TBR Electrochemistry

[DPTinthemaking15]

Alright, this comes from the newest version of TBR General Chemistry Part I. It is found in Electrochemistry Phase II, #9. "To reduce the observed voltage reading on a pH meter, which of the following should be added to solution? A.) HCl B.)NH3 C.) NaOH D.) KCl" The correct answer is A. because as TBR states, Reducing the pH requires making the solution more acidic. Increased acidity results from an increase in the H+.

I 100% understand that adding HCl into solution will reduce the pH value, but they didn't ask for that value (unless I am misinterpreting the question). They asked what would reduce the voltage reading. If you decrease the H+ in solution, would that decrease the voltage as well? I assumed the more acidic the environment is, the stronger the voltage would be.

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[CommyO]

Was there a half-reaction given in your TBR book? I remember this question from somewhere (not TBR) and essentially the addition of protons into the solution will raise the voltage for the oxidation reaction. Therefore the net voltage would go down when you consider E = Ecathode - Eanode

Cathode = reduction
Anode = oxidation

 

[PlsLetMeIn21]

I haven't gotten to that question yet, but are they talking about the pH meter reaction? I recall something like this from gen chem class and the H+ shifts the reaction in the bulb of the meter. A greater [H+] means a lower voltage reading in the cell. When I see this question, "observed voltage reading" it seems like they are asking about the reaction of the cell in the pH meter.