Give reason :
(i) Rusting of iron pipe can be prevented by joining it with a piece of magnesium.
(ii) Conductivity of an electrolyte of an electrolyte solution decreases with the decreases in concentration.

Explanation

(i) This occurs due to the cathodic protection in which magnesium metal is oxidised (or corroded) in preference to iron since its reduction potential is lower. It acts as anode and protects iron from getting rusted.
`Mg^(2+)(aq)+2e^(-) to Mg(s),E^(@)=-2.37" V"`
`Fe^(2+)(aq)+2e^(-) to Fe(s), E^(@)=-0.44" V"`
(ii) With decrease in the concentration or upon dilution, the number of ions present per unit volume of the solution also decrease.As a result, the conductivity of the solution decreases.