CHEMISTRY SAMPLE PAPER - II
CLASS - XII
Time : Three Hours
General Instructions
1.
All questions are compulsory.
2.
Question nos. 1 to 8 are very short answer questions and carry one mark each.
3.
Question nos. 9 to 18 are short answer questions and carry two marks each.
4.
Question nos. 19 to 27 are also short answer questions and carry three marks each.
5.
Question nos. 28 to 30 are long answer questions and carry five marks each.
6.
Use log tables if necessary. Calculators are not allowed.
Give IUPAC name of the following organic compound
1.
Max. Marks : 70
What are the physical states of dispersed phase and dispersion medium of froth?
2.
3.
Write the balanced equation for complete hydrolysis of XeF6
Write the structure of :
4 - methyl pent - 3 - en - 2 - one
4.
1
1
1
1
A compound contains two types of atoms - X and Y. It crytallises in a cubic lattice with atom X at the corners of the
unit cell and atomsY at the body centres. What is the simplest possible formula of this compound?
1
5.
6.
What is the Van’t Hoff factor for a compound which undergoes tetramerization in an organic solvent?
An ore sample of galena (PbS) is contaminated with zinc blende (ZnS). Name one chemical which can be used to
concentrate galena selectively by froth floatation method.
1
7.
1
8.
Predict the shape of CIF3 on the basis of VSEPR theory.
Ethylene glycol (molar mass = 62 g mol¯ 1) is a common automobile antifreeze. Calculate the freezing point of a
solution containing 12.4g of this substance in 100 g of water. Would it be advisable to keep this substance in the car
radiator during summer?
Given : Kf for water = 1.86K kg/mol
Kb for water = 0.512K kg/mol
2
9.
1
k
Consider the reaction A → P. The change in concentration of A with time is shown in the following plot:
10.
(18)
(i) Predict the order of the reaction.
(ii) Derive the expression for the time required for the completion of the reaction.
Free energies of formation
11.
of MgO(s) and CO(g) at 1273 K and 2273K are given below
(MgO(s)) = - 941 kJ/mol at 1273K
(MgO(s)) = - 314 kJ/mol at 2273K
(CO(g))
= - 439 kJ/mol at 1273K
(CO(g)) = - 628 kJ/mol at 2273K
On the basis of above data, predict the temperature at which carbon can be used as a reducing agent
for MgO(s).
2
Name the two components of starch. How do they differ from each other structurally?
12.
(a) What changes occur in the nature of egg proteins on boiling?
(b) Name the type of bonding which stabilizes α -helix structure in proteins.
13.
2
2
14.
Describe the mechanism of the formation of diethyl ether from ethanol in the presence of concentrated sulphuric
acid.
2
15.
Complete and name the following reactions:
2
16.
Give chemical tests to distinguish between compounds in each of the following pairs:
(i) Phenol and Benzyl alcohol
(ii) Butane-2 -ol and 2 Methyl propan - 2- ol
Predict, giving reasons, the order of basicity of the following compounds in (i) gaseous phase and (ii) in aqueous
17.
solutions
OR
Account for the following:
(a) Aniline does not undergo Friedel Crafts alkylation
(b) Although - NH2 group is an ortho and para-directing group, nitration of aniline gives alongwith ortho & para-
derivatives meta-derivative also.
Give reasons for the following :
(a) At higher altitudes, people suffer from a disease called anoxia. In this disease, they become weak and cannot
think clearly.
(b) When mercuric iodide is added to an aqueous solution of KI, the freezing point is raised.
2
18.
2
2
An element X with an atomic mass of 60g/mol has density of 6.23g cm-3. If the edge length of its cubic unit cell is
400 pm, identify the type of cubic unit cell. Calculate the radius of an atom of this element.
3
19.
(19)
20.
Write names of monomer/s of the following polymers and classify them as addition or condensation polymers.
(a) Teflon
(b) Bakelite
(c) Natural Rubber
3
(a) Give the IUPAC name of :
[Cr Cl2 (H2O)4] Cl
(b) Give the number of unpaired electrons in the following complex ions:
21.
(c) Name the isomerism exhibited by the following pair of coordination compounds:
Give one chemical test to distinguish between these two compounds.
22.
Explain the following observations:
(a) Ferric hydroxide sol gets coagulated on addition of sodium chloride solution
(b) Cottrell’s smoke precipitator is fitted at the mouth of the chimney used in factories.
(c) Physical adsorption is multilayered, while chemisorption is monolayered.
Account for the following:
(a) Chlorine water has both oxidizing and bleaching properties.
(b) H3PO2 and H3PO3 act as as good reducing agents while H3PO4 does not.
(c) On addition of ozone gas to KI solution, violet vapours are obtained.
23.
The decomposition of N2O5(g) is a first order reaction with a rate constant of 5 x 10-4 sec-1 at 45o C. i.e. 2N2O5 (g)
4NO2 (g) + O2 (g). If initial concentration of N2O5 is 0.25M, calculate its concentration after 2 min. Also
calculate half life for decomposition of N2O5 (g).
24.
(b) For an elementary reaction
the rate of appearance of C at time ‘t’ is 1.3 x 10-4 mol l-1 s-1.
Calculate at this time
(i) rate of the reaction.
(ii) Rate of disappearance of A.
(a) Which of the following two compounds would react faster by SN2 path way : 1 - bromobutane or
2 - bromobutane and why.?
(b) Allyl chloride is more reactive than n - propyl chloride towards nucleophilic substitution reaction. Explain why?
(c) Haloalkanes react with KCN to give alkyl cyanide as main product while with AgCN they form isocyanide as
main product. Give reason.
25.
Give reasons for the following:
(a) CN¯ ion is known but CP¯ ion is not known.
(b) NO2 demerises to form N2O4
(c) ICl is more reactive than I2
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