final revision module for chemistry

| BAN SAL CLASSES ^ TARGET IIT JEE 2007

PHYSICAL CHEMISTRY XII & XIII

FINAL PRA CTICE PROBLEMS FOR IIT JEE-2007

(With Answers)

ALL THE BEST FOR JEE -2007

Q. 1 Wave number of the second line of Paschen series of hydrogen atom is (RH = 109700 cm !) (A) 18750 A (B) 3452 A (C) 7801 A (D) 1542656 A

Q.2 Radiation corresponding to the transition n = 4 to n = 2 in hydrogen atoms falls on a certain metal (work function = 2.0 eY). The maximum kinetic energy of the photoelectrons will be (A) 0.55 eV (B) 2.55 eV (C) 4.45 eY (D) none

Q.3 The maximum number of electrons in a subshell having the same value of spin quantum number is given by (A) 1 + 2 (B) 21 + 1 (C) 2(2/+1) (D) None

1 Q.4 When a graph is plotted with log (Keq) v/s —, then intercept on log (Keq) axis will be

AH° AH0 AS° AS o

( A ) T ^ T (B)-TTT^r ( Q — (D) 2.303R v 7 2.303RT R v ' 2.303R

Q.5 For the synthesis of NH3 from the Haber process starting with stoichiometric amount of N2 and H2, the attainment of equilibrium is predicted by which curve:

N2(g) + 3H2(g) >2NH,(g)

t: t; Nil,

(A) NH3 ( C ) l N ft (D)L I)' ' Hn 2

-NI I,

- N 2 -H,

Q.6 The reaction A(g) + B(g) ^ C(g) + D(g) is elementry 2nd order reaction opposed by elementry second order reaction. When started with equimolar amounts of A and R, at equilibrium, it is found that the conc. of Ais twice that of C. Specific rate for forward reaction is 2 x 10"3 mol 1 Lsec!. The specific rate constant for backward reaction is (A) 5.0 x 10"4 M"1 sec"1 (B) 8 x 10"3 M"1 sec"1

(C) 1.5 x 102 M 1 sec"! (D) none of these

Question No. 7 to 8 ( 2 questions) A 0.5 L reaction vessel which is equipped with a movable piston is filled completely with a IM aqueous solution of H202 .The H202 decomposes to H20 and 02(g) in a first order process with half life 10 hrs at 300 K. As gas decomposes, the piston moves up against constant external pressure of 750 mm Hg.

Q.7 What is the net work done by the gas from the start of sixth hour till the end of 10 hrs? (A) 100 J (B) 120 J (C) 130 J (D) 150 J

Q.8 If AH for decomposition of H202(aq.) is X K J/mole, how much heat has been exchanged with surrounding to maintain temperature at 300 K (in KJ) from the start of 6th hour till the end of 10th

hour. (A) -0.1035 X (B)-0.2070 X (C)-0.052 X (D) 0.026 X

Q.9 During study of a liquid phase reaction A (aq) > B (aq) + C (aq) the variation in concentration of B with time is given

t/min 0 10 20 30 oo conc. (B) mole/L 0 0.1 0.19 0.271 1 The initial rate of reaction was? (A) 1.76 x lo-4 M sec"1 (B) 2.76 x lO^M sec"1

(C) 3.86 x iO^M sec-1 (D) 2 xio^Msec-1

(feBansal Classes Problems for JEE-2007 [7]

Q.IO

Q.ll

Q . 1 2

Q.13

Q.14

Q.15

Q.17

Q.18

A catalyst increases the (A) rate of forward reaction only (B) free energy change in the reaction (C) rates of both forward and reverse reactions (D) equilibrium constant of the reaction

The conductance of a salt solution (AB) measured by two parallel electrodes of area 100 cm2 separated by 10 cm was found to be 0.0001 Q_1. If volume enclosed between two electrode contain 0.5 mole of salt, what is the molar conductivity(Scm2mol_1) of salt at same conc. (A) 0.01 (B) 0.02 (C) 2 x 10"5 (D) none of these

X Y -

X

400cm 2

10cm

Arrange the following electrolytes in the increasing order of coagulation power for the coagulation of A S 2 S 3 solution. (I) Na3P04 (II) MgCl2 (III) A1C13

( A ) I < II < III (B) III = II < I (C) I <111 < 1 1 (D) III < I < II

If Pd v/s P (where P denotes pressure in atm and d denotes density in gm/L) is plotted for H2 gas

d (ideal gas) at a particular temperature. If

(A) 40 K (B) 400 K

dP (Pd)

