The chemical equation Zn + Pb(NO3)2 refers to solid zinc added to a solution of lead nitrate, which produces solid lead and a solution of zinc nitrate. The balanced equation is Zn + Pb(NO3)2 -> Pb + Zn(NO3)2.
For example, 1 gram of zinc is dropped into 10 milliliters of a lead nitrate solution. The reaction produces a clear yellow solution and solids at the bottom of the test tube. The essential reaction trades zinc for lead, as lead precipitates out of the solution in the presence of zinc.
Lead nitrate is a colorless or white powder. Unlike other lead compounds, it is soluble in water. Zinc nitrate is a white powder that's commonly used as a mordant in dying clothing.