File - cpprashanths Chemistry

SAMPLE PAPER -1
CLASS-XII
SUB - CHEMISTRY
Time Allowed: 3 Hrs
Maximum Marks: 70
General Instructions:
1. All questions are compulsory.
2. Question No. 1-8 are very short answer questions and carry 1 mark each.
3. Question No. 9-18 are short answer questions and carry 2 marks each.
4. Question No. 19-27 are also short answer questions and carry 3 marks each.
5. Question No. 28-30 are long answer questions and carry 5 marks each.
6. Use log tables if necessary, use of calculators is not allowed.
QNo.1 If rate of formation of NO is 3.6 x 10-3 mol L-1s-1 for the following reaction then calculate the rate
of disappearance of NH3.
4NH3(g) + 5O2(g)
4NO(g) + 6H2O(g)
QNo.2 What happens when a colloidal sol of Fe(OH)3 is mixed with that of As2O3?
QNo.3 SF6 is known but SH6 is not known. Why?
QNo.4 Write the IUPAC name of the following coordination compound
(i)
[Co(NH3)4(H2O)Cl]Cl2
(ii) [CrCl2(en)2]Cl (en= ethane-1,2-diamine)
QNo.5 Write the structure of (i) 2-Chloro-3-methylpentane
(ii) 4-tert-butyl-3-iodoheptane
QNo.6 How will you distinguish between 1-phenylethanol and 2-phenylethanol?
QNo.7 Write two uses of formalin.
QNo.8 Give one example each for essential and non essential amino acids.
QNo.9 An element has bcc structure with cell edge of 288 pm. The density of the element is 7.2 g/cm3.
How many atoms are present in 208 g of the element?
QNo.10 Given that the standard electrode potentials (Eo) 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 an increasing order of their reducing power.
QNo.11 For the reaction C12H22O11 + H2O
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C6H12O6 + C6H12O6, write
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(i)
Rate of reaction expression (ii) Rate law equation (iii) molecularity (iv) order
QNo.12 Draw the structure of the following:
(a) H3PO2 (b) H3PO3 (c) NO3- (d) N2O5
QNo.13 What is a semiconductor? Describe the two main types of semiconductor with example.
QNo.14 What is activation energy? How is the rate constant of a reaction related to its activation
energy?
QNo.15 Write the hybridization and shape of XeF4 and XeOF4.
o
o
o
QNo.16 Differentiate between 1 , 2 and 3 amines. Give one example of each.
QNo.17 Write the name, state of hybridization, shape and magnetic behavior of the following
complexes:
[CoCl4]2-, [Ni(CN)4]2-(At. No. Co = 27, Ni = 28)
QNo.18 How will you distinguish between (CH3)2NH and (CH3)3N?
QNo.19 A zinc rod is dipped in 0.1 M solution of ZnSO4. The salt is 95% dissociated at this dilution at 298
K. Calculate the electrode potential (EoZn2+/Zn=-0.76 V)
QNo.20 Explain what is observed:
i.
When a beam of light is passed through a colloidal solution.
ii.
An electrolyte, NaCl is added to ferric hydroxide sol.
iii.
Electric current is passed through a colloidal sol
QNo.21 Justify the placement of O, S, Se, Te and Po in the same group of the periodic table in terms of
electronic configuration, oxidation state and hybrid formation.
OR
Arrange the following in order of property indicated for each set:
i. F2, Cl2, Br2, I2 (increasing bond dissolution enthalpy)
ii. HF, HCl, HBr, HI(increasing acid strength)
iii. NH3, PH3, AsH3, SbH3, BiH3 (increasing in base strength)
QNo.22 Explain Froth floatation method. What is the role of depressant in froth floatation?
QNo.23 Arrange the following halides in the decreasing order of SN1 reactivity.
CH3CH2CH2Cl(I), CH2=CHClCH3(II) and CH3CH2CHClCH3(III)
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QNo.24 How is phenol obtained from (i) chlorobenzene (ii) aniline (iii) benzene?
