Solutions @Class 11 physical chemistry revision problems for competitions pArt-1


What is bond order of CO+ ?

Answer- 3.5


Why N2 is almost inert but CO is very reactive although both have triple bonds?

Answer- HOMO of N2 is sigma BMO 2pz, hence strongly bonded valence electrons. Whereas HOMO of CO is sigma ABMO 2s, hence its valence electrons are easy to lose/are reactive.


All ionic compounds are water soluble (T/F). Give examples.

Answer- False; BaSO4,CaCO3 etc are ionic but water insoluble.


Why AgBr or AgI are colored even if they are diamagnetic substances ?

Answer- greater polarisation


Compare melting point of SnCl2, SnCl4

Answer- SnCl4 being more covalent has Lesser melting point.


Which species has strongest H-bonding ?



Which oxidising agent is stronger than F2? (given in ncert exercises of redox reactions)

Answer- Na4XeO6


What is hybridisation of BORON in Borax? (refer ncert p block for structure)

Answer-sp2, sp3


What is equivalent Mass of NaOH in reaction; Br2 + NaOH = NaBr + NaBrO3?

Answer- 12*M/1o


What is pH of mixture of 100 ml 0.1 M CH3COOH and 40 ml 0.1 M NaOH?

Answer- 4.74 + log 2/3


What is pH of mixture of 100 ml 0.1 M H2C2O4 and 100 ml 0.1 M NaOH?

Answer-(pKa /2)


What is pH of Na2HPO4 (aq) if successive dissociation constants of H3PO4 are x,y and z respectively?

Answer- (y+z)/2


Which of following are buffer?

(A) CH3COOH + NaOH (1:1 ratio)
(B) CH3COOH + NaOH (2:1 ratio)
(C) CH3COOH + NaOH (1:2 ratio)
(D) CH3COONa + NaOH (1:1 ratio)

Answer- C


Which of following are buffer?

(A) CH3COONa + HCl (1:1 ratio)
(B) CH3COONa + HCl (1:2 ratio)
(C) CH3COONa + HCl (2:1 ratio)
(D) CH3COOH + CH3COONa (1: 15 ratio)

Answer- A, C


Which of following are buffer?

(A) CH3COONH4 (aq)
(B) Na2B4O7.10H2O (aq)
(C) aq (NH4)2C2O4
(D) aq NaHCO3



Solubility of AgCl in water is increased in presence of
(A) NH3 (aq)
(B) KCN (aq)
(C) Hypo solution
(D) CH3NH2 (aq)



Solubility of Al(OH)3 in water is increased in presence of
(A) HCl (aq)
(B) NaOH (aq)
(C) excess water
(D) NaCl (aq)



Which has maximum number of atoms?
(A) 1 g O
(B) 1 g O2
(C) 1 g O3
(D) 1 g CO

Answer-A=B=C < D


Vapor density of a gaseous mixture of NO2 and N2O4 is 38. What is Weight percentage of NO2 in mixture?

Answer- (w/46) + [(100-w)/92]= 100/(2*38)


Which is more concentrated aqueous solution , 1 molar or 1 molal ?

Answer- 1 molar


What is ratio of time periods of revolution of two electrons revolving around nucleus in different orbits of radius R and 4R respectively?

Answer- 1:8


Consider a hypothetical atom called “positronium”, having “positron” at nucleus instead of a proton, and an electron revolving around nucleus; What is value of
(A) Rydberg constant
(B) energy of first orbit
(C) radius of first orbit
(D) speed of electron on first orbit

Answer-(A) R/2, (B) (13.6eV)/2 , (C) 2*(0.529 nm) (D) 2.18* 10^6 m/s


Consider, the hypothesis that under New definitions, angular Momentum quantum number takes values from 0,1,2,… Upto n.
Under this hypothesis,
(A) How many unpaired electron would be in Fe (26)?
(B) How many elements will be present in second and third period respectively?
(C) what will be position of element Fe(26) in periodic table?

Answer -(A)  2,  (B) 8, 18 (C)1S2, 1p6, 2S2, 2p6,  3s2, 2d8; 3rd period, d block, group 10


Which of following Transition will be in visible region?

(A) 2->1 in Hydrogen spectrum
(B) 2->1 in Helium monopositive ion spectrum
(C) 3->2 in He+ spectrum
(D) 4->3 in He+ spectrum

Answer- D


What is position of radial node of 2s orbital of hydrogen atom?
(A) a0
(B) 0.5 * a0
(C) 2 a0
(D) 4 a0
[Here, a0 is Bohr’s radius or radius of first Bohr’Orbit]

Answer- C


dz2 is considered as Combination of
(A) dx2 – dy2 and dz2 – dy2
(B) dx2 – dz2 and dz2 – dy2
(C) dz2 – dy2 and dz2 – dx2
(D) dy2 – dz2 and dz2 – dy2



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