4
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:

Blue litmus paper turns ____ on contact with an acidic solution.

 

A) green B) red
C) yellow D) brown
 
Answer & Explanation Answer: B) red

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Q:

What is the dominant chemical present in detergent powder?

 

A) Calcium carbonate B) Sodium alkyl sulphate
C) Hydrochloric acid D) Sodium carbonate
 
Answer & Explanation Answer: D) Sodium carbonate

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Q:

Nitrous Oxide' is the chemical name of ______.

 

A) Tear Gas B) Fire Extinguisher
C) Laughing Gas D) Mosquito Repellent
 
Answer & Explanation Answer: C) Laughing Gas

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Q:

_____ gases trap heat in the atmosphere which makes the Earth warmer, causing global warming.

 

A) Greenhouse B) Nobel
C) Elemental D) Compound
 
Answer & Explanation Answer: A) Greenhouse

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Q:

Calcium Sulphate dihydrate is commonly known as ________.

 

A) gypsum B) glass
C) asbestos D) limestone
 
Answer & Explanation Answer: A) gypsum

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Q:

What is the more common name for solid carbon dioxide?

 

A) Epsom B) Dry Ice
C) Potash D) Quick Silver
 
Answer & Explanation Answer: B) Dry Ice

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Q:

Which of the following is the major component of vinegar?

 

A) Citric acid B) Lactic acid
C) Nitric acid D) Acetic acid
 
Answer & Explanation Answer: D) Acetic acid

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Q:

When we cut an onion, the synthase enzyme converts the amino acid sulfoxides of the onion into which acid?

 

A) Sulfenic acid B) Citric acid
C) Nitric acid D) Sulphuric acid
 
Answer & Explanation Answer: A) Sulfenic acid

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