sample question paper CLASSXII 2015 -16sample question paper 2015-16
Sunday, 4 December 2016
Saturday, 3 December 2016
Saturday, 26 November 2016
some important short question class XII
50 Short Sure Questions Chemistry
class-XII March 2015-16
Q1
|
(i) Why is Frenkel defect not found in pure
alkali metal halides.
(ii) What happens to the structure
of CsCl when it is heated to about 760 k?
(iii) Fe3O4
is ferrimagnetic at room temperature and becomes paramagnetic at 850 K.Why?
(iv) When atoms are placed at the corners of
all 12 edges, how many atoms are present per unit cell?
Ans→Because ions can not get into
interstitial sites due to their larger size.(b) CsCl structure transforms into NaCl
structure.(c) due to randomization of spins at high temp.(d) at corners 8 x
1/8 = 1 atom
|
Q2
|
Explain intrinsic and extrinsic
semiconductors with suitable examples.
Ans→ Extrinsic contains impurities(B
doped with Si) & intrinsic no impurities ( Si and Ge)
|
Q3
|
A metal crystallises into two
cubic phases FCC & BCC whose edge lengths are 3.5 & 3.0 A0
respectively. Calculate the ratio of densities of FCC & BCC.
Ans→ d(fcc) = 4 x M / NA x
(3.5)3, d(bcc) = 2 x M / NA(3)3
d(fcc) / d(bcc) = 4 x 33
/ 2 x (3.5)3 = 1.26 ans
|
Q4
|
(a)Why is elevation in boiling
point of water different in the following cases;
(i) 0.1 M NaCl solution (ii)
0.1 M sugar solution
(b)Which is more concentrated 1 M or 1 m
solution & why?
(c)Two liquids A & B boil at 1450C
1900C respectively. Which of them will have higher V.P at 800C?
Ans→(a) 0.1M NaCl due to more number of ions (b) 1Molar
because it contains solvent & solute both(c) liq A
|
Q5
|
State Henry,S law for
solubility of a gas in liquid.Explain the significance of Henry,S
constant(KH). At
the same temperature, H2 is more soluble than He in water. Which
of them will have higher value of KH& Why?
Ans→ statement, Solubility α 1 / KH, H2 has lower value of KH
|
Q6
|
Molar mass of CH3CH2CHClCOOH
= 122.5,
moles of CH3CH2CHClCOOH=
10/122.5 = 0.0816, m = 0.0816/ 0.250 kg = 0.3264
α = √ Ka/C = √ 1.4 x 10—3/ 0.3264 = 0.065, i—1 i—1 i—1
α = --------, 0.065 = --------
= -------, i = 1.065
m—1 2—1 1
∆Tf = i x Kf
x m = 1.065 x 1.86 x 0.3264 = 0.650 (ANS)
|
Q7
|
Which will have greater molar
conductivity?
(i)
Solution containing 1 mol of KCl in 200 ml or 1 mol of KCl in 500 ml.
(ii) Solution containing 1 mol of
LiCl in 500 ml or 1 mol of KCl in 500 ml.
(b) Why is it not possible to
determine Λ∞m
for weak electrolytes by extrapolation?
Ans→(a) (i) 1 mol of KCl in 500 ml .
(ii) 1 mol of KCl in 500 ml (b) graph does not intersect the conc axis.
|
Q8
|
(a) Can a solution of 1 M CuSO4
be stored in a Ni vessel? E0(Cu+2/Cu) = 0.34 V, E0
(Ni+2/Ni) = -0.25V. (b) Suggest a way to determine the Λ∞m value of water.
(c) Which reaction is feasible (i)
I2 + 2e-→ 2I-, E0 =
0.54 V. (ii) Br2 + 2e- →
2Br-, E0 = 1.08 V.
Ans→ (a) No. because Cu reduces due to its high reduction
potential.
(b) Λ∞m(H2O) → Λ∞m(HCl) + Λ∞m(NaOH) -Λ∞m(NaCl)
(c) reaction (ii) is feasible
because E0 of Br2
is more than I2.
|
Q9
|
A solution of Ni(NO3)2
is electrolyzed between Pt electrodes using a current of 5 A for 20
minutes.
What mass of Ni is deposited at
the cathode?
Ans→ Q = I x t = 5
x 20 x 60 = 6000 coulomb.
