Chemistry (Class XII)
(I)
Read the passage given below and answer the following questions:
In
spite of the predictions of stable noble gas compounds since at least 1902,
unsuccessful attempts at their
synthesis gave rise to the widely held opinion that noble gases are not only noble but
also inert. It was not until
1962 that this dogma was
shattered when Bartlett in Canada
published the first stable noble gas compound XePtF6. This discovery
triggered a worldwide frenzy in this
area, and within a short time span
many new xenon, radon, and krypton compounds were prepared and characterized. The recent discoveries show the ability
of xenon to act as a ligand. The discovery by Seppelt’s group that more
than one xenon atom can attach itself
to a metal center which in the case of gold leads to surprisingly stable Au- Xe bonds.
The bonding in [AuXe4]2+ involves
4 Xe ligands attached by relatively strong bonds to a single Au (II) center in a square planar arrangement with a Xe-Au bond length of about 274
pm This discovery provides not only the first example of multiple xenon ligands
but also represents the first strong metal - xenon
bond.
(Source: Christe, K. O. (2001). A renaissance in noble gas chemistry. Angewandte Chemie
International Edition, 40(8), 1419-1421.)
1.
In the complex ion [AuXe4]2+, Xe acts as:
a. central atom
b. ligand
c. chelating agent
d. electrophile
2.
Hybridisation shown by Au in [AuXe4]2+ is:
a. sp3
b. sp3d
c. sp3d2
d. sp2
3. Compounds of noble gases except are known.
a. Krypton
b. Radon
c. Helium
d. Xenon
4. Xe is a ligand
a. ambidentate
b. bidantate
c. unidentate
d. hexadentate
ANSWERS: 1a, 2 b 3 c 4 c
(II)
Read the passage given below and answer the following questions:
Boiling point or freezing point of liquid solution would be affected
by the dissolved solids in the liquid
phase. A soluble solid in solution has the effect of raising its boiling point
and depressing its freezing point. The addition
of non-volatile substances to a solvent decreases the vapor pressure and the added solute particles affect the
formation of pure solvent crystals. According to many researches the decrease in freezing point directly correlated to the concentration of solutes dissolved in the
solvent. This phenomenon is expressed as freezing point depression and it is useful for several applications such
as freeze concentration of liquid food
and to find the molar mass of an
unknown solute in the solution. Freeze concentration is a high-quality
liquid food concentration method where water is removed
by forming ice crystals.
This is done by cooling the liquid food below the freezing point of the
solution. The freezing point depression is referred
as a colligative property and it is proportional to the
molar concentration of the solution (m), along with vapor pressure
lowering, boiling point elevation,
and osmotic pressure. These are physical characteristics of solutions
that depend only on the identity of
the solvent and the concentration of the solute. The characters are not depending on the solute’s identity. (Jayawardena, J. A. E. C., Vanniarachchi, M. P. G., & Wansapala, M. A. J. (2017). Freezing point depression of different Sucrose solutions and coconut water.)
1. When a non-volatile solid is added to pure water it will:
a.
boil above 100oC and freeze above 0oC
b.
boil below 100oC and freeze above 0oC
c.
boil above 100oC and freeze below 0oC
d.
boil below 100oC and freeze below 0oC
2. Colligative properties are:
a. dependent only on the concentration of the solute and independent of the solvent’s and solute’s identity.
b. dependent only on the identity
of the solute and the concentration of the solute and independent of the solvent’s
identity.
c. dependent on the identity of the
solvent and solute and thus on the concentration of the solute.
d. dependent only on the identity
of the solvent and the concentration of the solute and independent of the solute’s identity.
3. Assume three samples of juices A, B and C have glucose as the only
sugar present in them. The
concentration of sample A, B
and C are 0.1M, .5M and 0.2 M respectively.
Freezing point will be highest for the fruit juice:
a. A
b. B
c. C
d. All have same freezing point
4. Identify which of the following
is a colligative property :
a. freezing point
b. boiling point
c. osmotic pressure
d. all of the above
Ans 1 (b) 2 (d) 3 (a) 4(c)
(III) Read the passage given below and answer the following questions:
The
rate of a reaction, which may also be called its velocity or speed, can be
defined with relation to the
concentration of any of the reacting substances, or to that of any product of
the reaction. If the species chosen
is a reactant which has a concentration c at time t the rate is - dc/dt,
while the rate with reference to a product having a
concentration x at time t is dx/dt. Any concentration units may be used
for expressing the rate; thus, if
moles per liter are employed
for concentration and seconds for the time, the units for
the rate are moles
liter- 1sec-1.
For gas reactions pressure units are sometimes used in place of concentrations,
so that legitimate units for the rate would be (mm. Hg) sec-1 and atm. sec-1
The order of a reaction concerns
the dependence of the rate upon the concentrations of reacting
substances; thus, if the rate is
found experimentally to be proportional to the
α th power of the concentration of one of the reactants
A, to the β th power of the concentration of a second reactant
B, and so forth, via.,
A B
rate = k C α C β (1)
the over-all order of the reaction is simply n = α + β +--------------------- (2)
Such a reaction
is said to be of the αth order with respect
to the substance A, the β th order with respect to B and so on...
(Laidler, K. J., & Glasstone, S. (1948). Rate, order and molecularity in chemical kinetics. Journal of Chemical Education, 25(7), 383.)
In the following questions, a statement of assertion
followed by a statement of reason is given.
Choose the correct answer out of the following choices on the basis of the
above passage.
A. Assertion and reason both are correct statements and reason is correct explanation for assertion.
B. Assertion and reason both are correct statements but reason is not correct
explanation for assertion.
