When 200. ml of water are added to 100. ml of 12% kcl solution the final concentration of kcl is (assume the volumes

Since the original concentration is expressed in terms of mass %, let's also answer with mass %. To do this easily, let's use the formula for mass dilution.

C₁V₁ = C₂V₂
where C stands for concentration and V stands for volume

The solution is as follows:
(12%)(100 mL) = (C₂)(100 mL + 200 mL)
Solving for C₂,
C₂ = 4%

The density would be 1.622