How do you determine the order of least to most basic in the following

[CrazCo]

HCO3-, F-, I- and LiH.

 

I do not know how to approach it.

 

I could guess, but I have no method of finding this.

Edited November 17, 2010 by CrazCo

[mississippichem]

Remember that the conjugate base of a weak acid is a strong base. Inversely, the conjugate base of a strong acid is a weak base.

 

-One of the bases you listed is the conjugate base of a very strong acid...that means that species is a very weak base.

 

-The conjugate acid of [ce]HCO_{3}^-^[/ce] is [ce]H_{2}CO_{3}[/ce] is that a strong acid, a weak acid, or a "stronger-weak" acid?

 

-One of the species you listed yields a quite basic metal hydroxide in aqueous solution. Think about the Arrhenius definition of a base.

 

-You could always look up a table of [math]pK_{a}[/math] values if you know what those are.

[CrazCo]

Remember that the conjugate base of a weak acid is a strong base. Inversely, the conjugate base of a strong acid is a weak base.

 

-One of the bases you listed is the conjugate base of a very strong acid...that means that species is a very weak base.

 

-The conjugate acid of [ce]HCO_{3}^-^[/ce] is [ce]H_{2}CO_{3}[/ce] is that a strong acid, a weak acid, or a "stronger-weak" acid?

 

-One of the species you listed yields a quite basic metal hydroxide in aqueous solution. Think about the Arrhenius definition of a base.

 

-You could always look up a table of [math]pK_{a}[/math] values if you know what those are.

 

 

Thanks!

 

So hydrofluoric acid is a weak acid, therefore F- is a strong base!

Hydroiodic is a strong acid, therefore I- is a weak base!

Carbonic acid is a weak acid, therefore HCO3- is a strong base!

I am not sure about LiH, but I don't know how to determine whether HF is weaker or stronger than HCO3-

Edited November 18, 2010 by CrazCo

[mississippichem]

Thanks!

 

So hydrofluoric acid is a weak acid, therefore F- is a strong base!

Hydroiodic is a strong acid, therefore I- is a weak base!

Carbonic acid is a weak acid, therefore HCO3- is a strong base!

 

Yeah you've got it. But be careful with the terms strong and weak, something can only be truly strong if it dissociates into its constituent ions 100% in aqueous solution. So [ce]HCO_{3}^{-}[/ce] is technically not a strong base but it is a "stronger-weak base", same goes for [ce]F^{-}[/ce].

 

I am not sure about LiH, but I don't know how to determine whether HF is weaker or stronger than HCO3-

 

Here's a hint: [ce]HF[/ce] is one of the strongest of the common weak acids.

Edited November 18, 2010 by mississippichem

[CrazCo]

Yeah you've got it. But be careful with the terms strong and weak, something can only be truly strong if it dissociates into its constituent ions 100% in aqueous solution. So [ce]HCO_{3}^{-}[/ce] is technically not a strong base but it is a "stronger-weak base", same goes for [ce]F^{-}[/ce].

 

 

 

Here's a hint: [ce]HF[/ce] is one of the strongest of the common weak acids.

 

Thanks!

 

Does this look good?

 

Least to Most Basic: I-,F-, HCO3- LiH

[mississippichem]

Thanks!

 

Does this look good?

 

Least to Most Basic: I-,F-, HCO3- LiH

 

Yep, good job...rep it

Edited November 18, 2010 by mississippichem