2
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:

The percentage of nitrogen in the air is about

A) 74% B) 76%
C) 78% D) 80%
 
Answer & Explanation Answer: C) 78%

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3 531
Q:

Methane contributes towards global warming so it is called a _________________ gas.

 

A) poisonous B) carcinogenic
C) infectious D) greenhouse
 
Answer & Explanation Answer: D) greenhouse

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2 3019
Q:

Which of the following is a metal?

 

A) Sulphur B) Nitrogen
C) Oxygen D) No option is correct
 
Answer & Explanation Answer: D) No option is correct

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1 2174
Q:

Which of the following group is NOT Dobereiner Triads?

 

A) Li, Na, K B) N, P Au
C) Cl, Br, I D) Ca, Sr, Ba
 
Answer & Explanation Answer: B) N, P Au

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2 7572
Q:

Safety matches contain

A) Sulphur B) Phosphorus
C) Magnesium D) Potassium
 
Answer & Explanation Answer: B) Phosphorus

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2 480
Q:

Air ___________________ are the substances which contaminate the air.

A) Reactants B) Irritants
C) Resistants D) Pollutants
 
Answer & Explanation Answer: D) Pollutants

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2 458
Q:

By using which foam the Researchers from Indian Institute of Technology – Bombay have made a low cost piezo resistive vibration sensor?

A) Only Polyurethane B) Only Polyethylene
C) Both Polyurethane and Polyethylene D) Neither Poly urethane nor Polyethylene
 
Answer & Explanation Answer: B) Only Polyethylene

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3 495
Q:

Which of the following is NOT a compound?

 

A) Ammonia B) Milk
C) Sodiumchloride D) Chalk
 
Answer & Explanation Answer: B) Milk

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