Write the cell reaction of a lead storage battery when it is discharged. How does the density of the electrolyte change when the battery is discharged?

${\left(\frac{C^{14}}{C^{12}}\right)}_t=\frac{{\left(\frac{C^{14}}{C^{12}}\right)}_{t=0}}{{\left(2\right)}^n}$

n = 3

t = 3 * 1580

= 4740 years

The following are the real-world applications of electrochemistry - military applications such as thermal batteries, digital watches, hearing aids, digital cameras, electrical appliances such as cellphones, and torches.

It depends on students. Though it is not a tough chapter to study but for students who have misconceptions and those who struggle with visualization can find it challenging. 

There are two types of electrochemical cells - Electrolytic and Galvanic or Voltaic cells. The electrolytic cells need an external source such as AC power source or DC battery and it involve non-spontaneous reactions. The galvanic cells gets its energy from redox reactions which is spontaneous.

Redox reactions is the basic principle of the electrochemistry. The redox reactions is the process where electrons are transferred between substances. In this process chemical energy gets converted into electrical energy and vice versa.