UNIT -1 SOLUTION
1
2
3.
4
5
6
7
8.
9.
10
Why is an increase in temp. observed on mixing chloroform with acetone.
On mixing equal volumes of water and ethanol,what type of deviation would you expect from Raoult’s law ?
Non ideal solution show either positive or negative deviations from Raoult’s law.What are these
deviations and why are they caused ? Explain with one example for each type.
Define the terms osmosis and osmotic pressure.Is osmotic pressure of a solution a colligative property ?
Explain.
Define the following terms: (i) Mole fraction (ii) Isotonic solutions (iii) Van’t Hoff factor (iv) Ideal solution.
Define an ideal solution and write one of its characteristics .
State Henry’s law.What is the effect of temperature on the solubility of a gas in liquid.
Account for the following :–
(a) CaCl2 is used to clear snow from roads in hill stations.
(b) Ethylene glycol is used as antifreeze solution in radiators of vehicles in cold countries.
(c) The freezing point depression of 0.01 m NaCl is nearly twice that of 0.01 m glucose solution.
Give reasons for the following :–
(a) RBC swell up and finally burst when placed in 0.1% NaCl solution.
(b) When fruits and vegetables that have been dried are placed in water, they slowly swell and return to
original form.
(c) A person suffering from high blood pressure is advised to take less amount of table salt.
What is meant by positive deviations from Raoult’s law ? Give an example.What is the sign of mixH
for positive deviation ?
[Delhi 2015 ]
11
Definr azeotropes. what type of azeotrope is formed by positive deviation from Raoult’s law ?
Give an example.
[Delhi 2015 ]
12
Calculate the freezing point depression expected for 0.0711 m aqueous solution of Na2SO4.If this solution
actually freezes at -0.320oC, what should be the value of the Van’t Hoff factor ?
( Kf for water is 1.86 oC mol1)
[Delhi 2009 ][ Ans : 0.397 K, 2.42]
13
A solution Prepared by dissolving 1.25 gm of oil of winter green ( methylsalicylate) in 99 gm of benzene
has a boiling point of 80.31 oC.Determine the molar mass of this compound.( B.P of pure benzene = 80.10oC)
and Kb for benzene = 2.53oCKgMol-1
[Delhi 2010 ]
14
Calculate the boiling point of a solution prepared by adding 15.00 gm of NaCl to 250 gm of water.
( Kb for water = 0.512 KKgmol-1. Molar mass of NaCl = 58.44 g)
[Delhi 2011 ]
15
Calculate the freezing point of an aqueous solution prepared by adding 10.50 g of MgBr2 in 200 gm of water.
( Molar mass of MgBr2 = 184 g, Kf for water = 1.86 K Kg mol-1 )
[Delhi 2011 ]
16
A solution is prepared by dissolvung 8.95 mg of a gene fragment in 35.0 ml of water has an osmotic pressure
of 0.335 torr at 25oC.Assuming the gene fragment is a non electrolyte.determine its molarmass.
[Delhi 2011 ]
17
What would be the molar mass of a compound if 6.21 g of it dissolved in 24.0 gm of chloroform form a
solution that has a boiling point of 68.04oC.The boiling point of the pure chloroform is 61.7oC and the
boiling point elevation constant, Kb for chloroform is 3.63oC/m.
[Delhi 2011 ]
18
A 1.00 molal aqueous solution of trichloro aceticacid ( CCl3COOH) is heated to its boiling point.The soln.
has the boiling point of 100.18 oC .Determine the van’t Hoff factor for trichloroacetic acid
( Kb for water = 0.512 K Kg mol-1)
[Delhi 2012 ]
19
15.0 g of an unknown molecular material was dissolved in 450 gm of water. The resulting solution was found
to freeze at -0.34 o C.What is the molecular mass of this material. ? ( Kf for water = 1.86 K Kg mol-1)
[Ans 182 gm mol-1] [Delhi 2012 ]
20
18 g of glucose, C6H12O6 ( molar mass = 180 g mol-1) is dissolved in 1 kg of water in a sauce pan.
At what temperature will this solution boil ?
( Kb for water = 0.52 K Kg mol, boiling point of water = 373.15 K)
[ Ans. 373.202K]
21
Determine the osmotic pressure of a solution prepared by dissolving 2.5× 10 2 g of K2SO4 in 2 L water
at 25oC, assuming that it is completely dissociated.