Ni+2 + 2e- =
Ni ( atomic mass of Ni = 58.7)
2 x 96500 coulomb candeposite =
58.7gm Ni
6000 coulomb candeposite = 58.7 x 6000/2 x 96500 = 1.28gm(Ans)
|
Q10
|
The reaction A + B
→ C has zero order.
What is the rate equation?
Ans→ rate =
k(A)0(B)0
|
Q11
|
Define activation energy of a
reaction.
Ans→ Extra amount of energy that is
supplied from outside so that colliding particles must produce Effective
Collisions.
|
Q12
|
Give an example of a pseudo first
order reaction.
Ans→CH3COOC2H5
+ H2O → CH3COOH
+ C2H5OH
|
Q13
|
How does the value of rate
constant vary with reactant
concentration ?
Ans→α
1/ Cn-1
|
Q14
|
Identify the order of reaction.
Ans→Zero order
|
Q15
|
Define the following terms: (i)
Zeta potential (ii) Kraft
temperature (iii) Emulsion
Ans→(i) potential
difference between the fixed layer and the diffused layer of opposite charges
is called the electrokinetic
potential or zeta potential.
(ii)The formation of
micelles takes place only above a particular temperature called Kraft temperature (Tk)
and above a particular concentration called critical micelle concentration (CMC).
(iii) These are
liquid-liquid colloidal systems, i.e., the dispersion of finely divided
droplets in another liquid. If a mixture of two immiscible or partially
miscible liquids is shaken, a coarse dispersion of one liquid in the other is
obtained which is called emulsion.
|
Q16
|
What is Hardy Schulze rule? What
modification do you suggest in this law?
Ans→ The power of
coagulation is directly proportional to the fourth power of active ion. Law
must be modified as; When equimolar proportions of two oppositely charged
sols are mixed, they mutually neutralize their charge and both get coagulated
|
Q17
|
Discuss the effect of temperature
and pressure on adsorption of gases by solids
Ans→Book
|
Q18
|
Explain what is observed
when?
(i) An electrolyte is added to ferric hydroxide
sol.
(ii) An emulsion is subjected to centrifugation.
(iii) Direct current is passed
through a colloidal solution.
Ans→(a) Coagulation (b)
de-emulsification (c) electrophoresis.
|
Q19
|
What is pyrometallurgy?
Ans→ The process of extraction of
metal by heating the metal oxide with a suitable reducing agent is called thermal
reduction or pyrometallurgy
|
Q20
|
What is the role of cryolite in
electrometallurgy of Aluminium?
Ans→ To reduce the melting point of
alumina.
|
Q21
|
Out of C and CO, Which is better
reducing agent at 673K&Why?
Ans→ When C reacts with
O2 two reactions are possible; C + O2 → CO2 (1) 2C+O2→2CO (2).
It is clear from
Ellingham diagram that at 673K, ∆G0 for
the oxidation of CO is more –ive than the
reaction 1 & 2. Therefore CO is better reducing agent.
|
Q22
|
Metals do not occur in nature as
nitrates. Why?
Ans→ Nitrates of almost
all metals are soluble in water.
|
Q23
|
How is nitric acid manufactured by
Ostwald process? Give all chemical
reactions involved in the process.
Ans→Catalytic oxidation of NH3
by atmospheric oxygen
Nitric oxide thus formed combines
with O2 to give NO2
NO2 so formed,
dissolved in water to give Nitric acid
 |
Q24
|
Give reason for the
followings:
•
Nitrogen
does not form pentahalides.
•
All
five bonds in PCl5 are not equivalent.
•
SF6can
not be hydrolysed easily.
Ans→(A) Absence of vacant d orbital
(b) Axial bond pairs suffer more
repulsion than equatorial bond pairs.
(c) Sulphur is sterically
protected.
|
Q25
|
Arrange the following as
indicated:
3
(a)
HF ,HCl , HBr , HI (
decreasing order of acidic character)
(b)
NH3, PH3, AsH3, SbH3( decreasing order of themal stability)
(c)
H2O, H2S,
H2Se, H2Te (
decreasing order of reducing property)
Ans→(a) HF
<HCl<HBr< HI (b) (b)
NH3> PH3> AsH3> SbH3(c) H2O< H2S< H2Se<
H2Te
|
Q26
|
What is lanthaniodcontraction?
What is its reason? What are its consequences?
Ans→ BooK
|
Q27
|
Account for the following;
(a) The enthalpies of atomisation
of the transition metals are very high.
(b) Transition metals generally
form coloured ions.
(c) Transition metals and many of
their compounds show paramagnetic behaviour.