QNo.25 Name the products of hydrolysis of sucrose. Why is sucrose not a reducing sugar?
QNo.26 Differentiate between addition and condensation polymers based upon mode of
polymerization. Give one example of each.
QNo.27 Describe the following with one example in each case:
(i) Tranquillizers (ii) Antihistamines (iii) Antacids
QNo.28 (a) state the following:
(i) Henry’s law about partial pressure of a gas in a mixture.
(ii) Raoults law in its general form in reference to solutions.
(b) At 298K, the vapour pressure of water is 23.75 mm Hg. Calculate the vapour pressure at the
same temperature over 5% aqueous solution of urea[(CO(NH2)2].
OR
(a) Define the terms osmosis and osmotic pressure. Is osmotic pressure of a solution a colligative
property? Explain.
(b) 10g of a substance were dissolved in water and the solution was made up to 250 cm 3. The
osmotic pressure of the solution was found to be 8 x 105 Nm-2 at 288 K. Find the molar mass
QNo.29 (a) Complete the following chemical reaction equations:
(i) MnO4-(aq) + C2O42-(aq) + H+(aq)
(ii) Cr2O7-(aq) + Fe2+(aq) H+(aq)
(b)Explain the following observation about the transition elements:
(i) There is in general an increase in the density of elements from titanium to copper
(ii) There occurs much more frequent metal-metal bonding in compounds of heavy transition
elements
(iii)The actinoid series exhibits a larger number of oxidation states than the corresponding
lanthanoid series
OR
(a) Explain the following about transition metals: (i) metallic character (ii) Oxidation states
(b) A violet compound of manganese (A) decomposes on heating to liberate oxygen and
compounds (B) and (C) of manganese are formed. Compound (C) reacts with KOH in presence of
potassium nitrate to give compound (B). On heating (C) with conc. H 2SO4 and NaCl, chlorine gas
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is liberated and a compound (D) of manganese along with other products is formed. Identify
compounds A to D and also explain the reactions involved.
QNo.30 (a) An organic compound (A) which has characteristic odour, on treatment with conc. NaOH
forms two compounds (B) and (C). (B) has molecular formula C7H8O which on oxidation gives back (A).
(C) is a sodium salt of an acid. When (C) is treated with soda lime it yields aromatic hydrocarbon (D).
Deduce the structures of (A), (B), (C) and (D). write the sequence of reactions involved.
(b) Arrange the following in increasing order of the property indicated:
(i)
(ii)
Benzoic acid, 4-Nitro benzoic acid, 3,5-dinitrobenzoic acid, 4-methoxybenzoic acid(acid
strength )
Acetaldehyde, Acetone, Di-tertbutylketone, Methyltert-butyl ketone(Reactivity towards
HCN)
OR
Complete each synthesis by filling the missing starting materials reagents or products. (X,Y and Z)
(i) C6H5CHO + CH3CH2CHO NaOH
(ii) CH3CH2CH2CH2OH
Y
(iii) CH3(CH2)9COOC2H5
Z
X
CH3CH2CH2COOH
CH3(CH2)9CHO
How will you bring about the following conversions in not more than two steps?
(i) Toulene to Benzaldehyde
(ii) Ethylcyanide to 1-phenylpropanone
SAMPLE PAPER -1
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ANSWER KEY
Time Allowed: 3 Hrs
Maximum Marks: 70
Ans.1 3.6 x 10-3 mol L-1s-1
(1)
Ans.2 Fe(OH)3 is positively charged and As2O3 is negatively charged so, charges neutralize and
coagulation occurs.
(1)
Ans.3 Flourine is strongest oxidizing agent which oxidizes sulfur to maximum oxidation state of +6,
whereas H2 is weak oxidizing agent so cannot oxidize sulfur to maximum oxidation state.