( R = 0.0821 Latm K-1mol1 , Molar mass of K2SO4 = 174 gmol1 )
[ Ans. 5.27× 10 3 atm]
22
Calculate the mass of a compound ( Molar mass = 256 gm mol-1) to be dissolved in 75 gm of benzene
to lower its freezing point by 0.48 K ( Kf = 5.12 K Kg mol-1)
23
3.9 g of benzoic acid dissolved in 4.9 g of benzene shows a depression in freezing point of 1.62 K.
Calculate the van’t Hoff factor and predict the nature of solute ( associated or dissociated).
[ Given : Molar mass of benzoic acid = 122 g mol-1 , Kf for benzene = 4.9 K Kgmol-1]
24
(a) Calculate the freezing point of solution when 1.9 g of MgCl2 ( M = 95 gmol-1) was dissolved in 50 g
of water, assuming MgCl2 undergoes complete ionization.
( Kf for water = 1.86 K Kg mol-1 )
(b) (i) Out of 1M glucose and 2M glucose , which one has higher boiling point and why ?
(ii)
What happens when the external pressure applied becomes more than the osmotic pressure
of the solution ?
OR
(a)
(b)
when 2.56 g of sulphur was dissolved in 100 g of CS2, the freezing point lowered by 0.383 K.
Calculate the formula of sulphur ( Sx)
Blood cells are isotonic with 0.9 % sodium chloride solution.What happens if we place blood
cells in a solution containing
(i)
1.2 % sodium chloride solution ?
(ii)
0.4 % sodium chloride solution ?
UNIT -2 ELECTROCHEMISTRY
Q.1
(a) Define the molar conductivity of a substance and describe how for weak and strong electrolytes, molar
conductivity changes with concentration of solute.How is such change explained ?
(b) A voltaic cell is set up at 25oC with the following half cell:
Ag+ ( 0.001M) | Ag and Cu2+ (0.10 M) | Cu
What would be the voltage of this cell ? ( Eo cell = 0.46 V )
[ Ans: 0.312 V] [ Delhi 2009 ]
Q.2
(a) Define the term molar conductivity.How is related to the conductivity of the related solution ?
(b) One half cell in a voltaic cell is constructed from a silver wire dipped in silver nitrate solution of unknown
concentration.Its other half cell consists of zinc electrode dipping in 0.1 M solution of Zn(NO3)2.A voltage
1.48 V is measured for this cell.use this information calculate the conc. if silver nitrate solution used.
Given Eo Zn2+ | Zn = - 0.763 V
Eo Ag+ | Ag = 0.80 V
[Ans. : 0.04M][ Delhi 2009 ]
Q.3
(a) State Kohlrausch’s law of independent migration of ions.Write an expression for the molar conductivity
of acetic acid at infinite dilution acoording to Kohlrausch’s law.
(b) Calculate the mo for aceticacid.
mo (HCl) = 426 S cm2 mol1
mo (NaCl) = 126 S cm2 mol1
mo (CH3COONa) = 91 S cm2 mol1
[ Delhi 2010 ]
Q.4
Calculate the potential for the half cell containing 0.10 M K2Cr2O7 (aq), 0.20 M Cr3+(aq) and 1.0 × 104 M H+(aq)
The half cell reaction is
Cr2O72(aq) + 14 H+ (aq) + 6 e
2Cr3+ + 7 H2O (l)
and the standard cell potential is given as Eo = 1.33 V
[Ans: 0.76 V] [ Delhi 2011 ]
(a) What type of a battery is the lead storage battery ? Write the anode and the cathode reactions and the overall
reaction occuring in a lead storage battery when current is drawn from it.
(b) In the button cell, widely used in watches, the following reaction takes place
Zn (s) + Ag2O(s) + H2O(l)
Zn2+(aq) + 2Ag (s) + 2OH
o
Determine Eo and G for the reaction.
(Given Eo Zn2+ | Zn = - 0.763 V
Eo Ag+ | Ag = 0.80 V )
[ Delhi 2012 ]
Q.5
Q.6
Q.7
Q.8
Q.9
(a)Define the molar conductivity of a solution and explain how molar conductivity change with change in conc.
of a solution for weak and a strong electrolyte.
(b) The resistance of a conductivity cell containing 0.001 M KCl solution at 298 K is 1500 What is the cell
constant if the conductivity of 0.001 M KCl solution at 298 K is 0.146 × 103 S cm1 ?
