Question

"Which of the following would be the best conductor of an electric current:
(a) 0.1 mol L-1 HNO3
(b) 0.1 mol L-1 NH3
(c) 0.1 mol L-1 H3PO4
(d) 0.1 mol L-1 CH3COOH"
How and why???

Answer 1

What do you think?

Answer 2

The conductivity depends on two mail factors:
Type of atoms (only charged stuff or metals can conduct)
Concentration (in out case is always the same).

As you can see at the pag 15 of this book http://www.bas.bg/cleps/poemes/eschool/conduction_of_electricity.pdf
The conducibility of a proton is higher than of the OH- group. So we can say that B. NH3 which in water gives us OH- and NH4 will not conduct as well as the stuff that leaves protons.

Answer 3

when an ionic compound dissolves in water, the positive and negative ions originally present in the crystal lattice persist in solution. Their ability to move nearly independently through the solution permits them to carry positive or negative electrical charges from one place to another. Hence the solution conducts an electrical current.

Answer 4

Ch3cooh is a weak electrolyte, its ability to conduct current is lowest.

Answer 5

And if we anlyze the last 3 molecule a,c,d, we can see that ch3cooh -> ch3coo- is the slowest.
In the table we have no mesurment for PO4-.

Answer 6

NH3 (nopes), HNO3nopes)
H3PO4 which seems to be the most powerful conductor of current within all compounds. Not only it will produce ions with water because it has three hydrogen atoms

Answer 7

Right, but it can be also be explained by the Kc, more something get dissosiated more stuff we have in solution.

Answer 8

I still don't understand how to tell. I know that it isn't CH3COOH because it only partially dissociates but I am confused with the other three..

Answer 9

Ok, maybe the table with the conductivity it was too confusing.

As we conductivity depends on ions (all that molecule dissosiated in ions in water), and as we have the same amouth on every molecule, we need to look how they dissociated. If it if a strong or a weak acid. So you need to look at the dissosiation table and compare the constant of dissosiation of each acid.

Answer 10

https://www.google.it/search?q=dissociation+constant+of+acid+table&newwindow=1&espv=2&tbm=isch&tbo=u&source=univ&sa=X&ved=0CCEQsARqFQoTCLiFu7qIv8cCFQjFFAod4ocFCg&biw=1280&bih=675#imgrc=gxxMH4CVm2fV8M%3A

Answer 11

Sorry, I'm in year 11 and we haven't learned about the table yet and the constants.

Answer 12

hey,
We know weak acid and weak bases are known as weak electrolytes right?
we all know acetic acid is a very weak acid hence it dissociates partially in water right? So that one we can take it out. Acetic acid is CH3COOH
H3PO4 is also out as it is a weak acid. Remember how it dissociates in water? It has 3 Ka values right?
NH3 is a weak base as we know hence that is also out. If it was a strong base like NaOH it does conducts electricity but here it is a weak electrolyte. So we are left with HNO3
HNO3 is a strong acid. So it is strong electrolyte. I hope you got it !
Refer this for knowledge about electrolytes. http://www.wou.edu/las/physci/poston/ch221/pdf/Acids-and-Bases.pdf

Answer 13

That does make more sense thank you! What does 3 Ka values mean?

Answer 14

Basically strong acids and strong bases are know as strong electrolytes and weak acids and weak bases are known as weak electrolytes. !

Answer 15

H3PO4 Ionizes in water in this way right ?
H3PO4 ------> H+ + H2PO4-

H2PO4--------------> H+ + HPO42-

HPO4----->2 H+ + PO43- Im sorry all the arrows should be the reversible arrows !
Just forget about the Ka values remember it like it dissociates 3 times to be fully ionized ! :)

Answer 16

Ok, I will. Thank you!

Answer 17

Anytime :)