How many moles of water are produced if 5.43 mol PbO2 are consumed

Then it can be easily concluded that 10.86 moles of water will be produced.

c. because step up transformer steps up the input voltage i.e increases the input voltage  

the number of turns are greater on the secondary side of step up transformer  

transformer does not handle dc current

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