Why will OH- not discharge?
2 Answers
Chlorine gas at the anode. We can test it by taking a piece of damp blue litmus paper, and then it will turn red, and finally bleach it white.
Explanation:
At the anode, oxidation happens. In hydrochloric acid, there exist hydrogen cations and chlorine anions. In an electrolytic cell, the anode is positive, and the cathode is negative. So, the anions will stick to the anode, and therefore chlorine here becomes oxidized.
The half equation is:
The test for chlorine gas is relatively simple. It is a greenish-yellowish gas, like sulfur and fluorine. To test for it, hold a piece of damp blue litmus paper over the gas. It should turn red and then white after a few seconds/minutes. This is due to the formation of hydrochloric acid
From what I think is that hydrochloric acid is a stronger electrolyte than water, and so chlorine is discharged more easily than hydroxide ions from water. Hydroxide ions and hydrogen ions partially dissociate in water, and will reform quite easily, but in hydrochloric acid, the ions themselves split really strongly, and maybe even to the point of no combination back.
The concentration of
Explanation:
At the anode
One might be tempted to predict that oxygen will evolve at the anode of this electrolysis cell. Comparing either species' tendencies to be oxidized under standard conditions will indeed yield this conclusion.
Behaviors of both
Dissolving a strong acid like
Recall that standard conditions demand molarity of
References
[1] Chua, Sean. “O Level Chemistry – Strategies to Predict Products of Electrolysis for Aqueuous Solutions.” SimpleChemConcepts, 28 Sept. 2008, www.simplechemconcepts.com/o-level-chemistry-strategies-to-predict-products-of-electrolysis-for-aqueuous-solutions-2/.
[2] Brown, Phil. “ELECTROLYSIS of HYDROCHLORIC ACID.” Doc Brown's Chemistry KS4 Science–Chemistry GCSE/IGCSE/O Level/A Level Revision, www.docbrown.info/page01/ExIndChem/electrochemistry07.htm.