Ans→(a) due to unpaired electrons
(b) due to d – d transition (c) due to unpaired electrons
|
Q28
|
Describe the preparation of K2Cr2O7
from chromite ore. What is the effect of increasing pH on a
solution of potassium dichromate?
Ans→4FeCr2O4 +
8Na2CO3(or NaOH) + 7O2 → 8Na2CrO4 +
2Fe2O3 +8CO2(or 8H2O)
2Na2CrO4 +
H2SO4 → Na2Cr2O7
+ Na2SO4 + H2O
Na2Cr2O7 +
KCl → K2Cr2O7 + 2 NaCl
On increasing the PH
dichromate ion (orange) will change into chromate ion (yellow).
K2Cr2O7 + KOH
→ K2CrO4 + H2O
|
Q29
|
What is meant by chelate effect?
Give an example.
Ans→ The complexes formed by chelating
ligands like (en) and EDTA are more stable than formed by monodentate ligands
like H2O and NH3. This enhanced stability of complexes
containing ligands is called chelate effect. Example [PtCl2(en)]
|
Q30
|
Define the following terms; (a)
Homoleptic complexes (b)
Coordination entity (c) ligands
Ans→(a)The complex in which metal ion
is bonded to only one kind of donor ligands. eg [Co(NH3)]+3
(b) The central metal ion together
with ligands directly attached to it is termed as coordination sphere. It is
written in square bracket. example
[Co(NH3)]+3
|
Q31
|
(a) Geometrical isomerism is not
possible in tetrahedral complexes. Why?
(b) Give the evidence that [Co (NH3)5Cl]SO4 and [Co(NH3)5 SO4]Cl
are ionisational isomers.
Ans→(a) All positions are cis,There is
no trans position.
(b) They give different types of
ions SO4-2 and Cl- ions respectively.
|
Q32
|
Write IUPAC names of
(a)
CH3-NH-CH(CH3)2
(b) m-BrC6H4NH2
.
Ans→(a) N-methyl propan-2-amine (b) 3-bromo benzenamine
|
Q33
|
Explain Why (a)Alkyl halides, though polar,are
immiscible with water.
(b) Grignard reagents should be
prepared under anhydrous conditions
(c) o-nitrophenol is more steam volatile
than p-nitrophenol.
(d) o-methoxyphenol is less acidic than o-nitrophenol.
Ans→(a) Alkyl halides are polar
compounds and they do not form H-bonding with water.
(b) They react with water. R-Mg-X + HOH → R-H +
Mg(OH) X
(c) o-nitro phenol is steam
volatile due to intramolecular H-
bonding and intermolecular H- bonding in p-nitro phenol.
(d) o-methoxy phenol is less acidic
because of +I effect in it.
|
Q34
|
Write the equations for the
following reactions.
(a) Riemer-Tiemann reaction
(b)
Finkelstein reaction
Ans→Reimer-Tiemann reaction; Phenol
+ CHCl3+ NaOH + Heat → Salicylaldehyde.
Phenol
+ CCl4 + NaOH + Heat → Salicylic acid.
Finkelstein reaction ; CH3CH2Br
+NaI → CH3CH2I + NaBr OR CH3CH2Cl +NaI → CH3CH2I +
NaCl
|
Q35
|
Arrange the following in
increasing order of basic strength .
(a) Pri, Sec , Ter amine.
(gas phase) .
(b)
Ans→(a) Pri<
Sec < Ter amine. (b) Sec >Pri> Ter.
|
Q36
|
Account for the following
(a) There are two –NH2
groups in semicarbazides.However, only one is involved in the formation of
semicabazones.
(b)
FCH2COOH is stronger than ClCH2COOH.
Ans→(a) methylamine gives carbylamine
test. (b) benzylamine reacts with HNO2 to form C6H5CH2N2Cl
which is unstable and form C6H5CH2OH
with water.
|
Q37
|
An organic compound A (C2H6O)
reacts with sodium to form compound B with evolution of hydrogen
and gives a yellow compound C when treated with iodine &NaOH. On
heating with conc H2SO4 at 413 K, it gives a compound
D(C4H10O) which on treatment with HI at 373K gives E. D
is also obtained when B is heated with E.Identify the compounds and write the
equations involved.
Ans→
 |
Q38
|
Name the reagents used in the
following reactions.
(a) Oxidation of a primary alcohol
to aldehyde.
(b) Bromination of phenol to 2.4.6
tribromophenol.