(1)
Ans.4 (i) tetraammineaquachloridocobalt (III) chloride
cobalt(III) chloride
Ans.5 CH3
CH
CH
Cl
CH3
CH2CH3
(ii) dichloride bis (ethane-1,2- diamine)
CH3CH2
(1)
CH
CH
CH2CH2CH3
CH3
C
CH3
CH3
(1)
Ans.6 By Iodoform test
(1)
Ans.7 in preservation of anatomical specimen and manufacture of polymer like Bakelite
(1)
Ans.8 Essential – valine and non essential – glycine
(1/2x2)
Ans.9 Z=2
(1/2)
M = (a3 x N0 x density)/Z
(1/2)
M= 51.8 mol-1
(1/2)
24.17 x 1023 atoms
(1/2)
Ans.10 Ag < Cu < Fe < Mg < K
(2)
Ans.11 (i) rate = -d[C12H22O11] = +d[C6H12O6](glucose) = +d[C6H12O6](fructose)
dt
dt
(ii) rate = k[C12H22O11] (iii) molecularity = 2 (iv) order = 1
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dt
(1/2x 4)
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Ans.12
H
O
O-
P
N
OH
OH
O-
O
O
N
O
O
N
O
O
(1/2x4)
Ans.13 Semi conductor is a solid with conductivity in the intermediate range from 10-5 to 104 Ohm-1m-1
(1)
(i) N type semiconductor: Ge doped with As
(ii) P type semiconductor: Si doped with B
(1/2)
(1/2)
Ans.14 The extra minimum amount of energy absorbed by the reactant molecules so that their energy
becomes equal to threshold energy is activation energy.
(1)
K = Ae-Ea/RT
(1)
Ans.15 (i) sp3d2, square linear
(iii) sp3d2, square pyramidal
Ans.16 Primary amines are those where Nitrogen is attached to only one carbon for examples
ethylamine and 2o where nitrogen got attached to two carbons for example diethylamine and similarly
for 3o(triethylamine).
(1.5+.5)
Ans.17 (i)sp3, tetrahedral, paramagnetic
(1)
(ii)dsp2, square planar, diamagnetic
(1)
Ans.18 (i) Conduct Liebermann nitrosoamine reaction test.
(1)
Nitrosodimethylamine will give Green colour with phenol and H2SO4 and blue with NaOH
(1)
Trimethylame won’t give this test.
Ans.19 Zn2+ + 2e-
Zn
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(n=2)
(1)
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[Zn2+] = .95 x .1M= 0.095M
(1)
EZn2+/Zn = -0.79021
(1)
Ans.20 (i) tyndall effect
(1)
(ii) negatively charged sol gets prepared
(1)
(iii) electrophoresis
(1)
Ans.21
(i) Electronic configuration: all elements have ns2np4 valence shell configuration (1)
(ii) Minimum oxidation state of these elements should be -2
(iii) They can form hydrides by sharing their valence electrons forming EH2 cmpounds
(1)
(1)
OR
(i) I2 < F2 < Br2 < Cl2
(ii) HF < HCl < HBr < HI
(iii) BiH3 < SbH3 < AsH3 < PH3 < NH3
(1)
(1)
(1)
Ans.22 Froth floatation is a method concentration for sulphide ore. The lighter ore gets separated by
lighter froth.
(2)
Depressant prevent one type of ore from forming froth with air bubble.
(1)
Ans.23 In SN1 Carbocations are the intermediates. Alkyl halide (II) has most stable carbocation so most
reactive.
(1.5)
Out of alkyl halides (I) and (III), (III) gives more stable 2o carbocation, so more reactive than (I).
(1.5)
Ans.24
(i) Chlorobenzene is heated with 6-8% NaOH solution at 623 K under 320 atmospheric pressure
(ii) Aniline is treated with diazonium salt and then hydrolyzed to produce phenol
(iii) Benzene is sulphonated with oleum and benzenesulphonic acid thus formed is fused with NaOH
at 623 K and then acidisation will produce phenol
(1+1+1)
Ans.25 Sucrose produces glucose and fructose as follows
C12H22O11 + H2O
C6H12O6 + C6H12O6
It is not reducing because glucose and fructose are linked by their carbonyl groups
(2)
(1)
Ans.26
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(i) Addition polymers are formed by the repeated addition of a large number of same or different
monomer possessing double or triple bonds and process is called polymerization Ex.
