KENDRIYA
VIDYALAYA AFS AVADI CHENNAI- 600055
MODEL QUESTION PAPER – 2016
CHEMISTRY
Time : 3 Hrs. Max.Mark:
70
Class:XI
Instructions:
·
Answer all the questions.
·
Questions 1 to 5 are very short answer type and
carry one mark each. Answer them in one word or in one sentence.
·
Questions 6 to 10 are short answer type and carry
2 marks each. Answer them in 20 words.
·
Questions 11 to 22 are short answer type and
carry 3 marks each. Answer them in 30 words.
·
Question 23 is value based question and carry 4
marks.
·
Questions 24 to 26 are long answer type and carry
5 marks each. Answer them in 50 to 60 words.
·
All 5 mark questions, one 3 mark question and one
2 mark question have internal choice. There is no overall choice.
·
Use log book wherever needed. Use of calculator
or any other electronic item is strictly prohibited.
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1
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Express the
following in the scientific notation:
i) 0.0048 ii) 8008
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1
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2
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What do you
understand by the term auto protolysis of water?
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1
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3
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What is the basic
principle of Hydrogen economy?
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1
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4
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Calculate the
number of atoms in 13 moles of
He.
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1
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5
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Predict the
formulae of the stable binary compounds that would be formed by the
combination of the following pairs of elements i) Lithium and oxygen ii)
magnesium and nitrogen
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1
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6
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Distinguish
between a sigma and a pi bond.
OR
Although both CO₂ and H₂O are triatomic molecules the shape
of H₂O molecule is bent while that of CO₂ is linear. Explain this on the
basis of dipole moment?
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1+1
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7
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a.What is
photochemical smog?
b.What is BOD?
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8
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a)Alkali metals are good reducing agents.Why?
b)Why are Potassium and Cesium, rather
than Lithium used in photoelectric cells?
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2
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9
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Using
s, p, d, f notations, describe the orbital with the
following quantum numbers
(a) n = 2, l =
1, (b) n = 4, l = 0,
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2
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10
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a) CH₃ - CH₂ – CH – CH = CH - CH₂ - CHO
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CH3
(b) CH₃ - CH₂ - CH - CH₂ - CH - CH₃
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CH₂OH CH₂-CH₃
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2
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11
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a)State Hess’s
law of constant heat summation.
b) In
a process, 701 J of heat is absorbed by a system and 394 J of work is done by
the system. What is the change in
internal energy for the process?
c) For the reaction, 2Cl (g) à
Cl2 (g), what are the signs of ∆H and ∆S?
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3
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12
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a)What is an
electrophile? Give example.
b) Why is it necessary to use acetic
acid and not sulphuric acid for acidification of sodium extract for testing
sulphur by lead acetate test?
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3
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13
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What happens when
a)
Borax is heated strongly
b)
Boric acid is added to water
c)Aluminium is
treated with dilute NaOH.
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3
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14
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. Predict in which of the following,
entropy increases/decreases:(i) A liquid crystallizes into a
solid.(ii) Temperature of a crystalline
solid is raised from 0 K to 115 K.(iii) H2(g) à 2H(g)
OR
(a) Write
the conditions in terms of ∆H and ∆S when a reaction would always
spontaneous.
(b) For the reaction at 298 K
2A +B ® C
∆H = 400 KJ mol-1 8∆S = 0.2KJmol-1
k-1 At what temperature will the reaction become spontaneous?
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3
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15
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Given the standard electrode
potentials,K+/K = –2.93V, Ag+/Ag = 0.80V,Hg2+/Hg
= 0.79V
Mg2+/Mg = –2.37V. Cr3+/Cr
= –0.74V, Cu2+/Cu = 0.34V. Arrange these metals in their
increasing order of reducing power.
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3
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16
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a) Classify the following species into
lewis acids and bases
OH-, BF3, H+, F-
b) Calculate the PH of 0.02M
KOH
c) H2O can base, write its
corresponding conjugate base and conjugate Acid
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3
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17
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a)Draw cis and
trans isomers of the following compounds and also write their IUPAC names.
i)
CHCl=CHCl ii) CH3CH=CHCH3
b) What is metamerism? Give example.