[Ans:
0.219 cm1] [ Delhi 2012 ]
Calculate the emf of the following cell at 298 K :
Fe(s)|Fe2+(0.001M)|| H+( 1 M)| H2(g) ( 1 bar), Pt
( Given Eo cell = 0.44 V)
[Ans:
0.5285V]
[ Delhi 2013 ]
The conductivity of 0.20 M solution of KCl at 298 K is 0.025 S cm-1.Calculate its molar conductivity.
[Ans:
125 S cm2 mol1]
[ Delhi 2013 ]
(a) Define the following
(i)
Limiting molar conductivity
(ii)
Fuel cell
(b)
Resistance of a conductivity cell filled with 0.1 mol L KCl solution is 100  .If the resistance of the
–1
same cell when filled with 0.02 mol L KCl solution is 520  calculate the conductivity and molar
conductivity of 0.02 mol L KCl solution. The conductivity of 0.1 mol L KCl solution is 1.29 × 102 S cm1
–1
–1
–1
[ Delhi 2014 ]
Q.10
(a)
(b)
State the Faraday’s first law of electrolysis.How much charge in terms of faraday is required for the
reduction of 1 mol of Cu2+ to Cu.
Cal the emf of the following cell at 298 K
Mg(s)|Mg2+(0.1M)|| Cu2+( 0.01 M)| Cu (s)
( Given Eo cell = 2.71 V , 1 F = 96500 C Mol)
[ Delhi 2014 ]
Q.11
(a)
Following reactions occur at cathode during the electrolysis of aqueous silver chloride solution:
Ag+ (aq)
+
e-
Ag(s)
Eo = 0.80 V
H+(aq)
+
e-
1/2 H2 (g)
Eo = 0.00 V
On the basis of their standard reduction electrode potential ( )values, which reaction is feasible
at cathode and why ?
(b)
Q.12
Define limiting molar conductivity .Why conductivity of an electrolyte solution decrease
with decrease in concentration.
[ Delhi 2015 ]
Calculate the emf of the following cell at 298 K :
Fe(s)|Fe2+(0.001M)|| H+( 0.01 M)| H2(g) ( 1 bar), Pt
( Given Eo Fe2+ | Fe = - 0.44 V
Eo H+ | H2 = 0.00 V
)
[ Delhi 2015 ]
Q.13
Calculate the e.m.f of the cell at 298 K:
2Cr(s) + 3Fe2+(0.1M)
2Cr3+(0.01M) + 3Fe
3+
2+
given: E°(Cr |Cr) = 0.74 V, E°(Fe | Fe) = 0.44 V
[ Delhi 2016 ]
Q.14
From the given cells:
Lead storage cell, Mercury cell, Fuel cell and Dry cell
Answer the following :
(i)
Which cell is used in hearing aids ?
(ii)
Which cell was used in apollo space programme ?
(iii)
Which cell is used in automobiles and invertors ?
(iv)
Which cell does not have long life ?
Q.15
Calculate the degree of dissociation () of acetic acid if its molar conductivity (m) is 39.05 S cm2mol–1.
Given o(H+) = 349.6 S cm2 mol–1 and o(CH3COO–) = 40.9 S cm2 mol–1
[ Delhi 2017 ]
Q.16
(a)
(b)
Q.18
(a)
Calculate the mass of Ag deposited at cathode when a current of 2 amperes was passed through
a solution of AgNO3 for 15 minutes.
(Given : Molar mass of Ag = 108 g mol–1 1F = 96500 C mol–1)
Define fuel cell.
[ Delhi 2017 ]
When a bright silver object is placed in the solution of gold chloride, it acquires a golden tinge but
nothing happens when it is placed in a solution of copperchloride. Explain this behavior of silver.
[Given : ECu2+/Cu = + 0.34 V; Eo Ag+/Ag = + 0.80 V, EoAu3+/Au = + 1.40 V]
[ Delhi 2017 compt. ]
Q.19
(b)
Consider the figure given above and answer the following questions :
(i) What is the direction of flow of electrons ?
(ii) Which is anode and which is cathode ?
(iii) What will happen if the salt bridge is removed ?
(iv) How will concentration of Zn2+ and Ag+ ions be affected when the cell functions ?
(v) How will concentration of these ions be affected when the cell becomes dead ?
OR
(a) What is limiting molar conductivity ? Why there is steep rise in the molar conductivity of weak
electrolyte on dilution ?