C. Assertion is correct statement but reason is wrong statement.
D. Assertion is wrong statement but reason is correct statement.
Reason: Rate of reaction is a measure of change in concentration of product with respect to time.
2. Assertion: For a reaction: P +2Q à Products, Rate = k [P]1/2[Q]1 so the order of reaction is 1.5
Reason: Order of reaction is the sum of stoichiometric coefficients of the reactants.
3. Assertion: The unit of k is independent of order of reaction.
Reason: The unit of k is moles L-1s-1.
4. Assertion: Reactions can occur at different speeds.
Reason: Rate of reaction is also called speed of reaction.
Ans: 1B 2C 3D 4B
(IV) Read the passage given below and answer the following questions:
We
have now prepared the new, dearomatized, bipyridine-based pincer complex 3,
catalyst 3(Here refered as Cat. 3).
Remarkably, it efficiently catalyzes the selective hydrogenation of amides to form amines and alcohols (eq 1).
The reaction proceeds under mild pressure and
neutral conditions, with no additives being required. Since the reaction
proceeds well under anhydrous conditions, hydrolytic cleavage of the amide is not involved in this process.
(Balaraman, E., Gnanaprakasam, B., Shimon, L. J., & Milstein, D. (2010). Direct hydrogenation of amides to alcohols and amines under mild conditions. Journal of the American
Chemical Society, 132(47), 16756-16758.)
In the following questions, a statement of assertion
followed by a statement of reason is given.
Choose the correct answer out of the following choices on the basis of the
above passage.
A. Assertion and reason both are correct statements and reason is correct explanation for assertion.
B.
Assertion and reason both are correct statements but reason is not correct
explanation for assertion.
C. Assertion is correct statement but reason is wrong statement.
D. Assertion is wrong statement but reason is correct statement.
1. Assertion: The use of catalyst
3 is an efficient method of preparation of primary amines
Reason: Use of catalyst 3 is a step down reaction.
2. Assertion: Use of hydride catalyst
or hydrogen brings about cleavage of C-O bond in amides.
Reason: Hydride catalyst or hydrogen cause to reduction of amides.
3. Assertion: N-methyl ethanamide
on reaction with catalyst 3 will yield ethanol and methanamine.
Reason: Use of Catalyst 3 brings about cleavage of C-N bond of amides
4.
Assertion: Aniline can be prepared from suitable amide using catalyst
3
Reason: The use of catalyst 3 is limited
to aliphatic amides only.
Ans: 1B 2B 3 A 4C
(V) Read the passage given below and answer the following questions:
N N
Nucleophilic
substitution reaction of haloalkane can be conducted according to both S 1
and S 2 mechanisms.
However, which mechanism it is based on is related to such factors as the structure of haloalkane, and properties of leaving group,
nucleophilic reagent and solvent.
Influences of halogen : No matter which mechanism the nucleophilic substitution reaction
is based on, the leaving group
always leave the central carbon atom with electron pair. This is
just the opposite of the situation that nucleophilic reagent attacks the central carbon atom with electron pair. Therefore, the weaker the alkalinity of leaving group
is , the more stable
the anion formed is and it will be more easier for the leaving group to
leave the central carbon atom; that is to say, the reactant is more easier to be substituted. The
alkalinity order of halogen ion is I− < Br− < Cl− < F− and the order of their leaving tendency
should be I− > Br−
N N
> Cl− > F− . Therefore, in four halides
with the same alkyl and different halogens,
the order of substitution reaction rate is RI>
RBr > RCl > RF . In addition,
if the leaving group is very easy to
leave, many carbocation intermediates are generated in the reaction and the
reaction is based on S 1 mechanism. If the leaving group
is not easy to leave,
the reaction is based on S 2 mechanism.
N
Influences
of solvent polarity: In S 1 reaction, the polarity of the
system increases from the reactant to
the transition state, because polar solvent has a greater stabilizing effect on
the transition state than the reactant, thereby
reduce activation energy and accelerate the reaction.
In S 2 reaction,
the polarity of the
system generally does not change from the reactant
to the
N
transition state and only charge
dispersion occurs. At this time, polar solvent
has a great stabilizing effect
on Nu than the transition state, thereby increasing activation energy and
N
slow down
the
reaction
rate.
For
example,
the
decomposition
rate
(
S 1) of tertiary
chlorobutane in 25℃ water (dielectric constant
79) is 300000 times faster
than in ethanol
N
(dielectric constant
24). The reaction
rate (S 2) of 2-bromopropane and NaOH in ethanol
containing 40% water is twice slower than in absolute ethanol. In a word, the level of solvent
N N
polarity has influence on both S 1 and S 2reactions, but with different results. Generally
N
speaking, weak polar solvent
is favorable for S 2 reaction, while strong
polar solvent is
favorable
for SN1 reaction, because only under the action of polar
solvent can halogenated hydrocarbon
dissociate into carbocation and halogen ion and solvents with a strong polarity
is favorable for solvation of carbocation, increasing its stability. Generally
speaking, the
N
substitution reaction
of tertiary haloalkane is based on S 1 mechanism in solvents
with a strong polarity (for example, ethanol
containing water).
(Ding, Y. (2013).
A Brief Discussion on Nucleophilic Substitution Reaction on Saturated Carbon Atom. In Applied Mechanics and Materials (Vol.
312, pp. 433-437).
Trans Tech Publications Ltd.)
1.
SN1 mechanism
is favoured in which of the following
solvents:
a. benzene
b. carbon tetrachloride
c. acetic acid
d. carbon disulphide
2. Nucleophilic substitution will be fastest in case of:
a. 1-Chloro-2,2-dimethyl propane
b. 1-Iodo-2,2-dimethyl propane
c. 1-Bromo-2,2-dimethyl propane
d. 1-Fluoro-2,2-dimethyl propane
3.