(c) butan-2-one to butan-2-ol.
Ans→(a) Pyridinium Chloro Chromate PCC
in CH2Cl2 (b) Br2/ H2O(c) H2/
Ni, LiAlH4, NaBH4
|
Q39
|
Account for the following (a)
Ortho-nitrophenol is more acidic than ortho-methoxyphenol/.
(b) Alcohols are weaker acid than water.
(c) Alcohols are more soluble in water than hydrocarbons
Ans→(a) Due to +I effect of OCH3
group, H+can not be released easily from ortho-methoxyphenol.
(b) Due to +I effect of alkyl
group in alcohol, H+can not be released easily from
ortho-methoxyphenol.
(c) alcohols forms H-bonding with water.
|
Q40
|
Give equations for the following reactions.
(a) Dilute HNO3 with
phenol.
(b) Bromine with CS2
with phenol.
(c) 1-phenylethanol from a
suitable alkene.
Ans→(a) O-nitrophenol and
P-nitrophenol (b) O-bromophenol and P-bromophenol
(c)
 |
Q41
|
What are reducing and non-reducing
sugars? Give one example of each.
Ans→ Sugars which can reduce the
Fehling,S solution or Tollen,S reagent are called
reducing sugars.
Examples- all monosachharides,
ribose,mannose,andgalactose.
Sugars which can not reduce the
Fehling,S solution or Tollen,S reagent are called non
reducing sugars.
Examples-maltose,lactose and
sucrose.
|
Q42
|
What happens when D-glucose is
treated with the following reagents?
(a) HI (b) Bromine water (c) conc HNO3
Ans→(a) glucose + HI→ n-hexane (b) glucose + Br2(aq)→ gluconic acid[ COOH—(CH2OH)4—CH2OH].
(c) glucose + Conc HNO3 → glucaric or sachharic acid [COOH—(CH2OH)4—COOH].
|
Q43
|
What are essential and
non-essential amino acids? Give one example of each type.
Ans→ Essential-Which can not be
synthesized in our body.Valine and Leucine
Non-essential- Which can be
synthesized in our body.Glycine and Alanine.
|
Q44
|
Name the polymer used for making
nonstick utencils.
Name→(I) Teflon, Melamine
|
Q45
|
Give one point of difference
between thermosets &thermoplasts.
Ans→BooK
|
Q46
|
--- (--CH2-CH---) n---
│
C6H5 Is the above polymer homopolymer or
copolymer? Is it an addition or condensation?
Ans→ Homo & addition.
|
Q47
|
What is the difference between
polyacrylate& polyester?
Ans→ polyacrylate—homo,addition,polymerization
across C=C bond.
Polyester—copolymer,condensation,polymerization through ester linkage.
|
Q48
|
Why do drugs designed to cure some
ailment in one organ in the body not affect the other parts? Explain
with an example.
Ans→ An important point about the
receptors is that they are not disturbed evenly around the body.
For example- heart has more β
adrenergic receptors than α adrenergic receptors .This means
that a drug designed to interact
with β adrenergic receptors will act
on heart rather than a tissue
which are rich in α adrenergic
receptors .
|
Q49
|
Define the following terms with one example(Any two)
(a) Antipyretics (b)
Antioxidants (c) Antifertility
drugs
Ans→
Antipyretics—The chemical substances used to
bring down the body temperature are called
antipyretics.Paracetamol.Phenacetin,
Analgin.
Antioxidants--The substance which when added to
the fat and fat containing foods prevents their
oxidation and thus prolongs their
life.Withoutthem,fatty foods such as potato chips can not be
stored for long time.
Examples—Butylatedhydroxyanisol(BHA), Butylatedhydroxy toluene
(BHT), Propyl gallate(PG),Tertiary butyl
hydroquinone(TBHQ),
Antifertility
drugs—The
chemicals which are used to control pregnancy are called antifertility
drugs.They are mostly hormonal
contraceptives and are available for females only.They are
gonadal steroids(Oestrgen and
Progesteron).
|
Q50
|
Account for the followings:
(a) The use of aspartame is limited
to cold foods and drinks.
(b) Synthetic detergents are called
soapless soaps.
(c) Medicines should not be taken
without consulting doctors.
Ans→(a) It decomposes on heating. It nearly 100
times as sweet as cane sugar.Chemically it is methyl
ester of dipeptide of Aspartic
acid and phenylalanine.
