propanone
(ii) Phenol and Benzoic acid
OR
(a) Write chemical equations involved for the following reaction-
(i)Aldol condensation
(ii) Rosenmund’s reduction
(b) How will you convert?
(i) Benzyl alcohol to phenyl ethanoic acid
(ii) Propanone to propene
(iii) Ethanal to isopropyl alcohol.
33. (a) Suggest a way to determine the Ʌ0m of water.
(b) Calculate emf of the cell at 298K in which the following reaction takes place
Ni(s) + 2 Ag+(0.002M)-- > Ni2+(0.160M) + 2 Ag(s)
(Given E0 cell = 1.05 V & Log 80 = 1.9031)
OR
(a) Given the E°:
K+/K = -2.93V, Ag+/Ag = 0.80V, Hg2+/Hg = 0.79V, Mg2+/Mg = -2.37V
& Cr3+/Cr = -0.74V. Arrange them in increasing order of reducing power with
justification.
(b) Plot a graph and show the variation of Ʌm with concentration for both strong & weak electrolytes.
Click here for CBSE Chemistry Theory sample-paper-12020-21
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