SN1 reaction will
be fastest in which of the following
solvents?
a. Acetone (dielectric constant
21)
b. Ethanol (dielectric constant
24)
c. Methanol (dielectric constant
32)
d. Chloroform (dielectric constant
5)
4. Polar solvents make the reaction
faster as they:
a. destabilize transition state and decrease
the activation energy
b. destabilize transition state and increase
the activation energy
c. stabilize transition state and increase
the activation energy
d. stabilize transition state and decrease
the activation energy
5.
SN1 reaction
will be fastest in case of:
a. 1-Chloro-2-methyl propane
b. 1-Iodo-2-methyl propane
c. 1-Chlorobutane
d. 1-Iodobutane
Ans: 1 c, 2b, 3 c, 4c, 5 b
(VI) Read the passage given below and answer the following questions:
4
Within the 3d series, manganese exhibits
oxidation states in aqueous solution from +2 to +7, ranging from Mn2+(aq)
to MnO− 4 (aq). Likewise,
iron forms both Fe2+(aq) and Fe3+(aq) as well as the FeO2− 4 ion. Cr and Mn form oxyions
CrO2− 4 , MnO−
4 , owing to their willingness
to form multiple bonds . The pattern with the early transition metals—in the 3d series up
to Mn, and for the 4d, 5d metals
up to Ru and Os—is that the
maximum oxidation state corresponds to the number of ‘‘outer
shell’’ electrons. The highest oxidation states of the 3d metals may depend upon complex
formation (e.g., the stabilization of Co3+ by ammonia) or upon the pH (thus MnO
2− (aq) is prone to disproportionation in acidic solution). Within the 3d series, there is
considerable variation in relative stability of oxidation states, sometimes on moving from one metal
to a neighbor; thus, for iron, Fe3+ is more stable than Fe2+, especially in
alkaline conditions, while the reverse is true for cobalt. The ability of transition metals to exhibit a wide range
of oxidation states is marked with metals such as vanadium, where the standard potentials can be rather small,
making a switch between states relatively easy.
(Cotton, S. A. (2011). Lanthanides: Comparison to 3d
metals. Encyclopedia of inorganic and Bioinorganic Chemistry.)
In the following questions, a statement of assertion
followed by a statement of reason is given.
Choose the correct answer out of the following choices on the basis of the
above passage.
A. Assertion and reason both are correct statements and reason is correct explanation for assertion.
B. Assertion and reason both are correct statements but reason is not correct
explanation for assertion.
C. Assertion is correct statement but reason is wrong statement.
D. Assertion is wrong statement but reason is correct statement.
1. Assertion: Highest oxidation state is exhibited by transition metal
lying in the middle of the series.
Reason: The highest oxidation
state exhibited corresponds to number of (n-1)d electrons.
2. Assertion: Fe3+ is more stable than Fe2+
Reason: Fe3+ has 3d5 configuration while Fe2+ has 3d6 configuration.
3. Assertion: Vanadium had the ability to exhibit
a wide range of oxidation
states.
Reason: The standard potentials Vanadium are rather small, making a switch between oxidation states relatively easy.
4. Assertion: Transition metals like Fe, Cr and Mn form oxyions
Reason: Oxygen is highly electronegative and has a tendency to form multiple
bonds.
5. Assertion: The highest oxidation states of the 3d metals depends only on electronic configuration of the metal.
Reason: The number of electrons in the (n-1)d and ns subshells determine
the oxidation states
exhibited by the metal.
Ans: 1.c 2 a 3 a 4 b 5d
(VII) Read the passage given below and answer the following questions:
Reductive alkylation is the term applied to the process
of introducing alkyl groups into ammonia or a primary or secondary amine by means
of an aldehyde or ketone in the
presence of a reducing agent. The present discussion is limited to those
reductive alkylations in which the reducing
agent is hydrogen and a catalyst or "nascent" hydrogen, usually
from a metal- acid combination; most of these reductive alkylations have been
carried out with hydrogen and a catalyst. The principal variation excluded is
that in which the reducing agent is formic acid or one of its derivatives; this modification is known as the Leuckart
reaction. The process of reductive alkylation of ammonia
consists in the addition of ammonia to a carbonyl compound and reduction of the addition compound or its
dehydration product. The reaction usually is carried out in ethanol
solution when the reduction is to be effected catalytically
RCHO + NH3 RCHOHNH2
2[H]
RCH2NH2
2[H]
RCH= NH
Since the primary
amine is formed in the presence
of the aldehyde it may react in the same way as ammonia, yielding
an addition compound,
a Schiff's base (RCH= NCH2R) and finally, a secondary
amine. Similarly, the primary
amine may react with the imine,
forming an addition product
which also is reduced to a secondary amine Finally, the secondary amine may react with either the aldehyde or the
imine to give products which are reduced to tertiary amines.
RCH=NH + RCH2NH2 RCHNHCH2R 2[H] (RCH2)2NH + NH3 NH2
(RCH2)2NH + RCHO (RCH2)2NCHR
2[H] (RCH2)3N + H2O
OH
(RCH2)2N + RCH=NH (RCH2)2NCHR 2[H] (RCH2)3N + NH3
NH2
Similar reactions
may occur when the carbonyl compound employed
is a ketone.
(source: Emerson,
W. S. (2011). The Preparation of Amines by Reductive Alkylation. Organic Reactions, 174–255.
doi:10.1002/0471264180.or004.03 )
Q1. Ethanal on reaction with ammonia forms an imine (X) which on reaction with nascent hydrogen
gives (Y). Identify ‘X’
and ‘Y’.
A.
