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Statistics Help

**Question: **Oxidation and reduction?

This is the first time i have come across a question like this:The following equation summarises the reactions that occur during discharge and

charging of the nickel-cadmium battery.

2NiOOH + Cd + 2H2O <(charge) --- (discharge)> 2Ni(OH)2 + Cd(OH) 2

Which of the following occurs during discharge?

(A) Ni2+ is oxidised to Ni3+

(B) Ni2+ is reduced to Ni3+

(C) Ni3+ is oxidised to Ni2+

(D) Ni3+ is reduced to Ni2+

Ok, I KNOW that it cannot be b or c because of OIL and RIG

What happens during the charging and discharging of a battery in terms of redox reactions

Please explain

p.s. the answer is D

i've asked the answer before, so please dont just tell me the answer is D, that is not being helpful

i need someone TO EXPLAIN what happens during discharging and charging a battery.

and i know that NiOOH is converted to Ni(OH)2 - but how do i know what the valency is for each?? Edit

**Answer: **This battery uses nickel oxide in its positive electrode (cathode), a cadmium compound in its negative electrode (anode), and potassium hydroxide solution as its electrolyte. The Nickel Cadmium Battery is rechargeable, so it can cycle repeatedly. A nickel cadmium battery converts chemical energy to electrical energy upon discharge and converts electrical energy back to chemical energy upon recharge. In a fully discharged NiCd battery, the cathode contains nickel hydroxide [Ni(OH)2] and cadmium hydroxide [Cd(OH)2] in the anode. When the battery is charged, the chemical composition of the cathode is transformed and the nickel hydroxide changes to nickel oxyhydroxide [NiOOH]. In the anode, cadmium hydroxide is transformed to cadmium. As the battery is discharged, the process is reversed, as shown in the following formula.

Cd + 2H2O + 2NiOOH —> 2Ni(OH)2 + Cd(OH)2

Cathode: 2NiO(OH) + 2H2O+ 2e-→2Ni(OH)2+ 2OH-

Anode: Cd + 2OH-→Cd(OH)2+ 2e-

Overall: 2NiO(OH) + Cd + 2H2O→2Ni(OH)2+ Cd(OH)2 Edit

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