What is the purpose of a salt bridge in a voltaic cell consisting of separate breakers? Why is a salt bridge unnecessary in a single-breaker voltaic cell in which the compartments are separated by a porous divider?

1. The salt bridge completes the circuit of the voltaic cell to allow the flow of current

2. The porous divider performs the function of a salt bridge, hence a salt bridge is unnecessary in a single-beaker voltaic cell

Explanation:

1. The oxidation and reduction half cells of a voltaic cell are connected by the salt bridge in other to ensure that the internal circuit is electrically neutral, to avoid the rapid reaction to reach equilibrium conditions which affects results in preventing voltage drop in the voltaic cell.

The salt bridge also aids in charge accumulation

2. In a single-beaker voltaic cell with the compartments separated by a porous divider, the function of the porous divider is the same as that of the salt bridge, hence the salt bridge is unnecessary.

A salt bridge is a strong electrolytes and it's ion like KNO3, Consider a voltaic cell with two paths the anode half cell and the cathode half cell, it will be observed that when the cell is connected, electrons leaves through the wire from the anode which is subject to oxidation hence producing both electrons and positive ions in the anode, if more of the electrons leaves the anode, need arises to to ensure electrochemical neutrality in the cell, this is we're the salt bridge is much important because it provides the needed negative ions to counter balance the effect of this, also a reversed process occurs in the second half Cathodoc cell.

Also for a simply voltaic cell separated by a porous membrane the salt bridge is not needed because unlike the half cell connected by a salt bridge the porous membrane servea as a media of exchange of ions for the cells.