What is salt-bridge?

Answer 1

A salt bridge is used in electrochemical voltaic cells. A salt bridge is usually an inverted glass U-tube that connects two beakers together. The salt bridge is filled with a solution of salt; potassium nitrate (KNO3) is frequently used as the salt. Other salt bridges may be filter paper that is saturated with potassium nitrate. The U-tube is plugged on both ends with glass wool or porous plugs. The salt solution does not interfere with redox reactions that take place within a voltaic cell.

Let us use for example the voltaic cell: Zn|Zn2+Cu2+|Cu

If the Cu2+ ions came in contact with the Zn electrode, the cell would short-circuit. The salt bridge prevents this from happening by completing the circuit. In a way, the salt bridge acts as a screen. As the current is drawn from the cell, metal from the left hand electrode (anode) loose electrons and go into solution. The electrons travel through external wire to right hand electrode ( cathode). Here the metal ions take electrons and deposit as metal. The salt solution in the salt bridge uses its own anions (NO3-), and its own cations (K+) to substitute for the change in charges at the anode & cathode.

Answer 2

salt bridge is