Ksp for CaSO4 is 6.1E-5. How many grams of CaCl2 must be added to 500 mL of 0.010 M H2SO4 to just start precipitation of CaSO4?
-
CaSO4 = 6.1x10^-5 = [Ca2+][SO4 2-]
[Ca2+] = [sO4 2-] = 7.81x10^-3M
for ppt to start Qsp = Ksp
xmoles CaSO4 / 0.5L =7.81x10^-3M
moles CaSO4 = 3.9x10^-3moles
3.9x10^-3moles x 110.9g/mole = 0.43g CaCl2 required
[Ca2+] = [sO4 2-] = 7.81x10^-3M
for ppt to start Qsp = Ksp
xmoles CaSO4 / 0.5L =7.81x10^-3M
moles CaSO4 = 3.9x10^-3moles
3.9x10^-3moles x 110.9g/mole = 0.43g CaCl2 required