[4evrastudent]

I was looking for some help with an electrochem question, shown below:

"A current of 0.25 A is passed through 400 mL of a 2.00 M solution of NaCl for 35.0 minutes. What will be the pH of the solution after the current is turned off?"

First off, I want to know how many moles are in this solution so I can use that as a conversion factor later on if necessary.
2.0 mol / 1000 mL = .40 mol / 200 mL = .80 mol / 400 mL

I figure a good next step is writing the chemical equation.
NaCl  Na⁺ + Cl^-
I also know that in my chemistry class (AP chemistry), we can assume complete dissociation. Therefore
both Na⁺ and Cl^- have a concentration of 2.0 M at equilibrium.

Because there is an acid/base component of the question, I know I need a reaction involving molarity of  H⁺ so I can eventually get pH. I can do this by writing a chemical reaction involving acid.
Cl^- + H₃O  HCl + H₂O

Now here's where I start to get lost. I know that I should be using the information about the electrical current, but I'm not sure how to do it. I've made two attempts so far:

Attempt 1: (.80 mol / .400 L) * (96845 C / mol) * (.25 C / sec) * (1 min / 60 sec) * (1 /35 min)
The problem here is that the units on the answer are L^-1, while I'm looking for mol / L.

Attempt 2: (.25 C / sec) * (60 sec / min) * (35 min / 1)
The problem here is that I end with mol, not mol / L AND this doesn't incorporate the information I have about the original concentration.

I've also considered doing an ICE problem, but I wouldn't know how to incorporate the electrochemical data.

Could anyone help point me in the right direction? Thanks!

[Borek]

There is no important chemistry in the solution itself, all that matters happens on the electrode.

What is the overall reaction equation for the electrode processes? Is there any product that can change solution pH?

[Hunter2]

You have to involve the water and to know what happens if you have an electrolysis of sodium chloride. Hint its one of the common industrial method to make chlorine gas and sodium hydroxide.

Your approach is on the right way.

[Arkcon]

Because there is an acid/base component of the question, I know I need a reaction involving molarity of  H⁺ so I can eventually get pH. I can do this by writing a chemical reaction involving acid.
Cl^- + H₃O  HCl + H₂O

Hmmm, I'm jumping in late, but tell me -- is this the only reaction you think will happen?  What happens at each electrode?  If a gas bubble free, is it in solution to participate in the acid-base equilibrium?