X is CH3CH=NH and Y is CH3NH2
B.
X is CH3CHOHNH2 and Y is CH3CH2NH2
C. X is CH3CHOHNH2 and Y is CH3NH2
D.
X is CH3CH=NH and Y is CH3CH2NH2
Q2. Acetaldehyde is reacted with ammonia followed
by reduction in presence of hydrogen as a catalyst.
The primary amine so formed further reacts with acetaldehyde. The Schiff’s base formed during the reaction
is:
A.
CH3CH=NHCH3
B.
CH3CH=NHCH2CH3
C.
CH3=NHCH2CH3
D. CH3CH2CH=NHCH3
Q3. The reaction of ammonia and its derivatives with aldehydes is called:
A.
Nucleophilic substitution reaction
B. Electrophilic substitution reaction
C. Nucleophilic addition reaction
D.
Electrophilic addition
reaction
Q4. (CH3CH2CH2)2NH + CH3CH2CHO P 2[H] Q
The compound
Q is:
A.
(CH3CH2CH2)3N
B.
(CH3CH2CH2)2N(CH2CH3)
C.
(CH3CH2)3N
D. (CH3CH2)2NH
Q5. Reductive alkylation
of ammonia by means of an aldehyde
in presence of hydrogen as reducing agents results in formation of:
A.
Primary amines
B.
Secondary amines
C. Tertiary amines
D.
Mixture of all three amines
(Ans: 1D,2B,3C,4 A,5D)
(VIII) Read the passage given below and answer the following questions:
Some colloids are stable by their nature, i.e., gels,
alloys, and solid foams. Gelatin and jellies are two common examples of
a gel. The solid and liquid phases in a gel are interdispersed with both phases being continuous. In most
systems, the major factor influencing the stability is the charge on the colloidal particles. If a particular ion is
preferentially adsorbed on the surface
of the particles, the particles in suspension will repel
each other, thereby
preventing the formation of
aggregates that are larger than colloidal dimensions. The ion can be either positive or negative depending on the
particular colloidal system, i.e., air bubbles accumulate negative
ions, sulphur particles have a net negative charge
in a sulphur sol, and the particles
in a metal hydroxide sol are positively charged. Accumulation of charge on a surface
is not an unusual phenomenon-dust is attracted to furniture surfaces by electrostatic forces. When salts
are added to lyophobic colloidal systems the
colloidal particles begin to form larger aggregates and a sediment forms
as they settle. This phenomenon is called flocculation, and the
suspension can be referred to as flocculated, or colloidally unstable. If the
salt is removed, the suspension can usually be restored to its original
state; this process
is called deflocculation or peptization. The original and restored colloidal
systems are called
deflocculated, peptized, or stable
sols.
Why
does a small amount of salt have such a dramatic effect on the stability of a
lyophobic colloidal system?
The answer lies in an understanding of the attractive and repulsive forces
that exist between colloidal particles. Van der Waals forces are
responsible for the attractions, while the repulsive forces
are due to the surface
charge on the particles. In a stable colloid, the repulsive forces are of greater
magnitude than the attractive forces. The magnitude of the electrical repulsion is diminished by addition of ionized salt, which allows the dispersed
particles to aggregate and
flocculate. River deltas provide an example of this behaviour. A delta is
formed at the mouth of a river
because the colloidal clay particles are flocculated when the freshwater mixes with the salt water of the ocean
(source: Sarquis,
J. (1980). Colloidal systems.
Journal of Chemical
Education, 57(8), 602. doi:10.1021/ed057p602 )
Q1. Gelatin is a colloidal system.
A.
Solid in solid
B.
Solid in gas
C. Liquid in solid
D. Liquid in gas
Q2.Colloidal solutions
are stable due to:
A.
presence of charges on the colloidal
particles
B.
formation of aggregates by colloidal particles
C. preferential adsorption on the surface
D.
preferential absorption on the surface
Q3. Settling
down of colloidal particles to form a suspension is called:
A.
flocculation
B.
peptization
C. aggregation
D.
deflocculation
Q4. When Van der Waals forces are greater than forces due to the surface charge on the particles,
A. flocculation occurs.
B. the colloid is stable.
C. peptization takes place.
D. deflocculation occurs.
Q5. The particles
in suspension will repel each other, thereby preventing the formation of aggregates that are larger than colloidal
dimensions. This statement
explains:
A.
formation of delta
B.
river water is a colloidal of clay particles
C. effect of salt on lyphobic
colloid
D.
phenomenon of flocculation
(Ans: 1C, 2C, 3A,4A,5B)
(IX) Read the passage given below and answer the following questions:
Industrially widely applied esterification reactions are commonly
catalysed using mineral
liquid acids, such as sulphuric
acid and p-toluenesulphonic acid. The catalytic
activity of homogeneous catalysts is high. They
suffer, however, from several drawbacks, such as their corrosive nature, the existence of side reactions, and the fact
that the catalyst cannot be easily separated
from the reaction mixture. The
use of solid acid catalysts offers an alternative and has received
a lot of attention in the past years. Solid
acid catalysts are not corrosive and, coated
onto a support, they can be easily reused. Examples of solid acid catalysts
used in esterification reactions
include ion-exchange resins , zeolites and
superacids like sulphated zirconia and niobium acid. Ion-exchange resins
are the most common heterogeneous catalysts used and have proven to be effective in liquid phase
esterification and etherification reactions. Because of their selective adsorption of reactants and swelling nature, these resins not only catalyse the esterification reaction
but also affect the equilibrium conversion. Shortcomings
include insufficient thermal resistance, which limits the reaction temperature
to 120 oC, preventing widespread use in industry. Zeolites, like Y, X, BEA, ZSM-5 and MCM- 41 offer an interesting alternative and
have proven to be efficient catalysts for esterification reactions. Zeolites have found wide application in oil refining,
petrochemistry and in the production of fine chemicals. Their
success is based on the possibility to prepare zeolites with strong Brønsted acidity that can be
controlled within a certain range, combined with a good resistance to high reaction temperatures.
