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.

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.