(b) Synthetic detergents are
sodium compounds of benzene sulphonic acids whereas soaps are
sodium compounds of higher fatty acids.Soaps
are based on oils. Synthetic detergents are based on hydrocarbons.
(c) Medicines should not be taken
without consulting doctors because their wrong choice and over
dose can cause havoc and may even
prove to be fatal.
|
50 Short Sure Questions Chemistry
class-XII March 2016-17
Q1
|
Calculate
the packing efficiency of a metal crystal for a simple cubic lattice.
Suppose
edge length of unit cell = a
Radius of
sphere = r
Sphere
are touching each-other a = 2r
No of spheres per unit cell = 1
Volume
of sphere =
4Ï€r3/3
Volume
of unit cell =
a3 = (2r)3 = 8r3
Packing
efficiency
4Ï€r3/3
= ---------- x 100
= 52.4 %
8r3
|
Q2
|
An
element with density 2.8 gm/ cm-3 forms a fcc unit cell with edge
length 4 x 10-8 cm. calculate the molar mass of element. ( NA = 6.022 x 1023
mol-1)
Ans→
 |
Q3
|
How will tou distinguish between
the following pairs?
(a) Tetrahedral and octahedral
voids
(b) crystal lattice and unit cell
Ans→ (a) Tetrahedral void→ Vacant space among four spheres
having tetrahedral arrangement is called tetrahedral void.
Octahedral
void →The void formed by two equilateral triangles (six spheres)
with apices in opposite directions is called octahedral void.
(b) A regular three
dimensional arrangement of points in space is called a crystal lattice.
The smallest repeating unit in a
space lattice in three dimensional form is called a unit cell.
|
Q4
|
State
Raoult,s law for solutions of volatile liquid components. Taking a
suitable example , explain the meaning of positive deviation from Raoult,s
law.
Ans→ This law states that at a given
temperature ,the partial vapour pressure of each component in the solution is
equal to the product of vapour pressure of pure component and its mole
fraction. Consider two liquids A and B.
positive
deviation from Raoults law→ Consider a binary solution of two components A and B.
These solutions are formed when A—B interactions are weaker than A—A and B—B
interactions. The escaping tendency of molecules increases.
For
these solutions PA>PA0XA and PB> PB0XB example
ethanol and water. Ethanol and acetone
 |
Q5
|
Explain
the following; (a) Hanry,s law about the dissolution of a gas in a
liquid.
(b)
Boiling point elevation constant for a solvent.
Answer → definition in book
|
Q6
|
What
type of deviation is shown by a mixture of ethanol and acetone? Give reason.
Ans→It shows positive deviation
It is due to the weaker
interaction between acetone and ethanol than ethanol-ethanol interaction.
|
Q7
|
(i) Write colligative property
which is used to find molecular mass of macromolecules.
(ii) In
non-ideal solution, what type of deviation shows the formation of minimum
boiling azeotropes?
Ans→ (i) Osmotic pressure
(ii) Positive deviation from
Raoult,s law
|
Q8
|
What
type of cell is a lead storage battery? Write the anode and cathode reactions
and the over all cell reactions. And the overall cell reactions occurring in
the use of a lead storage battery.
Ans→ Lead storage battery is a
secondary cell.It can be recharged by passing electric current
again & again.In these cells
reactions are reversible.
Anode→
Pb + SO4-2 → PbSO4 + 2e-
Cathode→ PbO2 +
4H+ + SO4-2 + 2e- → 2PbSO4 + 2H2O
Overall→
Pb + PbO2 +2H2SO4→
2PbSO4 + 2H2O
|
Q9
|
A solution of Ni(NO3)2
is electrolyzed between Pt electrodes using a current of 5 A for 20
minutes.
What mass of Ni is deposited at
the cathode?
Ans→ Q = I x t = 5
x 20 x 60 = 6000 coulomb.
Ni+2 + 2e- =
Ni ( atomic mass of Ni = 58.7)
2 x 96500 coulomb candeposite =
58.7gm Ni
6000 coulomb candeposite = 58.7 x 6000/2 x 96500 = 1.28gm(Ans)
|
Q10
|
State Kohlrausch law of
independent migration of ions. Why does the conductivity of a solution
decrease with dilution.
Ans→ The law states that limiting
molar conductivity of an electrolyte can be stated as the sum of individual
contributions of the anions and cations of the electrolyte.
Conductivity of solution decreases
as the number of ions per unit volume of the solution decreases.
|
Q11
|
Define activation energy of a
reaction.