In
this study, the activity of various commercial available solid acid catalysts
is assessed with respect to the esterification of acetic acid with butanol. The ion-exchange resins Amberlyst 15 and
Smopex-101, the acid zeolites H-ZSM-5, H-MOR, H-BETA and H-USY, and the solid
superacids sulphated zirconia and niobium acid are selected. Comparative
esterification experiments have been carried
out using the homogeneous catalysts
sulphuric acid, p- toluenesulphuric acid and a heteropolyacid
(HPA).
The
weight-based activity of the heterogeneous catalysts tested is maximum for Smopex101. The following table gives the activity of different catalysts
in the esterification reaction between
acetic acid and butanol
at 750C.
Here: kobs: observed reaction rate constant ( m3mol-1s-1) kc catalysed reaction rate constant (m3mol-1gcat-1s-1) Please note: k c = k obs/ amount (in g)
(source: PETERS,
T., BENES, N., HOLMEN, A., & KEURENTJES, J. (2006). Comparison
of commercial solid acid catalysts
for the esterification of acetic acid with butanol. Applied
Catalysis A: General,
297(2), 182–188. doi:10.1016/j.apcata.2005.09.00)
Q1. Which of the following are heterogeneous catalysts
for esterifctaion reaction:
A.
sulphuric acid and p-toluenesulphonic acid
B.
sulphuric acid and niobium acid
C.
p-toluenesulphonic acid and niobium acid
D.
niobium acid and sulphated
zirconia
Q2. Unit for observed rate constant for esterification reaction is m3mol-1s-1, so the reaction
is:
A.
zero order
B.
first order
C. second order
D. third order
Q3. The catalytic activity
of homogeneous catalysts
is high. The weight based activity of HPA is less than which of the following
heterogenous catalysts?
A.
Smopex-101
B.
Amberlyst 15
C. sulphated ZrO2
D. H-USY-20
Q4. The weight-based activity
of the heterogeneous catalysts tested decreases in the following order:
A.
Smopex-101 > Amberlyst 15 > sulphated
ZrO2 > H-USY-20
>H-BETA-12.5 > H- MOR-45 > Nb2O5 > H-ZSM-5-12
B.
Smopex-101 > Amberlyst 15 > sulphated
ZrO2 > H-USY-20
>H-BETA-12.5 > H- MOR-45 > H-ZSM-5-12> Nb2O5
C. Smopex-101 > Amberlyst
15 > sulphated ZrO2 > H-USY-20 >H-BETA-12.5 > Nb2O5> H-MOR-45
> H-ZSM-5-12
D.
Smopex-101 > sulphated ZrO2 > Amberlyst
15 > H-USY-20 >H-BETA-12.5 > H- MOR-45
> H-ZSM-5-12> Nb2O5
Q5. Catalysts
used in oil refining industry
are:
A.
ion exchange resins
B.
superacids
C.
zeolites
D.
mineral liquid acids
(ANS: 1D, 2C, 3A, 4A, 5C)
(X) Read the passage given below and answer the following questions:
Biopolymers are polymers that are generated
from renewable natural
sources, are often biodegradable and nontoxic. They can be produced by biological systems
(i.e. microorganisms, plants and animals),
or chemically synthesized from biological materials (e.g., sugars, starch,
natural fats or oils, etc.). Two strategies are applied in converting these raw
materials into biodegradable polymers: extraction of the native polymer from a
plant or animal tissue,
and a chemical or biotechnological route of monomer
polymerization. Biodegradable biopolymers (BDP) are an alternative to petroleum-based polymers
(traditional plastics). Some BDP degrade in only a few weeks, while the
degradation of others takes several
months. In principle
the properties relevant
for application as well as biodegradability are determined by the molecular
structure. According to the American
Society for Testing
and Materials, biopolymers are degradable polymers
in which degradation results from the action of naturally occurring
microorganisms such as bacteria, fungi and algae .
Polylactic
acid (PLA) is an example of biopolymer. It is a thermoplastic polyester.
Generally, there are two major routes to produce polylactic acid from the lactic acid (CH3CH(OH)- COOH)monomer. The first route involves
condensation–water removal by the use of solvent under high vacuum and temperature. This approach
produces a low to intermediate molar mass polymer.
An alternative method is to remove water under milder conditions, without solvent, to produce a cyclic intermediate
dimer, referred to as lactide. This intermediate is readily purified by vacuum distillation. Ring opening polymerization of the dimer is accomplished under heat, again without the
need for solvent. By controlling the purity of the dimer it is possible to produce a wide range of molar masses
.PLA is a good material for production of clothing, carpet tiles, interior
and outdoor furnishing, geotextiles, bags, filtration systems, etc.
The
primary biodegradability of PLA was tested using hydrolysis tests at various
composting temperatures and pH. It was demonstrated that composting is a useful method for PLA biodegradation. The degradation rate is very slow in ambient temperatures. A 2017 study found that at 25 °C in sea water, PLA showed no degradation over
a year. As a result, it is poorly degraded
in landfills and household
composts, but is effectively digested in hotter
industrial composts.
(source: Flieger,
M., Kantorová, M., Prell, A., Řezanka, T., & Votruba,
J.
(2003). Biodegradable plastics
from renewable sources.
Folia Microbiologica, 48(1),
27– 44. doi:10.1007/bf02931273 )
In the following questions, a statement of assertion
followed by a statement of reason is given.
