Class-XII
(HSC)
Chemistry-1st
Paper (Theatrical)
Time: 2:30
hrs. Full
Marks : 75
[N.B: Figures
on right side indicate full marks]
Group-A (Broad type
questions)
1. a) What is quantum number? Why four quantum
numbers are used to identify an electron completely of an atom? 1+3= 4
b) What is
degree of dissociation? If the degree of dissociation of PCl5 is ‘α’
then deduce
the
expression of Kp for the equilibrium reaction below. 1+3= 4
PCl5 (g) ↔ PCl3
(g) + Cl2 (g)
c) Explain
the 2nd law of faraday’s. Calculate the charge of an electron from
Faraday’s
Law. 1+3= 4
d) At 170C and 105kPa 600ml O2
gas is collected over water. Calculate the volume and molecular mass of that
gas at STP.[ aq.vap. pressure at 17OC is 3.25kPa] 3
Or,
a) What do you understand by chemical
equilibrium? Explain – ‘Chemical equilibrium
is
always dynamic.’ 2+2= 4
b) Describe
Bohr’s postulates of related structure of atom. 4
c) What
is dry cell? With the help of figure, describe the action of a dry cell. 1+3= 4
d) 0.5 A of electricity is passed in CuSO4
solution for 10 minutes. Calculate the amount of Cu metal deposited at the
cathode. 3
2. a) What
do you understand by absolute zero temperature? What are its significances? 1+3= 4
b) What
are inert gases? Discuss the position of inert gases in the periodic table. 1+3= 4
c) Write the balanced equation of the reaction
between KI with K2Cr2O7 acidified with dil.H2SO4
with half-reaction. 4
d) 25ml NaOH
solution is first neutralized with 10ml 0.1MHCl solution. But for complete
neutralization 400ml 0.15M HCl is needed. What is the molarity of NaOH
solution? 3
Or,
a) Explain with examples the definitions of acids
and bases according to Lewis
concept. 2+2= 4
b) State
and explain Raoult’s law of lowering of vapour pressure. 2+2= 4
c) What is hybridization? Discuss sp hybrid
orbitals’ structure with example. 1+3= 4
d) A piece of iron-wire is dissolved in dilute H2SO4.
27.5ml of 0.03 M KMnO4 solution
is
needed to oxidized the solution completely. What is the mass of iron-wire? 3
3. a) What is nuclear reaction ? Write down the
difference between nuclear reaction and
chemical
reaction. 1+3= 4
b) 2A→
product; Derive an expression for rate constant of this type of 2nd
order reaction. 4
c) What is the ionic product of water? How the
scale of PH can be determined from on
product
if water? 1+3= 4
d)
Enthalpies of
formation of CH4(g), C2H4(g), CO2(g)
and H2O(g) are, -74.89, -84.52, -393.30
and
-220.20 kJmol-1 respectively. According to the given data, explain
which one will be more suitable as a fuel between CH4 and C2H6? 3
Or,
a) What do you
mean by molecularity and order of reaction? Write down the differences between
molecularity and order of reaction. 2+2= 4
b) What do you
understand by electro negativity of elements? Why Fluorine is the most
electronegative element? 1+3= 4
c) What
is reference electrode? Describe the structure of standard hydrogen
electrode.1+3= 4
d) Zn (s) ↔ Zn2+(aq) +2e-
and Cu (S) ↔ Cu2+(aq) + 2e- The standard
reduction potential
of
the electrodes are -0.76V and 0.337V
respectively . Explain whether the following
cell
reaction is possible or not: Zn (s) + Cu2+(aq) → Zn2+(aq) + Cu (s) 3
Group-B (Short type
questions)
4. a) Write
down three similarities and dissimilarities between carbon and silicon. 3
b) Explain
the size of Na+ ion is smaller than that of Na atom. 2
Or,
a) Calculate
the average kinetic energy of 1g CO2 gas at 250C. 3
b) How
will you identify Al+3? 2
5. a) Explain
the reason, which orbitals are possible among 2d, 3f and 4f. 3
b) Write
Short Notes (i) Delocalization of electrons 2
Or,
a) What
is Hund’s rule? Electronic configuration of N obeys Hund’s rule- explain. 1+2= 3
b) “Zn
is not a transition metal”-explain. 2
6. a) Give
the geometrical shape XeF2, XeF4, XeF6. 3
b) Write
two uses of radio-active isotopes. 2
Or,
a) Calculate the mean
root velocity of N2 at 270 C. 3
b) What
do you mean by STP and SATP? 2
7. a) Show
that water acts as both acid and base that is a amphoteric substance. 3
b) What
is POH? Write with example. 2
Or,
a) Explain
the different bonds present in (H2O)n. 3
b) What
is the change in a radioactive isotope after β- particle radiation? Give an
example. 2
8. a) What
is indicator? Explain the mechanism of colour-change of an indicator. 1+2= 3
b) Ice floats in water .Why? 2
Or,
a) Explain;
Corrosion is a chemical process. 3
b) Calculate
the number of C-atoms present in 2g carbon. 2
9. a) Which
one is stronger between HNO3 and H3PO4 and
why? 3
b) Explain; decimolar solution is a standard
solution. 2
Or,
a) The
PH value of Al2(SO4) solution is less than
7.Explain why. 3
b) The
pKa value of acetic acid at 250C is 4.76. How can you
prepare a buffer solution
of pH=
5? 2
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