Electrochemistry Flashcards
What is an electrolyte?
An electrolyte is an aqueous solution of an ionic substance or a molten ionic salt that has mobile ions present (so it can conduct electricity).
What is electrolysis?
Electrolysis is a chemical process where an electric current is used to provide energy for the decomposition of an ionic salt.
Anode? What reaction happens?
The anode is the positive electrode as it is connected to the positive terminal of the cell/battery. Negative ions (anions) give up electrons to the anode to become atoms/molecules. This is oxidation.
Cathode? What reaction happens?
The cathode is the negative electrode as it is connected to the negative terminal of the cell/battery. Positive ions (cations) gain electrons from the cathode to become atoms/molecules. This is reduction.
Why is it important to take into consideration whether an electrolyte is a molten salt or an aqueous solution of a salt when predicting the products of electrolysis?
Any aqueous salt solution contains ions from water as well as ions from the salt. A selective discharge of ions occurs during electrolysis: H+ and OH- ions may gain/lose electrons instead of the ions from the salt.
In the electrolysis of an aqueous salt solution, how can you predict which positive ions will be discharged and turned into atoms/molecules?
The positive ions that can more easily gain electrons are discharged.
>Highly reactive metals lose electrons more easily than they gain them, so hydrogen will be discharged instead.
>Metals less reactive than hydrogen will be discharged.
In the electrolysis of an aqueous salt solution, how can you predict which negative ions will be discharged and turned into atoms/molecules?
The negative ions that can more easily lose electrons will be discharged.
>Halides will be discharged - if there is no halide present, hydroxide (OH-) will be discharged.
>SO-4 and NO-3 are never discharged.
>If the solution is very dilute, OH- will be discharged.
