What happens to paper chromatography in you leave it in water for too long?

Nothing, really, the paper itself just gets wet and thats it. One thing to be careful of is, though, is that the dye/pigment can get too diluted and it would be hard to distinguish each of them from each other.

The activity series is shown in the attached picture. if the element is below the other, then you can displace the other. following the activity series as a guide, the reactions are as follows: nickel and aluminum chloride3 ni + 2 alcl₃  → 3 nicl₂ + 2 albarium and copper bromideba + cubr  →  no reaction because cu is less oxidizable than bapotassium nitrate and aluminum3 kno₃ + al  → al(no₃)₃ + 3 ksodium phosphate and zincnaso₄ + zn  → znso₄ + na

Answer (b) supersaturation;