Explain the rate difference between the reactions of 1-chlorobutane and 2-chloro-2-methylpropane using sodium iodide. 

Provide a reasonable mechanism for the reaction of 2-chloro-2-methylpropane with ethanolic silver nitrate. 

For some Sjvj2 reactions, sodium iodide can be used as a catalyst. Explain why this is the case (think about the iodide as both a nucleophile and a leaving group to help you develop a reasonable answer).