Is lead chloride ( pbcl2) solution, substance, homogenous mixture ir heterogeneous mixture?

Lead chloride solution is A SUBSTANCE.
 In chemistry, all matters are divided into mixtures and pure substances. The pure substances are made up of one type of particle while the mixtures are made up of different particles. The pure substances can be in form of an element or a compound. Lead chloride for instance is a compound and is a pure substance.

Determine the  wavelength of light emitted when an electron  in an li2+ ion  makes a transition from an orbital with n  =  6 to an orbital with n  = 5.