P=8.21atm

(C) 2 0 K

10, then the temperature will be

(D) none

A sample of phosphorus that weighs 12.4 gm exerts a pressure 8 atm in a 0.821 litre closed vessel at 527°C. The molecular formula ofthe phosphorus vapour is (A)P2 ( B ) P 4 (C)P6 (D)Pg

For a gas deviation from ideal behaviour is maximum at (A) 0°C and 1.0 atm (B) 100°C and 2.0 atm (C) -10°C and 1.0 atm (D) - 1 0 ° c a n d 4 0 a t m

Q.16 An ideal gaseous mixture of ethane (C2H6) and ethene (C2H4) occupies 28 litre at STP. The mixture reacts completely with 128 gm 0 2 to produce C02 and H2Q. Mole fraction at C2H6 in the mixture is (A) 0.6 (B) 0.4 (C) 0.5 (D) 0.8

100 cm3 of a solution of an acid (Molar mass = 82) containing 39 gm of the acid per litre were completely neutralized by 95.0 cm3 of aq. NaOH containing 20 gm of NaOH per 500 cm3. The basicity of the acid is (A) 1 (B) 2 (C) 3 (D) data insufficient

SPM i ^ 0.2 M a q . ; 0 , 1 5 M a q . NaCl Solution I CaCl-, Solution

Study the following figure and choose the correct options. (A) There will be no net moment of any substance across the membrane (B) CaCL will flow towards the NaCl solution. (C) NaCl will flow towards the CaCl2 solution. (D) The osmotic pressure of 0.2 M NaCi is lower than the osmotic pressure of 0.15 M CaCl2,

assuming complete dissociation of electrolyte.

Q.19 What is [Ag' J in a solution made by dissolving both Ag2Cr04 and Ag2C204 until saturation is reached with respect to both salts. Ksp(Ag2C204) = 2 x 10 n , Ksp(Ag2Cr04) :

(A) 2.80 x 10-4 (B) 7.6 x 10"5 (C) 6.63 x !0"6 " (D) 3.52 x x 10 ! 2


0,20 A3B2 is a sparingly soluble salt of molar mass M (g moH) and solubility x g lit-1. The ratio ofthe molar concentration of B3~ to the solubility product of the salt is

x5 1 M4 1 M4

Q.21 A 1 litre solution containing NH4C1 and NH4OH has hydroxide ion concentration of 10~6 mol/lit. Which of the following hydroxides could be precipitated when the solution is added to 1 litre solution of 0.1 M metal ions i Ag(OH) (Ksp = 5 x lCr3) II Ca(OH)2 (Ksp = 8 x l (r6) ffl Mg(OH)2 (Ksp = 3 x 1CT11) IV Fe(OH)2 (Ksp = 8 x 10"16) (A) I, II, IV " (B) IV (C) III and IV (D) II, III, IV

Q.22 From separate solutions of four sodium salts NaW, NaX, NaY and NaZ had pH 7.0, 9.0, 10.0 and 11.0 respectively. When each solution was 0.1 M, the strongest acid is: (A) HW (B) HX (C) HY (D) HZ

Q.23 AG for the conversion of 2 mol of C6H6(f) at 80°C (normal boiling point) to vapour at the same temperature and a pressure of 0.2 atm is (A) -9.44 Kcal/mol (B) -2.27 Kcal/nioi (C) -1.135 Kcal/moi (D) zero

Q.24 A certain ideal gas has Cvm = a + bT, where a = 25.0 J/(mol. K) and b = 0.03 J (mol.K2), Let 2 mole of this gas go from 300 K and 2.0 litre volume to 600 K and 4.0 litre. AS,,.,. is gdS (A) 32.08 J/K (B)-1-2 08 J/K (C) 64.17 J/K (D) None

Q.25 What is ArG (KJ/mole) for synthesis of ammonia at 298 K at following sets of partial pressure:

N2(g) + 3H2(g) ^ 2NH3(g); ArG° = -33 KJ/mole. [Take R = 8.3 J/K mole, log2 = 0.3; log3 = 0.48]

Gas N2 H, NH3

Pressure (atm) 1 3 0.02

(A)+ 6.5 (B) - 6.5 (C) + 60.5 (D)-60.5 Q.26 Give the correct order of initials T (true) or F (false) for following statements.