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3
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18
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1.
Give reasons for the following:
(i) Cations are smaller than
neutral atoms.
(ii) Fluorine has lower
electron-gain enthalpy than chlorine.
(iii) Sulphur has lower
ionization enthalpy than phosphorus.
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3
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19
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a) In the estimation of sulphur by
carius method, 0.468 g of an organic sulphur compound afforded 0.668 g of
barium sulphate. Find the percentage
of sulphur in the given compound.
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20
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a) State
Markovnikov’s rule.
b)How will you
convert benzene into acetophenone
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3
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21
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.
(a)
n- pentane has high b.p than neo-pentane why ?
(b)
Write the structure of 3,4 di-methy hept-3-ene
(c)
Give an example for pyrolysis
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3
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22
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Complete the
following chemical reactions.
i)
PbS (s) + H2O2 (aq) à
ii)
MnO4-
(aq) + H2O2 (aq)
à
iii)
Fe3+ + H2O 2 (l)+OH_ à
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3
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23
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Scientists have
harnessed the principles of photosynthesis to develop a new way of production
of Hydrogen in a breakthrough that offers a possible solution to global
energy problems. The researchers claim the development could help unlock the
potential of Hydrogen as a clean, cheap and reliable power source. Hydrogen
can be burned to produce energy without producing emissions like those
produced by burning of fossil fuels. Hydrogen is produced by electrolysis of
water. Scientists have separated water into Hydrogen and Oxygen in a way
similar to plants’ usage of Sun’s energy to split H2O molecules
into H2 and O2. This research offers a promise in
making storage of green energy cheaper. Based on this information, answer the
following questions:
(i) Name the most abundant
element in the universe.
(ii) What are the values
exhibited by these scientists?
(iii) Why is H2 an
ideal fuel?
(iv) What are the disadvantages
of using H2 as a fuel?
.
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3
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24
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a)Alkane ‘A’
contains three C-C, eight C-H ϭ bonds and one C-C π bond. ‘A’ on ozonolysis gives two moles of an
aldehyde of molar mass 44 amu. Write
IUPAC name of ‘A’.
b)Write the reaction between (a)
hex-1-ene and HBr (i) as per Markownikoff’s rule (ii) as per peroxide effect
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25
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a) Boron
is unable to form BF6, why?
b) Suggest a reason as to why CO is
poisonous.
c) Conc.HNO3 can be
transported in aluminium container. Why?
d) What happens when boric acid is
heated strongly?
e) What happens when CO is heated with
ZnO?
OR
a) Boric acid is considered as weak
acid. Give reason.
b) Select the members of the group 14
that (i) form the most acidic oxide
ii) is commonly found in +2 oxidation state.
c) Diamond is covalent, yet it has high
melting point. Why?
d) White fumes appear around the bottle
of anhydrous aluminium chloride. Give reason
e) How is
synthetic gas produced commercially?
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5
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26
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How would you explain
(i) why is sodium less reactive than
potassium?
(ii) Why is Li2CO3
decomposed at a lower temperature whereas Sodium carbonate at higher
temperature
(iii)LiI is more
soluble than KI in enthanol.
iv).Lithium on being heated in air mainly forms the monoxide not
peroxide.
v).BeCO₃ is less stable than
MgCO₃.
2.Alkali metals are used in photoelectric cells.
3.LiCl is predominantly covalent while NaCl is ionic .
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SCORING KEY
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1
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i) 4.8x10-3 ii)
8.008x103
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½ + ½
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2
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.
Autoprotolysis refers to self ionisation of water
H2O(l) + H2O(l) ↔ H3O+
(aq) + OH- (aq)
Acid1 Base2 Acid2 Base1
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1
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3
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Transportation
and storage of energy in the form of liquid or gaseous Dihydrogen
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1
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4
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1 mole of He has
6.022x1023atoms, so 13 moles of He has
13x6.022x1023 = 7.83x1024
atoms.
