Acid/Base

[Temperature101]

Advertisement - Members don't see this ad

A compound with which of the following atoms would be the STRONGEST base?

A. A weakly electronegative atom carrying a negative charge
B. A highly electronegative atom carrying a negative charge
C. A weakly electronegative atom carrying no charge
D. A highly electronegative atom carrying no charge

Why A is better answer than C?

 

[Captain Sisko]

A compound with which of the following atoms would be the STRONGEST base?

A. A weakly electronegative atom carrying a negative charge
B. A highly electronegative atom carrying a negative charge
C. A weakly electronegative atom carrying no charge
D. A highly electronegative atom carrying no charge

Why A is better answer than C?

Use conjugate acid stability and examples to check your work. NH2- is more basic than NH3, right?

 

[circulus vitios]

It's been like 3 years since I've taken gen chem...why isn't B the best answer?

edit: Never mind, I think I get it. We want an anion with the electrons held loosely so they would be more likely to act as a nucleophile.

 

[LoLCareerGoals]

Or think of it in terms of charge affinity. Strong base wants some protons.

Weakly el-neg particles do not like carrying neg charge.
Weakly neg with no charge is like: "Fine by me".
Weakly neg with neg charge: "Don't really like this neg charge, I could really use some protons".
Strongly el-neg with no charge: "I could really use some el-ons or shed some protons, to get neg."
Strongly el-neg with neg charge: "Sweet..."

 

[Balantidiumcoli]

The answer is A

To simplify it, think of the conjugate acids of those solutions and pKa.

Let highly electronegative atom be Cl and let weakly electronegative atom be C

A. CH3- + H -> CH4 (Highest pKa)
B. Cl- + H -> HCl (Low pKa)
C. CH4 + H -> CH5+ (Impossible)
D. Cl + H (not very reactive) -> HCl (Low pKa)

The higher the pKa of the conjugate acid is the more equilibrium lies in that direction.

-Edit- Did not see the answers posted in the original post as white.