Ans→ Extra amount of energy that is
supplied from outside so that colliding particles must produce Effective
Collisions.
|
Q12
|
Give an example of a pseudo first
order reaction.
Ans→CH3COOC2H5
+ H2O → CH3COOH
+ C2H5OH
|
Q13
|
How does the value of rate
constant vary with reactant
concentration ?
Ans→α
1/ Cn-1
|
Q14
|
.Write
units of rate constants for zero order and second order reactions if the
concentration is expressed in mol L- and time in second.
Ans→ Zero order reaction ----- mol L-1
S-1.
Second order reaction ---mol-1
L S-1.
|
Q15
|
Express
the rate of the following reaction in terms of disappearance of hydrogen in
the reaction,
N2
+ 3H2 → 2NH3
 |
Q16
|
.Rate
constant of a first order reaction is 60 S-1. How much time will
it take to reduce the concentration of the reactant to 1/10th of
its initial value?
 |
Q17
|
Define
adsorption with an example. Why is adsorption exothermic in nature? Write the
type of adsorption based nature of forces between adsorbate and
adsorbent.
Answer→ The accumulation of molecular species at the
surface rather than in the bulk of a solid or liquid is termed adsorption. eg
gases taken in a closed vessel containing powdered charcoal.
Due to
bond formation / heat released/ interaction between adsorbate and adsorbent.
Physical ( Van der waal
adsorption) and chemical ( Langmuir adsorption).
|
Q18
|
Explain what is observed
when?
(i) An electrolyte is added to ferric hydroxide
sol.
(ii) An emulsion is subjected to centrifugation.
(iii) Direct current is passed
through a colloidal solution.
Ans→(a) Coagulation (b)
de-emulsification (c) electrophoresis.
|
Q19
|
What is pyrometallurgy?
Ans→ The process of extraction of
metal by heating the metal oxide with a suitable reducing agent is called
thermal reduction or pyrometallurgy
|
Q20
|
What is the role of cryolite in
electrometallurgy of Aluminium?
Ans→ To reduce the melting point of
alumina.
|
Q21
|
Out of C and CO, Which is better
reducing agent at 673K&Why?
Ans→ When C reacts with
O2 two reactions are possible; C + O2 → CO2 (1) 2C+O2→2CO (2).
It is clear from
Ellingham diagram that at 673K, ∆G0 for
the oxidation of CO is more –ive than the
reaction 1 & 2. Therefore CO is better reducing agent.
|
Q22
|
Metals do not occur in nature as
nitrates. Why?
Ans→ Nitrates of almost
all metals are soluble in water.
|
Q23
|
How is nitric acid manufactured by
Ostwald process? Give all chemical
reactions involved in the process.
Ans→Catalytic oxidation of NH3
by atmospheric oxygen
Nitric oxide thus formed combines
with O2 to give NO2
NO2 so formed,
dissolved in water to give Nitric acid
 |
Q24
|
Give reason for the
followings:
•
Nitrogen
does not form pentahalides.
•
All
five bonds in PCl5 are not equivalent.
•
SF6can
not be hydrolysed easily.
Ans→(A) Absence of vacant d orbital
(b) Axial bond pairs suffer more
repulsion than equatorial bond pairs.
(c) Sulphur is sterically
protected.
|
Q25
|
Arrange the following as
indicated:
3
(a)
HF ,HCl , HBr , HI (
decreasing order of acidic character)
(b)
NH3, PH3, AsH3, SbH3( decreasing order of themal stability)
(c)
H2O, H2S,
H2Se, H2Te (
decreasing order of reducing property)
Ans→(a) HF
<HCl<HBr< HI (b) (b)
NH3> PH3> AsH3> SbH3(c) H2O< H2S< H2Se<
H2Te
|
Q26
|
What is lanthaniodcontraction?
What is its reason? What are its consequences?
Ans→ BooK
|
Q27
|
Account for the following;
(a) The enthalpies of atomisation
of the transition metals are very high.
(b) Transition metals generally
form coloured ions.
(c) Transition metals and many of
their compounds show paramagnetic behaviour.
Ans→(a) due to unpaired electrons
(b) due to d – d transition (c) due to unpaired electrons
|
Q28
|
Describe the preparation of K2Cr2O7
from chromite ore. What is the effect of increasing pH on a
solution of potassium dichromate?