(b) Calculate the emf of the following cell at 298 K :
Mg(s)| Mg2+ (0.1 M)|| Cu2+ (1.0 × 10–3 M)| Cu(s) [Given = Eocell = 2.71 V]
(a)
Write the cell reaction and calculate the e.m.f of the following cell at 298K:
Sn(s)|Sn2+(0.004M)|| H+( 0.020 M)| H2(g) ( 1 bar), Pt
( Given Eo Sn2+ | Sn = - 0.14 V
Eo H+ | H2 = 0.00 V
(b)
(i)
(ii)
(a)
(b)
)
[ Ans: E = 0.1105 V]
Give reasons:
On the basis of Eo values, O2 gas should be liberatedat anode but it is Cl2 gas which is liberated
in the electrolysis of aqueous NaCl.
Conductivity of CH3COOH decrease on dilution.
OR
For the reaction
2 AgCl (s) + H2 (g) ( 1 atm)
Go = - 43600 J at 25 oC
Calculate the emf of the cell
Define fuel cell and write its two advantages.
2Ag(s) +
2H+( 0.1M) +
2 Cl(0.1M)
[ E = 0.344 V]
[ Delhi 2018]
Q.20
Eo for the given redox reaction is 2.71 V
Mg (s) +
Cu2+ ( 0.01 M)
Mg2+ ( .001M) + Cu (s)
Calculate Ecell for the reaction.Write the direction of flow of current when an external opposite potential
applied is
(i)
less than 2.71 V and
[ Delhi 2019][ Ecell = 2.7395 V]
(ii)
greater than 2.71 V
OR
(a)
A steady current of 2 amp was passed through two electrolytic cells X and Y connected in series
containing electrolytes FeSO4 and ZnSO4 until 2.8 g of Fe deposited at the cathode of the cell X.
How long did the current flow ?Calculate the mass of Zn deposited at the cathode of the cell Y.
( Molar mass : Fe = 56 g mol1, Zn = 65.3 g mol1, 1 F = 96500 C mol1)
(b)
In the plot of molar conductivity (m ) vs square root of concentration ( C1/2) , following curves are
obtained for two electrolytes A and B:
Answer the following :
(i)
Predict the nature of electrolytes A and B
(ii)
What happens on extrapolaration of molar
conductivity m to concentration approaching
A
zero for electrolytes A and B ?
m
B
[ Delhi 2019][ t = 4825 s / 80.417 min, m Zn = 3.265 g]
C
1/2
UNIT -3 CHEMICAL KINETICS
1.
List four factors which affect the rate of a chemical reaction. State how each of these factors changes the
reaction rate.
2.
Differentiate between
(a) Average rate and instantaneous rate of a chemical reaction.
(b) Rate of a reaction and specific rate of reaction.
3
The rate constant for a reaction of zero order in A is 0.0030 mol L-1 s-1.How long will it take for the initial
concentration of A to fall from 0.10 M to 0.075 M ?
[ Delhi 2010 ]
4
A first order reaction is 15% completed in 20 minutes.How long will it take to 60% completion?
[Ans: 112.7min.]
5
A first order reaction is 40% completed in 50 minutes.How long will it take to 80% completion?
[Ans: = 157.6 min.]
6
Calculate the two- third life of a first order reaction having K = 5.48×10-14 s-1
7
A reaction is first order in A and second order in B.
(i) Write the differential rate equation.
(ii) How is the rate affected on increasing the concentration of B three times?
(iii) How is the rate affected when the concentrations of both A and B are doubled?
\8
What do you understand by the ‘order of reaction’ Identify the reaction order from each of the following
units of reaction rate constant: (i) L-1 mol s-1 (ii) Lmol-1s-1
[ Delhi 2012 ]
9
The rate of a reaction triples when temperature changes from 20° to 50° C. Calculate the energy of
activation for such reaction (R = 8.314J K-1 mol-1)
[Ans: 28.8kjmol-1]
10
For a reaction the energy of activation is zero.What is the value of rate constant at 300K if,
k=1.6 × 106 s-1 at 280K
11
Rate constant k of a reaction varies with temperature according to the equation
log k = constant - 2.303EaRT where Ea is the energy of activation for thr reaction. When a graph is
plotted for log k versus 1/T, a straight line with a slope - 6670 K is obtained. Calculate the energy of
activation for this reaction. State the units (R = 8.314JK-1mol-1)
[Ans: 127711.4 J mol-1]
[Ans: 2.01×1013 s]
12
(a)
A reaction is second order in A and first order in B
(i)
Write the differential rate equation.
