P Block Elements: Chemistry Entrance

 

Q.1. Which of the following is a tetrabasic acid ?

A) Orthophosphoric acid

B) Hypo phosphorous acid

C) Metaphosphoric acid

D) Pyrophosphoric acid

Explanation-

Pyrophosphoric acid : 

(Tetrabasic)  

Q.2. When ammonia is passed over heated copper oxide, the metallic copper is obtained, The reaction shows that ammonia is

A) A dehydrating agent

B) An oxidizing agent

C) A reducing agent

D) A nitrating agent

Explanation-

 

Q.3.  Which is the most amphoteric oxide ?

A) NaO

B) MgO

C) AlO

D) CaO

Explanation-

Oxide of aluminum is amphoteric in nature, whereas NaO, MgO and CaO are basic in nature.

Q.4. Which of the following statements is incorrect  ?

A) BF  is the weakest Lewis acid 

B) Ammonal is a mixture of aluminium compounds and is used in bombs 

C) BF exists as dimer 

D) BCI  does not conduct electricity in its molten state 

Explanation-

 BF exists as dimer.

Q.5.  Orthoboric acid contains 

A) Pyramidal   units

B) Linear   units 

C) T-shaped   units 

D) Triangular   units    

Explanation-

Orthoboric acid  contains triangular  units joined together through H-bonding forming a trigonal planar layer structure.

Q.6. Aluminum deposited as vapors on glass forms a good mirror, essentially because 

A) It has better shine than Ag

B) It does not scratch

C) Coating is  much smoother

D) It does not tarnish in air

Explanation-

Aluminum being passive metal does not tarnish in air.

Q.7. In the electrolytic extraction of aluminum fused cryolite is added

A) To make a conduction solution of bauxite

B) To act as reducing agent

C) To increase Al production

D) To protect the anodes

Explanation-

Addition of cryolite to fused alumina during electrolytic extraction make the solution more conducting and low melting.

Q.8.  Which of the metal chlorides has maximum covalent character ?

A) NaCl

B) AlCl

C) CsCl

D) BaCl 

Explanation-

 has minimum size and maximum charges, hence forms compound with maximum covalent character among given choice. The covalent character of chlorides increases along a period and decreases down a group according of Fajan's rule.

Q.9. When concentrated  is heated with , brown fumes evolve. These fumes are due to

A) 

B) 

C) 

D)  

Explanation-

 

Q.10. Which one of the following elements is most metallic ?

A) P

B) As

C) Sb

D) Bi

Explanation-

Metallic character increases down the group.

Kinetic Theory Of Gases : Physics Entrance Exam

 

Q.1.  If k is the Boltzmann constant , the average kinetic energy of a gas molecule at absolute temperature T is 

A) k T/2

B) 3 k T/4

C) k T

D) 3 k T/2

Q.2. At room temperature (27C ) the rms speed of the molecules of a certain diatomic gas is found to be 1920 ms.The  gas is 

A) H

B) F

C) O

D) CI 

Explanation-

We know that  which gives 

 Since  M = 2 , the gas is hydrogen .

Q.3.  If a g as has f degrees of freedom, the ratio  of the gas is 

A) 

B) 

C) 

D)  

Explanation-

We know that  = no . of degress of freedom x molar gas constant / 2 or 

Q.4.  Two ideal gases at absolute temperature T and T are mixed . There is no loss of energy in this process . If n and n are the respective number of molecules of the gases , the temperature of the mixture will be 

A) 

B) 

C) 

D)  

Explanation-

Q.5.  Four molecules of a gas have speeds 1,2,3 and 4 km  . The value of the root mean square speed of the gas molecule is 

A)  

B) 

C) 

D)  

Explanation-

The rms speed = 

Q.6.   The average kinetic energy of a molecule of a gas at absolute temperature T is proportional to 

A) 1/T

B) 

C) T

D) T 

Explanation-

The average kinetic energy of a molecule of a gas at absolute temperature T is given by .

Q.7.  The root mean square speed of the molecules of a gas at absolute temperature T is proportional to 

A) 1/T

B) 

C) T

D) T 

Explanation-

The root mean square speed of the molecules of a gas is given by .

Q.8.    and  respectively represent the average kinetic energy of a molecule of oxygen and hydrogen. If the two gases are at the same temperature , which of the following statements is true ?

A)   >  

B)   =  

C)   <  

D)  Nothing can be said about the magnitude of   and  as the information given is insufficient  

Explanation-

The average kinetic energy of molecule =  kT which is independent of the molecular mass .

Q.9.  The temperature of an ideal gas is increased from 120 K to 480 K. If at 120 K , the root mean square speed of the gas molecules is v , then at 480 K it will be 

A) 4 v

B) 2 v

C) 

D)  

Explanation-

 . 

Q.10.  A vessel contains 1 mole of O gas ( molar mass 32 ) at a temperature T . The pressure of the gas is P . An identical vessel containing one mole of He gas ( molar mass 4 ) at a temperature  2 T has a pressure of 

A) 

B) P

C) 2 P

D) 8 P

Explanation-

For a gas , PV = nRT . Hence 

                   ( P )