Choose the correct answer out of the following choices on the basis of the
above passage.
A. Assertion and reason both are correct statements and reason is correct explanation for assertion.
B. Assertion and reason both are correct statements but reason is not correct
explanation for assertion.
C. Assertion is correct statement but reason is wrong statement.
D.
Assertion is wrong statement
but reason is correct statement.
Q1.Assertion: Biodegradable polymers degrade in few weeks. Reason: Microorganisms bring about degradation of biopolymers. Q2. Assertion: Lactic acid on polymerisation forms
Reason: PLA is used in producing
geotextiles.
Q3. Assertion: Lactic acid undergoes
condensation polymerisation Reason:
Lactic acid is a bifunctional monomeric unit.
Q4. Assertion: . The degradation of PLA is very slow in ambient temperature. Reason:
PLA is a thermoplastic.
Q5.Assertion: PLA is poorly degraded
in landfills.
Reason: The degradation rate of PLA is very slow in ambient temperatures.
(ANS: 1D, 2B, 3A,4B,5A)
(XI) Read the passage given below and answer the following questions:
In the last 10 years much has been learned about the molecular structure of elemental
sulfur. lt is now known that
many different types of rings are sufficiently metastable to exist at room temperature for several days. It is known that at high temperature, the equilibrium composition allows for a variety of rings
and chains to exist in comparable concentration, and it is known that at the boiling point and above, the vapor as
well as the liquid contains small species with three, four, and five atoms.
The sulfur atom has the same number of valence
electrons as oxygen. Thus, sulfur atoms S2 and
S3 have physical
and chemical properties analogous to those of oxygen
and ozone. S2 has a ground state
of 38 σ3s2σ⋆3s2σ3pz2π3px
2 = π3py2π*3px1 = π*3py1. S3 , thiozone has a well- known uv spectrum, and has a bent structure, analogous to its isovalent molecules 03,
SO2, and S20. The chemistry of the two elements, sulphur
and oxygen, differs
because sulfur has a pronounced tendency for catenation. The most frequently quoted explanation is based on the electron structure of the atom. Sulfur
has low-lying unoccupied 3d orbitals, and it is widely believed that the 4s and 3d orbitals
of sulfur participate in bonding in a manner
similar to the participation of 2s and 2p orbitals in carbon.
(source: Meyer, B. (1976). Elemental sulfur. Chemical
Reviews, 76(3), 367– 388. doi:10.1021/cr60301a003 )
In the following questions, a statement of assertion
followed by a statement of reason is given.
Choose the correct answer out of the following choices on the basis of the
above passage.
A. Assertion and reason both are correct statements and reason is correct explanation for assertion.
B.
Assertion and reason both are correct statements but reason is not correct
explanation for assertion.
C. Assertion is correct statement but reason is wrong statement.
D.
Assertion is wrong statement
but reason is correct statement.
Q1 Assertion:
Sulphur belongs to same group in the periodic table as oxygen.
Reason: S2 has properties
analogous to O2.
Q2. Assertion: Thiozone has bent structure like ozone. Reason:
Ozone has a lone pair which makes the molecule
bent. Q3. Assertion: S2 is paramagnetic in nature
Reason: The electrons
in π*3px and π*3py orbitals in
S2 are unpaired. Q4.Assertion: Sulphur has a greater
tendency for catenation than oxygen. Reason: 3d and 4s orbitals of Sulphur have same energy.
(ANS: 1B,2B, 3A,4C)
(XII) Read the passage given below and answer the following questions:
Adenosine
triphosphate (ATP) is the energy-carrying molecule found in the cells of all
living things. ATP captures chemical
energy obtained from the breakdown of food molecules and releases it to fuel other cellular processes. ATP is a
nucleotide that consists of three main structures: the
nitrogenous base, adenine; the sugar, ribose; and
a chain of three
phosphate groups bound to ribose. The phosphate tail of ATP is the actual power
source which the cell taps. Available
energy is contained in the bonds between the phosphates and is released
when they are broken, which occurs
through the addition of a water
molecule (a process called hydrolysis). Usually only the outer phosphate is
removed from ATP to yield energy; when this occurs ATP is converted to adenosine diphosphate (ADP), the form of the nucleotide having only two phosphates.
The
importance of ATP (adenosine triphosphate) as the main source of chemical
energy in living matter and its
involvement in cellular processes has long been recognized. The primary mechanism
whereby higher organisms, including humans, generate
ATP is through mitochondrial oxidative phosphorylation. For the majority of organs, the main
metabolic fuel is glucose,
which in the presence of oxygen undergoes
complete combustion to CO2 and H2O:
C6H12O6
+ 6O2 à 6O2 + 6H2O + energy
The
free energy (ΔG) liberated in this exergonic (ΔG is negative) reaction is partially trapped as ATP in two consecutive processes: glycolysis (cytosol)
and oxidative phosphorylation (mitochondria). The
first produces 2 mol of ATP per mol of glucose, and the second 36
mol of ATP per mol of
glucose. Thus, oxidative phosphorylation
yields 17-18 times as much useful
energy in the form of ATP as can be obtained from the same amount of glucose by glycolysis alone.
The efficiency of glucose metabolism is the ratio of amount of energy
produced when 1 mol of glucose oxidised in cell to the
enthalpy of combustion of glucose. The energy lost in the process
is in the form of heat. This heat is responsible for keeping us warm.
(source: Erecińska, M., & Silver, I. A. (1989).