(I) Two electrons in the same atom can have the same set of three quantum numbers (II) The lowest energy configuration for an atom with electrons in a set of degenerate orbital s

is that having the maximum number of unpaired electrons with the same spin.

(III) The value of (PV) / (RT) at critical state is 0.325

Tr 8 (IV) The ratio of Critical Constants -—- is ———

p Rxb r c (A) TTFF (B) FTFT (C)FFTT (D) TTTF

Q.27 Give the correct order of initials T (true) or F (false) for following statements. (i) The ratio of the radii of the first three Bohr orbit of hydrogen atom is 1 : 8 : 27

(ii) Am (molar conductivity) for a strong electrolyte decreases as the electrolyte concentraton increases.

(iii) The frequency of a green light is 6 x io14 Hz, then its wavelength is 500 nm

(iv) The mass of an equivalent of H3P04 when it combines with NaOH using the equation H3PG4 + 2NaOH > Na2HP04 + 2H20 is 49 g.

( A)FFTT (B) FTFT * (C) TFTF (D)FTTT

^Bansa I Classes Problems for JEE-2007 [4]

Q.28 Give the correct order of initials T (true) or F (false) for following statements I. An azeotropic solution of two liquids has a boiling point lower then either of them

when it shows negative deviation from Raoult's Law. II. The fraction of volume occupied by atoms in a body centered cubic unit cell is 0.74. III. In the face-centered cubic unit cell of closest packed atoms, the radius of atoms in terms

V'3a of edge length (a) of unit cell is ——

IV. If the anions (Y) form hexagonal closest packing and cations (X) occupy only 2/3 octahedral voids in it, then the general formula of the compound is X0Y3(present in 2 : 3).

(A)FFFT (B)FFTT (C) TFFT ' (D) TTFF

Q.29 Which of the following statement(s) is/are correct:

Statement (a) : For the reaction Br, + QH~ > B r + BrOT + H2G, The equivalent weight of

3M Br2 is - y where M = Molecular weight.

Statement (b) : For an aqueous solution to be neutral it must have pH = 7 Statement (c) : For the reaction

1 1 — N2 + NO equilibrium constant is KL

and 2NO ^ N2 + (X equilibrium constant is K2

then K2. KL = 1 Statement (d) : If the partial orders are equal to corresponding coefficients in the balanced reaction,

the reaction must be elementary (simple) (A) Statement a (B) Statement b, d (C) Statement a. b, d (D) All

Q.30 Give the correct order of initials T (true) or F (false) for following statements. I. If the equilibrium constants for the reaction Br, ^ 2Br at 500 K and 700 K are 10"10 and

10~5 respectively, then reaction is exothermic. II. When a solution prepared by mixing 90 ml of HQ solution (pH = 3), 10 mi solution of

NaOH (pH = 11) and 60 ml water will be 3.1.

III. In the nuclear reaction p 5 U » 7 Pb. the total number of a and (3 particles lost would

b e l l . IV. An aqueous solution of an alcohol (B P 56°C) in water (B.P. 100°C) has vapour pressure

more than that of water. (A)TFTT (B)FFFT (C) FFTF (D)FFTT


ANSWER

Q.l

Q.2

Sol.

Q.3 Q.4 Q.5 Q.6

Sol.

Q.7 Sol.

V = - = R t _1 1_ 32 _ 52 y = 7801 cm"1

A

13.6 13.6 13.6 En = - eV ; E2 = - ; = eV/atom

AE = E4 - E2 = 2.55 eV Absorbed energy = work function of metal + K.E.

2.55 = 2 + K.E. K.E. = 0.55 eV Ans.

B D A B k

= k k e£i K b

/

eq

c At the end of 5 hours

A A °

at the end of 10th hours

\ , 2 = ~

\,2

2

An Ar V2-1 0 1 ~ 2 ~ V2

=> 0.2071 mole/L amount decayed in 0.5 L = 0.2071/2

moles of 0 2 formed = ~ (

Aq = 0 . 2 0 7 ^

f 0.2071^ 0.2071" I 2 j 4 mole

Q.8

Sol.

