Iodoform gives the precipitate with AgNO3 on heating while chloroform does not. Give reasons?

Well the covalent bond between chlorine and carbon will of greater strength than between iodine and carbon, since chlorine has a greater electronegativity and so is attracted to the bonded pair of electrons more strongly than iodine and so iodine will be able to be donated to the AgNO3 and react to form the AgI precipitate much more readily.