ATP and Brain Function. Journal of Cerebral
Blood Flow & Metabolism, 9(1), 2–19. https://doi.org/10.1038/jcbfm.1989.2 and https://www.britannica.com/science/adenosine-triphosphate)
Q1. Cellular oxidation of glucose is a:
A.
spontaneous and endothermic process
B.
non spontaneous and exothermic
process
C.
non spontaneous and endothermic process
D.
spontaneous and exothermic process
Q2. What is the efficiency of glucose metabolism
if 1 mole of glucose
gives 38ATP energy?(Given: The enthalpy of combustion of glucose is 686 kcal, 1ATP= 7.3kcal)
A. 100%
B. 38%
C. 62%
D. 80%
Q3.Which of the following statement
is true?
A.
ATP is a nucleoside
made up of nitrogenous base adenine and ribose sugar .
B.
ATP consists the nitrogenous base, adenine and the sugar, deoxyribose.
C. ATP is a nucleotide which contains a chain of three phosphate
groups bound to ribose sugar.
D.
The nitrogenous base of ATP is the actual power source.
Q4. Nearly 95% of the energy released during cellular respiration is due to:
A.
glycolysis occurring
in cytosol
B.
oxidative phosphorylation occurring in cytosol
C.
glycolysis in occurring mitochondria
D. oxidative phosphorylation occurring in mitochondria Q5. Which of the following
statements is correct:
A.
ATP is a nucleotide
which has three phosphate groups while ADP is a nucleoside which three phosphate
groups.
B.
ADP contains a nitrogenous bases adenine, ribose sugar and two phosphate
groups bound to ribose.
C. ADP is the main source of chemical
energy in living matter.
D.
ATP and ADP are nucleosides which differ in number of phosphate groups.
(ANS: 1D,2B(Glucose catabolism yields a TOTAL of 38 ATP. 38 ATP x 7.3 kcal/mol
ATP = 262 kcal. Glucose
has 686 kcal. Thus the efficiency of glucose metabolism
is 262/686 x 100 = 38%. ) ,3C,4D,5B)
(XIII)
Read the passage given below and answer the following questions:
The transition metals when exposed to oxygen at low
and intermediate temperatures form thin,
protective oxide films of up to some thousands of Angstroms in
thickness. Transition metal oxides lie between the extremes of
ionic and covalent binary compounds formed by
elements from the left or right side of the periodic table. They range from metallic
to semiconducting and deviate
by both large and small degrees from stoichiometry. Since d- electron
bonding levels are involved, the cations exist in various valence
states and hence give rise to a large number of oxides. The crystal structures are often classified by considering a cubic or
hexagonal close-packed lattice of one set of ions with the other set of ions filling
the octahedral or tetrahedral interstices. The actual oxide structures, however,
generally show departures from such regular
arrays due in part to distortions caused
by packing of ions of different size and to ligand field effects. These distortions depend not only on the number of d-electrons but also on the valence
and the position
of the transition metal in a period
or group. (source:
Smeltzer, W. W., & Young, D. J. (1975). Oxidation
properties of transition metals. Progress in Solid State Chemistry, 10, 17-54.)
In the following questions, a statement of assertion
followed by a statement of reason is given.
Choose the correct answer out of the following choices on the basis of the
above passage.
A. Assertion and reason both are correct statements and reason is correct explanation for assertion.
B. Assertion and reason both are correct statements but reason is not correct
explanation for assertion.
C. Assertion is correct statement but reason is wrong statement.
D. Assertion is wrong statement but reason is correct statement.
1. Assertion: Cations of transition elements
occur in various valence states
Reason: Large number of oxides of transition elements are possible.
2. Assertion: Crystal structure
of oxides of transition metals often show defects. Reason:
Ligand field effect
cause distortions in crystal structures.
3. Assertion : Transition
metals form protective oxide films. Reason:
Oxides of transition
metals are always stoichiometric.
4. Assertion: CrO crystallises in a hexagonal
close-packed array of oxide ions with two out of every
three octahedral holes occupied by chromium ions.
Reason: Transition metal oxide may be hexagonal
close-packed lattice of oxide ions with metal ions filling the octahedral voids.
(ANS: 1 B , 2 A, 3C , 4D )
(XIV)
Read the passage given below and answer the following questions:
The d block elements are the 40 elements contained in the four rows of ten columns (3-12) in the periodic
table. As all the d block elements
are metallic, the term d-block
metals is synonymous. This set of d-block elements
is also often identified as the transition metals, but sometimes the group 12 elements (zinc, cadmium, mercury) are
excluded from the transition metals
as the transition elements are defined as those with partly filled d or f
shells in their compounds. Inclusion
of the elements zinc, cadmium
and mercury is necessary as some properties of the group 12 elements are
appropriate logically to include with a discussion of transition metal chemistry.
The term transition element
or transition metal appeared to derive from early studies
of periodicity such as the
Mendeleev periodic table of the elements. His horizontal table of the elements was an attempt to group the elements together so that the chemistry of elements might be explained and predicted. In this
table there are eight groups labeled I-VIII with each subdivided into A and B subgroups. Mendeleev recognized that certain
properties of elements in Group VIII are related to those of some of the elements in Group VII and those at the start
of the next row Group I. In that sense, these elements
might be described
as possessing properties transitional from one row of
the table to the next. (source: Winter, M. J. (2015). D- block Chemistry (Vol. 27). Oxford University Press, USA.)
In the following questions, a statement of assertion
followed by a statement of reason is given.
Choose the correct answer out of the following choices on the basis of the
above passage.
A. Assertion and reason both are correct statements and reason is correct explanation for assertion.
B. Assertion and reason both are correct statements but reason is not correct
explanation for assertion.
C. Assertion is correct statement but reason is wrong statement.
D. Assertion is wrong statement but reason is correct statement.
1.
Assertion: Group 12 elements
are not considered as transition metals.
