Observation about Electrolysis:

a) Electric current is used to drive a non-spontaneous reaction
Electrolysis is a process in which an electric current is used to drive a non-spontaneous chemical reaction. It involves the decomposition of a compound into its constituent elements or ions using an electric current. This process is used to produce various useful substances and is widely used in industries such as metallurgy, electroplating, and water electrolysis.

b) Ecell is positive and G is negative
The statement that "Ecell is positive and G is negative" is not correct. In electrolysis, the cell potential (Ecell) can be either positive or negative, depending on the specific reaction and the direction of electron flow. The sign of Ecell determines the direction of the reaction. If Ecell is positive, the reaction will proceed in the forward direction (electrons flow from anode to cathode), and if Ecell is negative, the reaction will proceed in the reverse direction (electrons flow from cathode to anode). The Gibbs free energy (G) for electrolysis is generally positive, as it requires energy input to drive a non-spontaneous reaction.

c) Cations and anions are discharged at the cathode and anode respectively
During electrolysis, cations (positively charged ions) are discharged at the cathode (negative electrode), and anions (negatively charged ions) are discharged at the anode (positive electrode). This is because opposite charges attract each other, and the cathode attracts cations while the anode attracts anions. This discharge of ions leads to the decomposition of the compound into its constituent elements.

d) Overvoltage is responsible for a particular reaction takes place
Overvoltage refers to the extra potential difference required to overcome the resistance at the electrode-electrolyte interface during electrolysis. It is responsible for a particular reaction to take place by ensuring that the desired reaction occurs at the electrode instead of other unwanted side reactions. Overvoltage depends on factors such as the nature of the electrode material, concentration of the electrolyte, and reaction conditions. By controlling the overvoltage, it is possible to selectively drive specific reactions during electrolysis.

In summary, the correct observations about electrolysis are:

- Electric current is used to drive a non-spontaneous reaction
- Cations and anions are discharged at the cathode and anode respectively
- Overvoltage is responsible for a particular reaction to take place.