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 -
1
sec-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.,
rate = k CAα CBβ (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.
1. Assertion: Rate of reaction is a measure of change in concentration of reactant with
respect to time.
Reason: Rate of reaction is a measure of change in concentration of product with
respect to time.
2. Assertion: For a reaction: P +2Q 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
(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 -
1
sec-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.,
rate = k CAα CBβ (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.
1. Assertion: Rate of reaction is a measure of change in concentration of reactant with
respect to time.
Reason: Rate of reaction is a measure of change in concentration of product with
respect to time.
2. Assertion: For a reaction: P +2Q 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