Reason: Transition metals are those which have incompletely filled d shell in their compounds.
2.
Assertion: All d block elements are metallic in nature.
Reason: The d –block elements belong to Group3 -12 of the periodic
table. 3.Assertion : Group VII elements of Mendeleev periodic
table are transition elements.
Reason: Group I –VIII in Mendleev
periodic table is divided into two subgroups, A and B.
4.Assertion: Nickel is a transition element that belongs to group 10 and period 4 of the modern periodic
table.
Reason: Electronic configuration of Nickel is [Ar]183d84s2
(ANS: 1A, 2B, 3D,4A)
(XV) Read the passage given below and answer the following questions:
EVIDENCE FOR THE FIBROUS NATURE OF DNA
The
basic chemical formula of DNA is now
well established. As shown in Figure 1 it consists of a very long chain, the backbone of which
is made up of alternate sugar and phosphate groups,
joined together in regular 3' 5' phosphate
di-ester linkages. To each sugar
is attached a nitrogenous base, only four different
kinds of which are commonly found in DNA. Two of these---adenine and guanine--- are purines, and the other two thymine
and cytosine-are pyrimidines. A fifth base, 5-methyl
cytosine, occurs in smaller amounts in certain organisms, and a sixth, 5-hydroxy-methyl-cytosine, is
found instead of cytosine in the T even phages. It should be noted that the chain is unbranched, a consequence of
the regular internucleotide linkage. On the other
hand the sequence of the different nucleotides is, as far as can be ascertained, completely irregular. Thus,
DNA has some features which are regular, and some which are irregular. A similar conception of the DNA molecule as a long thin fiber
is obtained from physicochemical analysis involving sedimentation, diffusion, light
scattering, and viscosity
measurements. These techniques indicate that DNA is a very asymmetrical structure approximately 20 A wide and many thousands of
angstroms long. Estimates of its molecular weight currently center between 5 X 106 and 107 (approximately 3 x104 nucleotides). Surprisingly each of these measurements tend to suggest
that the DNA is relatively rigid, a puzzling
finding in view of the large number of single bonds (5 per nucleotide) in the phosphate-sugar back
bone. Recently these indirect inferences have been confirmed by electron microscopy.
Figure 1
( source: Watson, J. D., & Crick,
F. H. (1953, January). The structure of DNA. In Cold Spring Harbor symposia on quantitative
biology (Vol. 18, pp. 123-131). Cold Spring Harbor
Laboratory Press.)
1.
Purines present in DNA are:
A.
adenine and thymine
B.
guanine and thymine
C.
cytosine and thymine
D.
adenine and guanine
2. DNA molecule has internucleotide linkage
and sequence of the different nucleotides
A. regular , regular
B.
regular , irregular
C. irregular , regular
D.
irregular , irregular
3. DNA has a backbone
A.
phosphate -purine
B.
pyrimidines- sugar
C. phosphate- sugar
D. purine- pyrimidine
4. Out of the four different
kinds of nitrogenous bases which are commonly found in DNA,
has been replaced
in some organisms.
A. adenine
B. guanine
C. cytosine
D. thymine
(ANS 1D, 2 B, 3 C, 4 C )
(XVI) Read the passage given below and answer the following questions:
Polysaccharides may be very large molecules. Starch, glycogen, cellulose, and chitin are examples of polysaccharides.
Starch
is the stored form of sugars in plants and is made up of amylose and
amylopectin (both polymers of
glucose). Amylose is soluble in water and can be hydrolyzed into glucose units breaking glycocidic bonds, by the enzymes
α- amylase and β-amylase. It is straight chain
polymer. Amylopectin is a branched
chain polymer of several D-glucose molecules. 80% of amylopectin is present in starch.
Plants are able to synthesize glucose, and the excess glucose is stored as starch in different
plant parts, including roots and seeds. The starch that is consumed by animals is broken down into
smaller molecules, such as glucose. The cells can then absorb the glucose.
Glycogen
is the storage form of glucose in humans and other vertebrates, and is made up
of monomers of glucose. It is
structurally quite similar to amylopectin . Glycogen is the animal equivalent of starch. It is stored in liver
and skeletal muscles.
Cellulose
is one of the most abundant natural biopolymers. The cell walls of plants are
mostly made of cellulose, which
provides structural support to the cell. Wood and paper are mostly cellulosic in nature.
Like amylose,
cellulose is a linear polymer
of glucose. Cellulose
is made up of glucose
monomers that are linked by bonds between
particular carbon atoms in the glucose molecule.Every other glucose
monomer in cellulose is flipped over and packed tightly as extended long chains. This gives cellulose its rigidity and high
tensile strength—which is so important
to plant cells. Cellulose passing through our digestive system is called
dietary fiber. (Source: https://chem.libretexts.org)
1. In animals , Glycogen is stored in :
A.
Liver
B.
Spleen
C.
Lungs
D.
Small Intestine
2.
Amylose is :
A. straight chain , water insoluble
component of starch ,which constitutes 20 % of it .
B. straight chain , water soluble component of starch ,which constitutes 20 % of it.
C. branched chain , water insoluble
component of starch ,which constitutes 80 % of it .
D. branched chain , water soluble
component of starch ,which constitutes 80 % of it .
3.
Which biopolymer breaks down to release
glucose , whenever
glucose levels drop in Our body :
A.starch
B.
cellulose
C. chitin
D.
glycogen
4.
The linkages which join monosaccharides to form long chain polysaccharides :
A.
Peptide linkage
B.
Disulphide bonds
C.
Hydrogen bonds
D.
Glycosidic linkage
5. Cellulose on complete hydrolysis yields:
A. amylose
B. amylopectin
C. glucose
D. amylose and amylopectin
