3
Q:

Which of the following is the strongest base?

A) LiCH3 B) LiF
C) LiOH D) LiNH2

Answer:   A) LiCH3



Explanation:

The stability of the ions is determined by the energy of the lone pairs. Carbon has the least effective nuclear charge (Zeff) and so the lone pair on the CH3− ion has the highest energy, making it the least stable ion and so the strongest base. The Zeff increases as we move across the period until we get to fluorine which has the greatest Zeff and so its lone pairs have the lowest energy, making F− the least basic ion.

 

In order of decreasing basicity they are ranked LiCH3 > LiNH2 > LiOH > LiF. We are dealing with the ions F−, OH−, NH2− and CH3− and so the factor which influences their basicity is the stability of the ion compared to its conjugate acid.

Subject: Chemistry
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Q:

Which of the following is used to remove the green colour from glass?

 

A) Manganese dioxide B) Sulphur dioxide
C) Titanium dioxide D) Silicon dioxide
 
Answer & Explanation Answer: A) Manganese dioxide

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1 2967
Q:

Which of the following statement(s) is/are CORRECT?

 

I. Carbon compounds linked by only single bond are called saturated compounds.

II. Carbon compounds having double or triple bonds are called unsaturated compounds.

III. Saturated carbon compounds are more reactive than unsaturated carbon compounds.

 

A) Only I and II   B) Only I and III  
C) Only II and III   D) All I, II and III  
 
Answer & Explanation Answer: A) Only I and II  

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Q:

What is the maximum number of electrons that the  outermost shell can have?

 

A) 2 B) 6
C) 8 D) none
 
Answer & Explanation Answer: C) 8

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3 2541
Q:

The first electron shell which is the nearest to the nucleus never holds more than 'n' electrons, where 'n' is equal to:

 

 

A) 8 B) 4
C) 6 D) 2
 
Answer & Explanation Answer: D) 2

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3 771
Q:

What is the atomic mass of Zirconium?

 

A) 91.22 B) 89.22
C) 88.22 D) 90.22
 
Answer & Explanation Answer: A) 91.22

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Q:

How many types of isotopes does Scandium have?

 

A) 9 B) 7
C) 10 D) 13
 
Answer & Explanation Answer: D) 13

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Q:

Which of the following has the lowest melting point?

 

A) Zinc B) Silver
C) Lead D) Tin
 
Answer & Explanation Answer: D) Tin

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Q:

What is the bond angle (in degrees) in the structure of a benzene molecule?

 

A) 60   B) 150  
C) 90   D) 120
 
Answer & Explanation Answer: D) 120

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