Q . 9

Q.10 Q.ll

W = -PAV = -nRT = - (0.2071/4) x 8.314 x 300 = -129.14 Joule A

^0.2071 Heat exchanged (q )

A C B

x AH = -0.1035 X kJ/mole

Sol. G* / 10

a 100 0.1 ; G = 0.0001 S ; V = 100 x 10= 1000 cm3 = 1 litre

K X I O O ( 0 . l x 0 . 0 0 0 1 ) x 1 0 0 0

M 0 . 5

K = G G * = 0. x 0.0001 = 10-5

= 0.02 Scm2 moH Ans.


Q.12 Sol.

Q.13 Sol.

As2S3 is negativley charged sol., so coagulation power Al3+ > Mg2+ > Na+

A PM = dRt

f \ M V RT J

d(Pd) _ 2PM dP ~ RT

10 2x8.21x2 0.0821xT

= 10

Q.14 Q.15 Q.16 Sol.

T = 40 K

B D B C2H6 + 3.5 0 2 -> 2C02 + 3H20 ; C2H4 + 30 , -> 2C02 + 21^0 Let vol. of ethane is x

22.4 x 4 = 3.5 x + 3 ( 2 8 - x ) 89.6 = 3.5 x + 84 - 3x x = 11.2 litrE

at const. T & PV a n Mole fraction of C2H6 in mixture 11.2

28 xlOO = 0.4

Q.17 Sol.

B meq" + acid = meqn of base Acid: 3.9 gm acid present in 100 cm3

Base: 20 gm NaOH present in 500 cm3

NIV,=N2V2

3 9 f 20 x 1000 = 95 x I xlOO

(—) I n J V40500 n = 2

Q.18 Sol.

Q.19

Sol.

D 7tj = ij x CjRT ; 7t2 = i2 x C2RT [only solvent (H20) molecules can passed through SPM]

= 2 x 0.2RT; =3xO."l5RT h<n2 D

Ag2Cr04 (s) ^ 2Ag+ (aq) + CrO2" (aq)

2x + 2y x

Ag2C204(s) ^ 2Ag+(aq) + C 2 0 2 - (aq)

2y + 2x y

K s p , x 2x10" x —— = - = ; t=> - =0.1 Kso y 2x l0 _ y

2 x 10"11 = (2x + 2y)2.y = (2.2y)2.y 2 x 10~n = 4.84 y3

y= 1.6 x 10"4

x = 0.16 x 10"14

Total (Ag+) = 2x + 2y = (2 x 0.16 + 2 x 1.6) x 10^ = 3.52 x 10"4 Ans.


Q.20 C Sol. Solubility S = x/M

A 3 B 2 ( S ) ^ 3 A 2 " ( a q ) + 2 B 3 " ( a q )

3 S 2 S

, „ . [ A 3 - ] 2 S 1 1 M 4

K s p = ( 3 S ) W =» JOBS' ; L - J - ^ =» ^

Q . 2 1 B

Sol. when 1 litre each are mixed [OH"] = 10"6 M (Buffer solution) Mn+ = 0.05 M for M2+ = Q = [0.5][10-6]2 = 5 x 10~14

Q > Ksp only for Fe2+

only Fe(OH)2 is ppt. Q . 2 2 A

Q . 2 3 B

Sol. C6H6(/) -> C6H6(g) At 1 atm, AG = 0 we know for reversible processes, dG = VmdP - SdT (Gibbs equation)

dT = 0, dG = VmdP for a reaction, d(AG) = n(AVm)dP (for n moles)

P 2 P 2

Jd(AG) - n j(AVm)dP; Pt = 1 atm and P2 = 0.2 atm Pi Pi

n = 2 and, AVm = V g - V g = ~

? R T H P AG0.2 atm - AG, a t m = n J ^ ^ A G1 atm = 0

1

0.2 => AG0 2 atm - 2 x RT In — = - 2.27 Kcal/mol

Q.24 C , r nCvdT r dT „ f ( a + bT)dT „ f R J W n r (25 + 0.03T)dT

Sol. jds = J — + j nR — = 2j — + 2J - d V = 2j i — ' — + 2R^n2

= 2[25 ^n2 + 0.03 [T2 - TJ ] + 2Rin2 => 2[25 x 0.693 + 0.03 x 300] + 2 x 8.314 x 0.693 = 52.65 + 11.52

AS = 64.17 J/k Q . 2 5 D

Sol. AG = AG0 + RT In P 2

NH3

Pn2xPH2

(0.02) AG = -33000+ 8.314 x 2.303 log f - = - 60.5 kJ/mole

1x3 Q.26 A Q.27 D Q.28 A Q.29 A Q.30 D


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