Polyethylene
(1+0.5)
(ii) Condensation polymers are formed by repeated condensation reaction between two
bifunctional and trifunctional monomer unitsusually accompanied by elimination of water,
alcohol etc. this process id called condensation polymerization. Ex. Nylon 6,6
(1+0.5)
Ans.27
(i) Antihistamine are drugs which suppress the action of histamine responsible for secretion of
many fluids. They prevent the binding of histamine with the receptors.
(1)
(ii) Noradrenaline is a neurotransmitter which plays an important role in mood changes. In case of
depression, the person has low level of noradrenaline. In order to remove this depression
tranquillizers are used. These drugs inhibit the enzyme that catalyzes the degradation of
noradrenaline
(1)
(iii) Usual antacids control only the symptoms and not the cause. They work by neutralizing the acid
produced in the stomach but do not control the cause of production of more HCl.
(1)
Ans.28
(i) The solubility of of a gas in a liquid at a particular is directly proportional to the pressure of the
gas in equilibrium with the liquid at that temperature
(1)
(ii) In a solution, the vapor pressure of a component at a given temperature is equal to the mole
fraction of that component in solution multiplied by vapor pressure of that component in
the pure state.
(1)
() w2 = 5g, w1 = 95g
(1)
(23.75-Ps)/Po = (5 x 18)/(60 x 95)
(1)
Ps = 23.375
(1)
OR
(a) Osmotic pressure is defined as the equilibrium hydrostatic pressure of the column setup as a
result of osmosis.
(1)
Osmotic pressure depends on number of moles of solute irrespective of the nature of the solute,
proving it to be a colligative property
(1)
(b) W2 = 10g; V= 2.5 x 10-4 m3
M2 = (w2RT)/Vπ
M2 = 119.7gmol-1
Ans.29 2MnO4-(aq) + 5C2O42-(aq) +16H+(aq)
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(1)
(1)
(1)
2Mn2+ + 8H2O + 10CO2
(1)
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Cr2O7-(aq) + 6Fe2+(aq)+14H+(aq)
2Cr3+ + 6Fe3+ + 7H2O
(1)
(i) From left to right the atomic radii decreases due to increase in nuclear charge (1)
(ii) The valence electrons are loosly held so metal to metal bond are more frequent (1)
(iii) It because of very small energy gap between 5f, 6d and 7s subshells. All electrons can take part
in bond formation
(1)
OR
(i) Except for mercury which is a liquid, all the transition elements have typical metallic structure.
They exhibit all the characterstics of metals
(1)
(ii) All transition elements have the oxidation number of (mainly)+2, increasing upto +8
(1)
(iii) A = KMnO4
B = K2MnO4
C = MnO2
D = MnCl2
(0.5 x 4 +1)
Ans.30 (a) (A) C6H5CHO
(1 for complete reaction)
(B)C6H5CH2OH
(C) C6H5COONa
(D) C6H6
(0.5x4)
(b) (i) 4-methoxybenzoic acid < Benzoic acid < 4-Nitro benzoic acid < 3,5-dinitrobenzoic acid
(ii) Di-tertbutylketone < Methyltert-butylketone < Acetaldehyde< Acetone
(1+1)
OR
(a) (i) X = C6H5CH(OH)CH(CH3)CHO
(b) (i) C6H5-CH3
Cl2/hv C6H5-CHCl2
() CH3CH2CN
PhMgBr
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(ii) Y = KMnO4 (iii) Z = DIBAL-H/H2O)
H 2O
C6H5-CHO
PhC=(NMgBr)CH2CH3
H2O
PhCOCH2CH3
(1x3)
(1+1)
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SAMPLE PAPER -1
Blue print
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