Na2CrO4 + PbCL2
Formula in double replacement

Na₂CrO₄ + PbCl₂ → PbCrO₄ + 2 NaCl

Explanation:

In a double displacement reaction, the reactants which are involved in the reaction exchanging their ions thereby produces 2 new compounds. Here sodium chromate and lead chloride are undergoing double displacement reaction, the ions exchanges their position there by forming sodium chloride and lead chromate. So the double displacement reaction is given as,

Na₂CrO₄ + PbCl₂ → PbCrO₄ + 2 NaCl

i believe the answer is three water molecules