Cu(H2O)42+(aq) + 4CN-(aq) <=> Cu(CN)42-(aq) +4 H2O(l) Cu+2 is a Lewis acid as it has vacantd-orbitals that can accomodate an electron pair(Electron pairacceptor) CN- is a Lewis base as it has lone pair ofelectron that is donated to Cu+2 in the reaction(Electron pair donor) H2O is a Lewis base as the Oxygen atom haslone pair of electrons and therefre, it acts as an electronpair donor. Solution Cu(H2O)42+(aq) + 4CN-(aq) <=> Cu(CN)42-(aq) +4 H2O(l) Cu+2 is a Lewis acid as it has vacantd-orbitals that can accomodate an electron pair(Electron pairacceptor) CN- is a Lewis base as it has lone pair ofelectron that is donated to Cu+2 in the reaction(Electron pair donor) H2O is a Lewis base as the Oxygen atom haslone pair of electrons and therefre, it acts as an electronpair donor..