ksp

Hi Guys, I'm confused how they solve for Ksp valvue Ksp = S(2s)^2 = S(4s^2) Ksp = 4S^3 I don't get the second step how did they end up with S(4S^2)? and what happen to [M]? Please help Thanks

Question: Solid silver chloride (Ksp=1.8x10-10) was added to the vascular fluid in order to increase its osmotic pressure. How much of the silver chloride can be added to solution before the vascular fluid becomes contaminated with silver chloride precipitant In the passage it states that...