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1
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5
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i) Li2O ii)
Mg3N2
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½ + ½
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6
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Sigma (ϭ) bond
Pi (π) bond
It is formed due to axial This bond is
formed by the
overlap
of the two orbitals
lateral overlap of two p-
The
bonding is relatively strong.
Orbitals
The bonding is weak
OR
The Dipole moment is zero in CO2 and
the
resultant Dipole moment for H2O
is ≠ 0 this indicates bent structure for H2O molecules because
bond moment of two O-H bonds do not cancel out.
Resultant µ = 0
Resultant µH=1.84D
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1+1
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7
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a.Active
oxygen atoms react with traces of hydrocarbons present in the atmosphere and produce health hazardous materials called
photochemical smog.
B.Bio oxygen demand is a measure of the oxygen
utilized by microorganisms during oxidation of organic materials
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7
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molarity = 3M
Mass of NaCl in 1 litre solution = =3x58.5 =
=175.5g
Mass of 1L solution = 1000xdensity
=1000x1.25 =
1250g
Mass of water in solution = 1250 – 175.5 =
1074.5g
Hence. Molality(m) = moles of solution / mass of
solvent in kg
= 3/1.0745 = 2.79m
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1/2
1/2
1/2
1/2
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8
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(a)alkali
metals have very low ionisation enthalpy. Hence they can lose their valence
electron readily and can bring about
reduction
b.The ionization
energies of Potassium and Cesium are much lower than that of Lithium.
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1+1
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9
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a) 2p (b) 4s
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1+1
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10
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(a)
5-methylhept-3-en-1-ol.
(b)2-ethyl-4-methylhexan-1-ol.
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1+1
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11
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a)Hess’s law of
constant heat summation states that “The enthalpy change during a chemical
reaction is independent of the manner in which the change is brought about”
b) Heat absorbed by the system, q = +
701 J
Work done by the system w = -394 J
Change in the internal energy, ∆U =
+701 – 394 = + 307 J.
c) For the given reaction, ∆H is
negative and ∆S is negative.
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1
1
1
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12
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a)A reagent that
takes away an electron pair is called an electrophile (E+) i.e.,
electron seeking and the reaction is called electrophilic.
Example: carbocations and neutral molecules having
functional groups like carbonyl group or alkyl halides.
b) This
is because if sulphuric acid is used, it will decompose sodium sulphide (Na2S)
formed during fusion. As a result, the
solution will give a negative test for the presence of sulphur in the sample.
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1½
1½
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13
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a) When
Borax is heated strongly, it loses water of crystallization and forms
colourless, transparent glass-like bead which is made up of sodium metaborate
and boric anhydride. ∆ ∆
Na2B4O7.10H2O àNa2B4O7à
2NaBO2 + B2O3
b) When Boric acid is added to water, it
accepts a hydroxyl ion and behaves as a Lewis acid.
B(OH)3 + H2O à
[B(OH)4]-
+ H+
c) When aluminium is treated with NaOH,
it forms aluminates and hydrogen gas is liberated.
2Al +
2NaOH + 2H2O à
2NaAlO2 + 3H2
(g)
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1
1
1
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14
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(a)
decreases
(b) increases (c) increases
a)∆G = ∆H - T∆S
High T, Low ∆S and High ∆H
(b) ∆G = ∆H- T∆S
Let ∆G =0
0= 400 –T (0.2)
200
0.1
T= 2000 K
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1+1+1
1
1
1
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15
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The
lower the electrode potential, the stronger is the reducing agent. Therefore,
the increasing order of the reducing power of the given metals is Ag < Hg
< Cu < Cr < Mg < K.
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3
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16
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a) Lewis Acids : BF3,
H+ Lewis bases : OH-,
F-
(b) PH= 14 – POH
PoH= log ( 2x10-2)
POH= log
2+2
PH=
14+log2-2
=12+0.3010
=12.3010
C)H2O
accepts as well as donete H+ hence it acts on both acid & base
H3O+
¬ H2O®OH-
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1
1
1
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17
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b)It arises due to different alkyl
chains on either side of the functional group in the molecule.
