calculate the molarity of a solution made by dissolving 346g ofcopper 2 chloride in 2500ml of water?

Molar mass of CuCl₂ = (63.5 + 35.5×2) g/mol = 134.5 g/mol
No. of moles of CuCl₂ dissolved = (346 g) / (134.5 g/mol) = 2.57 mol
Molarity of CuCl₂ = (2.57 mol) / (2500/1000 L) = 1.03 M

You cannot tell. Molarity is moles of solute per liter of SOLUTION. The CuCl2 will assuredly increase the volume of the 2.5L of solvent. How much? We need the solution density.