Ans→4FeCr2O4 +
8Na2CO3(or NaOH) + 7O2 → 8Na2CrO4 +
2Fe2O3 +8CO2(or 8H2O)
2Na2CrO4 +
H2SO4 → Na2Cr2O7
+ Na2SO4 + H2O
Na2Cr2O7 +
KCl → K2Cr2O7 + 2 NaCl
On increasing the PH
dichromate ion (orange) will change into chromate ion (yellow).
K2Cr2O7 + KOH
→ K2CrO4 + H2O
|
Q29
|
What is meant by chelate effect?
Give an example.
Ans→ The complexes formed by chelating
ligands like (en) and EDTA are more stable than formed by monodentate ligands
like H2O and NH3. This enhanced stability of complexes
containing ligands is called chelate effect. Example [PtCl2(en)]
|
Q30
|
Define the following terms; (a)
Homoleptic complexes (b)
Coordination entity (c) ligands
Ans→(a)The complex in which metal ion
is bonded to only one kind of donor ligands. eg [Co(NH3)]+3
(b) The central metal ion together
with ligands directly attached to it is termed as coordination sphere. It is
written in square bracket. example
[Co(NH3)]+3
|
Q31
|
(a) Geometrical isomerism is not
possible in tetrahedral complexes. Why?
(b) Give the evidence that [Co (NH3)5Cl]SO4 and [Co(NH3)5 SO4]Cl
are ionisational isomers.
Ans→(a) All positions are cis,There is
no trans position.
(b) They give different types of
ions SO4-2 and Cl- ions respectively.
|
Q32
|
Write IUPAC names of
(a)
CH3-NH-CH(CH3)2
(b) m-BrC6H4NH2
.
Ans→(a) N-methyl propan-2-amine (b) 3-bromo benzenamine
|
Q33
|
Explain Why (a)Alkyl halides, though polar,are
immiscible with water.
(b) Grignard reagents should be
prepared under anhydrous conditions
(c) o-nitrophenol is more steam volatile
than p-nitrophenol.
(d) o-methoxyphenol is less acidic than
o-nitrophenol.
Ans→(a) Alkyl halides are polar
compounds and they do not form H-bonding with water.
(b) They react with water. R-Mg-X + HOH → R-H +
Mg(OH) X
(c) o-nitro phenol is steam
volatile due to intramolecular H-
bonding and intermolecular H- bonding in p-nitro phenol.
(d) o-methoxy phenol is less acidic
because of +I effect in it.
|
Q34
|
Write the equations for the
following reactions.
(a) Riemer-Tiemann reaction
(b)
Finkelstein reaction
Ans→Reimer-Tiemann reaction; Phenol
+ CHCl3+ NaOH + Heat → Salicylaldehyde.
Phenol
+ CCl4 + NaOH + Heat → Salicylic acid.
Finkelstein reaction ; CH3CH2Br
+NaI → CH3CH2I + NaBr OR CH3CH2Cl +NaI → CH3CH2I +
NaCl
|
Q35
|
Arrange the following in
increasing order of basic strength .
(a)
Pri, Sec , Ter amine.
(gas phase) .
(b)
Ans→(a) Pri<
Sec < Ter amine. (b) Sec >Pri> Ter.
|
Q36
|
Account for the following
(a) There are two –NH2
groups in semicarbazides.However, only one is involved in the formation of
semicabazones.
(b)
FCH2COOH is stronger than ClCH2COOH.
Ans→(a) methylamine gives carbylamine
test. (b) benzylamine reacts with HNO2 to form C6H5CH2N2Cl
which is unstable and form C6H5CH2OH
with water.
|
Q37
|
Complete
each synthesis by giving missing reagents or products in the following.
  
Ans→
 |
Q38
|
Name the reagents used in the
following reactions.
(a) Oxidation of a primary alcohol
to aldehyde.
(b) Bromination of phenol to 2.4.6
tribromophenol.
(c) butan-2-one to butan-2-ol.
Ans→(a) Pyridinium Chloro Chromate PCC
in CH2Cl2 (b) Br2/ H2O(c) H2/
Ni, LiAlH4, NaBH4
|
Q39
|
Account for the following (a)
Ortho-nitrophenol is more acidic than ortho-methoxyphenol/.
(b) Alcohols are weaker acid than water.
(c) Alcohols are more soluble in water than hydrocarbons
Ans→(a) Due to +I effect of OCH3
group, H+can not be released easily from ortho-methoxyphenol.
(b) Due to +I effect of alkyl
group in alcohol, H+can not be released easily from
ortho-methoxyphenol.
