Although Cu+ does not exist in solution state but CuCl(s) is formed in the presence of Cl- ions in an solution of Cu(s) & Cu+2. Explain

Cu+ is not stable in aqueous solution because it undergoes Disproportionation. In this reaction the oxidation state of reactant in one product increase and in other it is decrease. Cu+= Cu + Cu2+. We can see that oxidation state of Cu+ decrease in Cu and increase in Cu2+. And when we prepare CuCl than the Cu present in the reacting species follow the above equation and due to which Cl- ion combine with copper ion to form CuCl.