Which Acid Has the Strongest Conjugate Base and Which is the Strongest Acid?

[Soaring Crane]

1. Which Bronsted-Lowry acid has the strongest conjugate base?

a. HBr
b. HClO4
c. HF
d. HI

2. What is the strongest acid among the following?

a. HF
b. HCl
c. HBr
d. HI


Correct?
Thanks.

 

[Astronuc]

These might help

http://en.wikipedia.org/wiki/Conjugate_acid
http://en.wikipedia.org/wiki/Acid-base_reaction_theories

http://en.wikipedia.org/wiki/Strong_acid
http://en.wikipedia.org/wiki/Weak_acid

http://en.wikipedia.org/wiki/Strong_base
http://en.wikipedia.org/wiki/Weak_base

Another useful site
http://www.nyu.edu/classes/tuckerman/honors.chem/lectures/lecture_21/node7.html

 

[ksinclair13]

Number two is incorrect. The higher the electronegativity of X in HX, the stronger the acid. However, an exception to this is fluorine, which is the point of the question. Following this, what do you think the answer is?

 

[Soaring Crane]

According to my text, the size of X increases from F to I, so acidity increases from HF to HI since the H-X bond strength decreases as you go down the group.

Therefore, shouldn't my answer be correct? HI is stronger than the other three?

If the elements of binary acids were in the same ROW, then increasing electronegativity indicates higher acid strength.

 

[siddharth]

Therefore, shouldn't my answer be correct? HI is stronger than the other three?

Yes, you are right.

For the first one, you need to find the weakest acid (weaker the acid, stronger the conjugate base).

 

[ksinclair13]

I apologize. My teacher must've made a mistake when he taught us that (he only mentioned it a few times in class). I will have to talk to him about that tomorrow.

 

[Soaring Crane]

Well, HF is the weakest acid, so my answer is correct for #1?

 

[siddharth]

Yes, I think that's right as well.