(c) alcohols forms H-bonding with water.
|
Q40
|
An
organic compound with molecular formula C9H10O forms
2.4 DNP derivative, reduces Tollens reagent and undergoes Cannizzaro
reaction. On vigorous oxidation , it gives 1.2 benzenedicarboxylic acid.
Identify the compound.
NCERT
Q,No 12.10 page 378
Answer→
 |
Q41
|
What are reducing and non-reducing
sugars? Give one example of each.
Ans→ Sugars which can reduce the
Fehling,S solution or Tollen,S reagent are called
reducing sugars.
Examples- all monosachharides,
ribose,mannose,andgalactose.
Sugars which can not reduce the
Fehling,S solution or Tollen,S reagent are called non
reducing sugars.
Examples-maltose,lactose and
sucrose.
|
Q42
|
What happens when D-glucose is
treated with the following reagents?
(a) HI (b) Bromine water (c) conc HNO3
Ans→(a) glucose + HI→ n-hexane (b) glucose + Br2(aq)→ gluconic acid[ COOH—(CH2OH)4—CH2OH].
(c) glucose + Conc HNO3 → glucaric or sachharic acid [COOH—(CH2OH)4—COOH].
|
Q43
|
What are essential and
non-essential amino acids? Give one example of each type.
Ans→ Essential-Which can not be
synthesized in our body.Valine and Leucine
Non-essential- Which can be
synthesized in our body.Glycine and Alanine.
|
Q44
|
Explain the term co-polymerisation
and give two examples of co-polymers and reactions for their preparation.
Answer→
 |
Q45
|
Write
the name of the monomers used for getting the following polymers.
(i) Terylene
(ii) Nylon-6,6
Answer → (i) Ethylene glycol and
terephthalic acid ( ethane 1.2 diol and benzene 1.2 dicarboxylic acid)
(ii) Hexamethylene diamine
and adipic acid
|
Q46
|
Write two uses of each of the
following polymers:
(i)
Polyproplene
(ii) PVC
(iii) Nylon-6,6
Answer→ Uses :
(i)
Polypropene → Ropes , toys ,
pipes and fibres
(ii) PVC
→
Rain coat, insulating material, and water pipes
(iii) Nylon6,6 → sheets, bristles, brushes and
textile industry
|
Q47
|
What is the difference between
polyacrylate& polyester?
Ans→ polyacrylate—homo,addition,polymerization
across C=C bond.
Polyester—copolymer,condensation,polymerization through ester linkage.
|
Q48
|
Why do drugs designed to cure some
ailment in one organ in the body not affect the other parts? Explain
with an example.
Ans→ An important point about the
receptors is that they are not disturbed evenly around the body.
For example- heart has more β
adrenergic receptors than α adrenergic receptors .This means
that a drug designed to interact
with β adrenergic receptors will act
on heart rather than a tissue
which are rich in α adrenergic
receptors .
|
Q49
|
Define the following terms with one example(Any two)
(a) Antipyretics (b)
Antioxidants (c)
Antifertility drugs
Ans→
Antipyretics—The chemical substances used to
bring down the body temperature are called
antipyretics.Paracetamol.Phenacetin,
Analgin.
Antioxidants--The substance which when added to
the fat and fat containing foods prevents their
oxidation and thus prolongs their
life.Withoutthem,fatty foods such as potato chips can not be
stored for long time.
Examples—Butylatedhydroxyanisol(BHA), Butylatedhydroxy toluene
(BHT), Propyl gallate(PG),Tertiary butyl
hydroquinone(TBHQ),
Antifertility
drugs—The
chemicals which are used to control pregnancy are called antifertility
drugs.They are mostly hormonal
contraceptives and are available for females only.They are
gonadal steroids(Oestrgen and
Progesteron).
|
Q50
|
Account for the followings:
(a) The use of aspartame is limited
to cold foods and drinks.
(b) Synthetic detergents are called
soapless soaps.
(c) Medicines should not be taken
without consulting doctors.
Ans→(a) It decomposes on heating. It nearly 100
times as sweet as cane sugar.Chemically it is methyl
ester of dipeptide of Aspartic
acid and phenylalanine.
(b) Synthetic detergents are
sodium compounds of benzene sulphonic acids whereas soaps are
sodium compounds of higher fatty
acids.Soaps are based on oils. Synthetic detergents are based on hydrocarbons.
(c) Medicines should not be taken
without consulting doctors because their wrong choice and over
dose can cause havoc and may even
prove to be fatal.
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