Example: C4H10O represents
methoxypropane (CH3OC3H7) and ethoxyethane
(C2H5OC2H5).
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1
1
1
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18
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. (i) Cations are
formed by loss of electrons, keeping protons the same. So, effective nuclear
charge increases and size decreases.
(ii) It is due to
more inter-electronic repulsions in F than in Cl.
(iii) It is due
to stability of half-filled p-orbitals in P and not in S.
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1
1
1
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19
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Percentage of sulphur in the
compound = mass of BaSO4x32x100/233xmass of
the compound.
= 0.668x32x100/233x0.468 = 19.6%
Percentage of
sulphur in the compound = 19.6%
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20
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Markovnikov’s
rule states that the negative part of the addendum gets attached to that
carbon atom which possesses lesser number of hydrogen atoms
Benzene can be converted into acetophenone by the reaction of
benzene with acetyl chloride.
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21
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a) Due to strong
Vander waals forces.
6 5 4 3 2
1
(b) H3 C- H2C-C= C-CH-2 CH3
I I
CH3CH3
(c) C2 H6® CH2= CH2 + H2
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22
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i)PbS (s) + 4H2O2 (aq) à4 H2O + PbSO4
6H+
ii) 2MnO4- (aq) + 5H2O2 (aq) à2Mn2+ (aq) + 8H2O
+ 5O2 (g)
iii)2Fe3+
+ H2O 2 (l)+2OH_ à 2Fe2+ + 2H2 O + O2
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23
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i ) Hydrogen.
(ii) They show care for the environment
and concern for global problems.
(iii) It has highest calorific value
and produces H2O as the only by-product, which harmless.
(iv) It is highly inflammable and its
storage needs extra care.
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1
1
1
1
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24
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a)But-2-ene
b)CH3CH2CH2CH2CH=CH2
+ HBr à
CH3CH2CH2CH2CH(Br)CH3
CH3CH2CH2CH2CH=CH2
+ HBr (in the presence of
peroxide)à
CH3CH2CH2CH2CH2CH2Br
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2
1
1
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25
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a) Due to
non-availability of vacant d orbital
b) Competes with
O2 for hemoglobin and is bonded to hemoglobin
so that O2 is not carried to
cells
c) Passive layer
of Al2O3 acts as a protective layer
d) Forms HBO2
and then B2O3
e) Co2
+ Zn is formed
OR
a) Not able to
release H+ ions on its own
b) i) C ii)
Pb
c) 3 dimensional
network involves strong C-C bonds, difficult to
break
d) Anhydrous AlCl3
hydrolyses partially with atmospheric moisture
to liberate HCl gas and moist HCl appear
white
e) Passing steam
over red hot coke with equation
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1
1
1
1
1
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26
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i)Sodium and
potassium both are electropositive elements.
The ionization enthalpy of potassium is lesser than that of
sodium. That is why potassium is more
reactive than sodium. So, sodium is
less reactive than potassium
ii)Lithium ion is
small in size, whereas carbonate ion is a large anion. A substance containing a small cation and
large anion are less stable.
iii)lithium
ion, due to it smaller size, has greater polarising power hence covalent so
soluble
iv)
Li+ ions is smaller in size it is stabilized more by smaller anion
oxide ion(O2-) as compare to larger anion peroxide (022-)
v)
Be2+ ion is smaller in size than Mg2+ ion.
Be2+ion
does not form stable lattice with carbonate ion which is quite larger in
size. Mg2+ ion being larger forms relatively stable lattice with
cabonate ion.
(b)alkali metals because of their low
ionisation enthalpy can lose electron easily on irradiation , hence they are
used in photoelectric cells 1
(c)
than sodium ion, hence LiCl predominatingly is covalent while NaCl is ionic. 1
(d a.Lithium ion is small in size,
whereas carbonate ion is a large anion.
A substance containing a small cation and large anion are less stable
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