A 4.00-liter container is divided into two equal parts, one part containing 0.0100 mole of neon, and the other part containing 0.0100 mole of helium. The divider is removed and the gases mix. What is the change in entropy (in J/K) of this system

Google it that might work

The mass has escaped into a gas which you can not see so the law stays true.

Caso4(s) < > ca+2 + so4^-2 ksp = [ca+2][so4^-2] = 2.4 x 10^-5 = [0.20][so4^-2] [so4^-2] =1.2 x 10^-4 ag2so4(s) ,> 2ag+ + so4^-2 ksp = [ag+]^2[so4^-2] = 1.5 x 10^-5 = (0.30)^2[so4^-2] [so4^-2] = 1.5 x 10^-5/0.09 = 1.7 x 10^-4 caso4 would precipitate first since it requires less so4^- to form a saturated solution.  i believe this is right, i hope it !