(ii)
How is the rate affected on increasing the conc. of A three times ?
(iii)
How is the rate affected when the conc. of both A and B are doubled ?
(b)
A first order reaction takes 40 minutes for 30 % decomposition.Calculate t1/2 for this reaction.
( Given log 1.428 = 0.1548)[ Ans: t1/2 = 77.7 min ]
(a)
(b)
OR
For a first order reaction, show that the time required for 99% completion is twice the time
required for the completion of 90% of reaction.
Rate constant ‘k’ of a reaction varies with temperature ‘T’ according to the equation
log k = log A 
Ea
1
2.303 R T
Where Ea is the activation energy.When a graph is plotted for log k Vs 1/T , a straight line
with a slope of - 4250 K is obtained.Calculate the ‘Ea’ for the reaction.
( R = 8.314 JK-1mol-1)
[ Ans: 81.375 Kjmol-1]
[ C.B.S.E 2013]
Q.13
For the hydrolysis of methyl acetate in aqueous solution, the following results were obtained:
t/s
[CH 3COOCH3]
0
0.60
30
0.30
60
0.15
(i) Show that it follows pseudo first order reaction, as the concentration of water remains constant.
(ii) Calculate the average rate of reaction between the time interval 30 to 60 seconds.
(Given log 2 = 0.3010, log 4 = 0.6021)
[ Delhi
Q14
(a)
For a reaction A + B
2015 ]
P, the rate is given by
Rate = k[A][B]2
(i)
(ii)
(b)
Q 15
How is the rate of reaction affected if the concentration of B is doubled
What is the overall order of reaction if A is present in large excess ?
A first order reaction takes 30 minutes for 50% completion. Calculate the time required
for 90% comple tion of this reaction. (log 2 = 0.3010)
[ Delhi 2015 ]
For a reaction : 2NH3(g)
N2(g) + 3H2(g)
Rate = k
(i)
(ii)
Q 16
Write the order and molecularity of this reaction.
Write the unit of k.
[ Delhi
2016 ]
The rate constant for the first order decompostition of H2O2 is given by the following equation :
log k = 14.2 - (1.0 ×10 )
T
K
Calculate Ea for this reaction and rate constant k if its half-life period be 200 minutes.
(Given R = 8.314 J K-1 mol-1)
[ Delhi
2016 ]
Q.17
Following data are obtained for the reaction :
N2 O 5
2NO2 + ½O2
t/s
0
300
600
–1
–2
–2
[N2O5]/mol L
1.6 × 10
0.8 × 10
0.4 × 10–2
(a) Show that it follows first order reaction.
(b) Calculate the half-life. (Given log 2 = 0.3010 log 4 = 0.6021)
[ Delhi 2017, t1/2 = 300 s]
Q.18
[ Delhi 2017comt, First order, sec1]
Q.19
The following data were obtained during the first order thermal decomposition of SO2Cl2 at a constant volume :
Experiment
Time (s)
Total pressure (atm)
1
0
0.4
2
100
0.7
Calculate the rate constant (k)
[Given : log 2 = 0.3010; log 4 = 0.6021]
[Delhi 2017 compt. Ans: 1.39×10   sec1]
Q.20 For the reaction
2 N2O5(g)
4 NO2 (g)
+
O2 (g)


1 .
the rate of formation of NO2(g) is 2.8 ×10 M sec .Calculate the rate of disappearance of N2O5(g)
Q.21
Q.22
Q.23
[ 1.4×10   M sec1 ]
A first order reaction is 50% completed in 40 minutes at 300 K and in 20 min. at 320 K.
Calculate thw activation energy of the reaction.
( Given : Log2 = 0.3010, log4 = 0.6021, R = 8.314 JK-1mol-1)
[Delhi 2018 Ans: 27663.8 J / mol]
The decomposition of NH3 on platinum surface is zero order reaction. If rate constant k is 4 × 10–3 M s–1
how long will it take to reduce the initial concentration of NH3 from 0.1 M to 0.064 M. ?
[Delhi 2019] [ t = 9 sec ]
For a reaction:
2H 2O 2
2 H2O + O2
the proposed mechanism is as given below:
(1)
H2O2 + I
H2O + IO ( Slow)
(2)
H2O2 + IO
H2O + I+ O2
(i)
(ii)
(iii)
Write rate law for the reaction
Write the overall order of the reaction.
Out of steps (1) and (2) which one is rate determining step ?